CN108645885B - Large-scale soil mass water-heat-force-salt four-field coupling effect test system and method - Google Patents

Large-scale soil mass water-heat-force-salt four-field coupling effect test system and method Download PDF

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CN108645885B
CN108645885B CN201810513020.7A CN201810513020A CN108645885B CN 108645885 B CN108645885 B CN 108645885B CN 201810513020 A CN201810513020 A CN 201810513020A CN 108645885 B CN108645885 B CN 108645885B
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soil body
water
reaction plate
temperature
salt
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CN108645885A (en
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魏海斌
李清林
贾江坤
韩雷雷
张仰鹏
王富玉
陈昭
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Jilin University
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Jilin University
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N25/00Investigating or analyzing materials by the use of thermal means
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/24Earth materials

Abstract

The invention discloses a large-scale soil body water-heat-force-salt four-field coupling effect test system and a method, which relate to the field of geotechnical soil body indoor freeze thawing test research and comprise a loading frame, a loading system, a water supplementing system, a temperature control system, a data acquisition and control system and a forming system; the loading system applies axial load and confining pressure to the soil body, the water supplementing system can simulate different salt contents and water heads to supplement the soil body, the temperature control system realizes freeze-thaw circulation of the soil body and constant-temperature water supply of the water supplementing system, the data acquisition and control system monitors the temperature, water salt distribution, pressure, pore water pressure and vertical and horizontal deformation of the soil body, the gas pressure of the gas pressure chamber is monitored in real time, data acquisition and imaging processing are controlled, and the forming system tamps and molds the designed soil material into the soil body used for the test. The invention realizes the soil body freezing and thawing process experiment of indoor water-heat-force-salt four-field coupling effect, and provides support for the research of the soil body freezing and thawing experiment.

Description

Large-scale soil mass water-heat-force-salt four-field coupling effect test system and method
Technical Field
The invention relates to the field of indoor freeze-thaw test research of a soil body, in particular to a large-scale soil body water-heat-force-salt four-field coupling effect test system and method.
Background
The seasonal frozen soil is a soil layer frozen in winter and melted in summer, the frozen soil is mainly distributed in regions where Heilan-Lai mountain is west in China, and regions where east is the line and Qinling mountain is the north of Huaihe river approximately account for 53% of the area of the national soil in China, and meanwhile, a large area of saline soil is distributed in the seasonal frozen soil range; the weather environment with periodically changed air temperature in the frozen saline soil area causes the soil body in the area to have serious frost heaving, thawing sinking, salt heaving, grout turning and other diseases, and seriously threatens the safety and stability of the soil body such as a foundation, a roadbed and the like. Although the disease phenomena are different, the disease phenomena can be classified into comprehensive action results of a soil moisture field, a temperature field, a stress field and a salt field, so that the water-heat-force-salt coupling action mechanism of the soil is researched, the soil disease control strategy of the seasonal frozen saline soil area is provided, and the method has important significance for improving the safety and the stability of the saline soil in the seasonal frozen area.
At present, the research on the water-heat-force-salt four-field coupling effect test of the soil body mainly focuses on field monitoring and indoor tests, the field observation period is too long, the cost is high, the environmental condition is difficult to control, the monitoring result is difficult to be used for scientific research with extremely high requirement on data precision, and the reported indoor tests of the water-heat-force-salt four-field coupling effect of the relevant soil body have the following defects: the test soil is mostly small-scale soil (the length, width and height are more than 50 cm); the lateral displacement of the soil body cannot be monitored and lateral confining pressure cannot be applied by filling the soil material with a cylindrical rigid barrel or a square box; the heat insulation material is used for heat insulation, although the heat insulation material has a certain heat insulation function, the heat insulation material is still a heat conduction material, so that the temperature loss of the test system cannot be effectively controlled.
Therefore, the design of the test system and the method for the large-scale soil body water-heat-force-salt four-field coupling effect, which can provide axial load and lateral confining pressure, have good heat preservation performance and can monitor the lateral deformation of the soil body, have important significance for scientific research and engineering construction.
Disclosure of Invention
The embodiment of the invention provides a large-scale soil water-heat-force-salt four-field coupling effect test system which can provide axial load and lateral confining pressure, has good heat preservation performance and can monitor the lateral deformation of a soil body.
The embodiment of the invention provides a large-scale soil mass water-heat-force-salt four-field coupling effect test system, which comprises: the system comprises a loading frame, a loading system, a water supplementing system, a temperature control system, a data acquisition and control system and a forming system; the loading frame includes: the device comprises a support column, a first reaction plate, a second reaction plate, a third reaction plate, a first high-strength screw rod and a second high-strength screw rod; at least one first high-strength screw rod is arranged between the second reaction plate and the third reaction plate, the third reaction plate is positioned above the second reaction plate, at least one support column is arranged on the bottom surface of the second reaction plate, the bottom end of the second high-strength screw rod penetrates through the second reaction plate, the position close to the bottom end is fixed on the second reaction plate through a first sealing nut, the top end of the second high-strength screw rod penetrates through the first reaction plate, the position close to the top end is fixed on the first reaction plate through a second sealing nut, and the first reaction plate is positioned above the second reaction plate and below the third reaction plate;
the loading system comprises: axial load loading equipment and lateral confining pressure loading equipment of the soil body; the axial load loading equipment of the soil body comprises a hydraulic jack and a load sensor, wherein the hydraulic jack is arranged on the bottom surface of the third reaction plate, and the load sensor is arranged on the bottom surface of the hydraulic jack; the axial load loading equipment of the soil body also comprises a servo control console arranged outside the loading frame, the servo control console is respectively connected with the hydraulic jack and the load sensor through electric connecting wires, and the servo control console is used for controlling the hydraulic jack to load and unload the soil body or maintain constant pressure, and collecting and outputting monitoring load of the load sensor; the soil body lateral confining pressure loading equipment comprises a pressure chamber for sealing a soil body in a gas pressure space, and a gas supply pipe which passes through a second reaction plate and is communicated with the pressure chamber, wherein one end of the gas supply pipe is communicated with the pressure chamber, the other end of the gas supply pipe is communicated with an air compression station, and the air compression station provides lateral confining pressure for the soil body; the pressure chamber comprises a first reaction plate bottom surface and a second reaction plate top surface, and further comprises a steel barrel arranged between the first reaction plate bottom surface and the second reaction plate top surface; a first sealing piston sleeve is arranged in the middle of the first reaction plate, and a force transmission shaft is arranged in the center of the first sealing piston sleeve;
the water charging system comprises: the device comprises a Mariotte bottle, a water inlet pipe, a first permeable stone, a second permeable stone, a water outlet pipe and a first glass pipe; the first permeable stone and the second permeable stone are respectively arranged at the bottom of the soil body, the first permeable stone and the second permeable stone are arranged on the same horizontal plane, two ends of the water inlet pipe are respectively communicated with the water outlet of the March flask and the first permeable stone, and two ends of the water outlet pipe are respectively communicated with the second permeable stone and the first glass pipe; the March's bottle consists of a second glass tube, a bottle body and a rubber plug, the rubber plug plugs the bottle body, and the glass tube penetrates through the rubber plug and is communicated with the inner space and the outer space of the March's bottle;
the temperature control system includes: a temperature supply device and a temperature preservation device; the temperature supply equipment comprises a lower constant temperature plate, a bottom cooling liquid circulating pipe and a bottom constant temperature groove, wherein the lower constant temperature plate is contacted with the bottom surfaces of the first permeable stone and the first permeable stone, the bottom cooling liquid circulating pipe is communicated with the lower constant temperature plate, the bottom constant temperature groove is communicated with the bottom cooling liquid circulating pipe, and the lower constant temperature plate, the bottom cooling liquid circulating pipe and the bottom constant temperature groove form a closed circulating system; the constant temperature system also comprises an upper constant temperature plate arranged on the top surface of the soil body, a top cooling liquid circulating pipe communicated with the upper constant temperature plate, and a top constant temperature groove communicated with the top cooling liquid circulating pipe, wherein the upper constant temperature plate, the top cooling liquid circulating pipe and the top constant temperature groove form a closed circulating system; the purpose of applying different temperature gradients to the soil body is realized by setting different working temperatures for the bottom thermostatic bath and the top thermostatic bath; the temperature supply equipment also comprises a constant temperature box, a first temperature probe and a second temperature probe, the Mariotte bottle is arranged in the constant temperature box, the bottle body is coiled with a bottom cooling liquid circulating pipe, and a control panel and the first temperature probe are arranged on the constant temperature box; the first temperature probe monitors the working temperature of a thermostat, the working temperature of the thermostat is set to be the same as that of the bottom thermostatic bath, and the second temperature probe is arranged in the Martensis bottle;
the heat preservation device comprises: the vacuum chamber comprises a first vacuum chamber positioned at the upper part of the pressure chamber, a second vacuum chamber positioned at the lower part of the pressure chamber and a third vacuum chamber positioned at the side surface of the pressure chamber;
the first vacuum chamber, the second vacuum chamber and the third vacuum chamber are communicated through a plurality of communicating pipes, the first vacuum chamber is communicated with a vacuumizing pipe, the vacuumizing pipe is communicated with a vacuumizing pump, and vacuum environments of the first vacuum chamber, the second vacuum chamber and the third vacuum chamber are manufactured by switching on the vacuum pump;
the data acquisition and control system comprises: the system comprises a sensor group, a data acquisition box and a workstation; the sensor group comprises a displacement meter for monitoring the integral deformation of the soil body, a laser ranging sensor for monitoring the lateral deformation of the soil body, a water salt sensor for monitoring the moisture and salt content of the soil body, a pore water pressure sensor for monitoring the pore water pressure of the soil body, a soil pressure box for monitoring the vertical stress field change of the soil body, and gas pressure sensors for monitoring the gas pressure in the pressure chamber, the first vacuum chamber, the second vacuum chamber and the third vacuum chamber; the data acquisition box is used for acquiring data monitored by the sensor group, the workstation is used for analyzing and processing the acquired data, and the workstation comprises a microcomputer and data processing software;
the forming system includes: the first forming protection barrel is arranged on the second reaction plate, the second forming protection barrel is arranged on the upper portion of the first forming protection barrel, the third forming protection barrel is arranged on the upper portion of the second forming protection barrel, rubber films are tightly attached to the inner walls of the first forming protection barrel, the inner walls of the second forming protection barrel and the inner walls of the third forming protection barrel, flanges are respectively arranged on the outer walls of the second forming protection barrel and the outer walls of the third forming protection barrel, screw fixing grooves are formed in the flanges, screw fixing holes are formed in the second reaction plate, a third high-strength screw sequentially passes through the screw fixing holes in the second reaction plate, and the first forming protection barrel, the second forming protection barrel and the third forming protection barrel are fixed through the screw fixing grooves in the flanges; each screw fixing groove and the high-strength screw are fixed through a first nut, and the forming system further comprises compaction equipment for compacting designed soil to form a soil body and a tightening rubber sleeve on the side face of the rubber film.
Preferably, a second sealing rubber ring and a supporting screw are uniformly arranged between the first steel cover and the first reaction plate and between the second reaction plate and the second steel cover, and the supporting screw is a high-strength steel screw with threads;
the second reaction plate and the first high-strength screw rod as well as the third reaction plate and the first high-strength screw rod are fixed through second nuts;
third sealing rubber rings are uniformly arranged between the first reaction plate and the first steel barrel, between the first reaction plate and the second steel barrel, between the second reaction plate and the first steel barrel and between the second reaction plate and the second steel barrel;
fourth sealing rubber rings are uniformly arranged between the first sealing nut and the second counter-force plate, between the second sealing nut and the first counter-force plate, between the third sealing nut and the first steel cover and between the fourth sealing nut and the second steel cover.
Preferably, the second steel cover, the second reaction plate and the lower thermostatic plate are all provided with threaded through holes matched with sealing screws, and the sealing screws are hollow screws and used for data transmission lines and bottom cooling liquid circulating pipes, and water inlet pipes and water outlet pipes penetrate through the hollow screws;
a water stop clamp for controlling the flow of the Ma bottle is arranged on the water inlet pipe, and a fine sand layer covers the first permeable stone and the second permeable stone.
Preferably, the soil body is a cylindrical soil body with the diameter of 50cm and the height of 100 cm; the first reaction plate, the second reaction plate and the third reaction plate are cylindrical steel plates;
the first forming protection barrel, the second forming protection barrel and the third forming protection barrel are formed by splicing two half-moon-shaped steel barrels, so that the first forming protection barrel, the second forming protection barrel and the third forming protection barrel are easy to remove after a soil body is manufactured; the side walls of the first forming protection barrel, the second forming protection barrel and the third forming protection barrel are provided with air exhaust holes.
Preferably, the upper thermostatic plate and the lower thermostatic plate are both composed of cylindrical steel plates, and a part of the top cooling liquid circulating pipe entering the pressure chamber penetrates through the force transmission shaft; go up the thermostated plate and all be provided with the recess with lower thermostated plate side, through tighten the rubber sleeve, go up the recess on thermostated plate and the lower thermostated plate and closely laminate rubber membrane, last thermostated plate and lower thermostated plate, prevent that the part of the soil body drops and the gas in the pressure chamber from invading the soil body during the test.
Preferably, the number of the gas pressure sensors, the number of the laser ranging sensors, the number of the soil pressure boxes, the number of the pore water pressure sensors and the number of the water salt sensors are 4, the number of the laser ranging sensors, the number of the soil pressure boxes and the number of the pore water pressure sensors are respectively arranged on the same vertical line, the vertical interval is 20cm, and the number of the 4 gas pressure sensors are respectively arranged in the first vacuum chamber, the second vacuum chamber, the third vacuum chamber and the pressure chamber; the first vacuum chamber comprises a first reaction plate top surface, a first sealing piston sleeve, a first steel cover, a second sealing piston sleeve, a first sealing rubber ring and a second sealing piston ring, wherein the first sealing piston sleeve is arranged in the center of the first reaction plate and is in fit contact with the first reaction plate and the force transmission shaft;
the second vacuum chamber comprises a second reaction plate bottom surface, a second steel cover arranged at the lower part of the second reaction plate bottom surface, and a sealing screw rod arranged at the centers of the second reaction plate and the second steel cover, wherein the sealing screw rod is in fit contact with the second reaction plate and the second steel cover, and the contact part is free from air leakage and water leakage; the bottom end of the second high-strength screw rod penetrates through the second steel cover and is fixed on the second steel cover by a fourth sealing nut;
the first steel barrel is sleeved in the second steel barrel, and the interval formed by the outer wall of the first steel barrel and the inner wall of the second steel barrel is the third vacuum chamber.
Preferably, the gas pressure sensor, the laser ranging sensor, the soil pressure cell, the pore water pressure sensor and the water salt sensor are internally provided with the temperature sensor, so that the step of independently embedding the temperature sensor into the soil body is omitted while the data effect of the temperature correction sensor is achieved.
Preferably, the mahalanobis bottle is used for bearing pure water or water with different salinity, the bottom of the load sensor is in contact with the top surface of a force transmission shaft of the pressure chamber, and a force transmission steel plate is arranged between the force transmission shaft and the upper thermostatic plate.
Preferably, the axial load loading equipment of the soil body in the loading system further comprises a limiting device for positioning the force transmission shaft, a limiting hole is arranged on the force transmission shaft, the limiting device comprises a limiting screw rod, a combined nut and a screwing screw rod, the limiting screw rod is vertically fixed at the bottom of the third reaction plate through threads, the combined nut is sleeved on the limiting screw rod and is controlled to ascend and descend in position through rotation of the threads, the bottom of the combined nut is a nut with a horizontal channel, the nut with the horizontal channel can freely rotate in the horizontal direction, and the screwing screw rod can freely screw on the nut with the horizontal channel at the bottom of the combined nut until the screwing screw rod is in fit contact with the limiting hole prefabricated on the force transmission shaft.
The embodiment of the invention provides a soil mass water-heat-force-salt four-field coupling effect test method based on a large-scale soil mass water-heat-force-salt four-field coupling effect test system, which is characterized by comprising the following steps of:
step 1, starting a data acquisition and control system, starting to acquire temperature, water salt, stress and pore water pressure information in a soil body, acquiring lateral and vertical deformation information of the soil body, acquiring gas pressure information in a first vacuum chamber, a second vacuum chamber and a third vacuum chamber, and acquiring loading and unloading information of a hydraulic jack on the soil body;
step 2, keeping the water inlet pipe, the water outlet pipe and the glass pipe unblocked, starting a loading system, setting working parameters of a servo control table through a workstation, enabling the hydraulic jack to work until a force transmission shaft is contacted with a force transmission steel plate, adjusting the air supply pressure of an air compression station to enable the air pressure in a pressure chamber to reach a design value, setting the working parameters of the servo control table through the workstation again, and enabling the hydraulic jack to perform constant-load consolidation on a soil body until the consolidation of the soil body is stable;
step 3, after the consolidation of the soil body is completed, fixing the force transmission shaft through a limiting device for positioning the force transmission shaft, and limiting the displacement of the force transmission shaft, so that the rigid constraint of frost heaving of the soil body is realized;
step 4, opening a vacuum pump, and pumping the first vacuum chamber, the second vacuum chamber and the third vacuum chamber into a vacuum state through the vacuum pumping function, wherein the vacuum state takes the data of the gas pressure sensor as a judgment basis;
step 5, opening the bottom thermostatic bath, setting the working temperatures of the bottom low-temperature thermostatic bath and the thermostat according to the groundwater supply temperature to be simulated, starting an external circulating pump of the bottom thermostatic bath after the bottom thermostatic bath reaches the working temperature, and heating or cooling the saline water in the Mariotte bottle through a bottom cooling liquid circulating pipe and the thermostat until the temperature of the temperature probe displayed by the control panel reaches a design value and is stable;
step 6, opening a water stop clamp on the water inlet pipe to supply water, enabling salt-containing water in the Martin bottle to enter a fine sand layer, and discharging gas from a graduated glass pipe communicated with the fine sand layer; when the gas is completely exhausted, adjusting the position of the Mariotte bottle to enable the bottom of the glass tube in the Mariotte bottle and the top of the fine sand layer to be on the same horizontal plane, and simulating a constant underground water level to supply a soil body;
step 7, starting the top thermostatic bath, starting an external circulating pump of the top thermostatic bath when the working temperature reaches a design value, enabling a low-temperature medium in the top thermostatic bath to pass through a top cooling liquid circulating pipe and circulate through an upper thermostatic plate to freeze a soil body, and finishing freezing after the temperature, water salt and stress in the soil body, the pore water pressure and the lateral deformation of the soil body are stable;
step 8, adjusting the working temperature of the top thermostatic bath, setting the working temperature of the top thermostatic bath according to the temperature for melting the soil body according to the design requirement, starting an external circulating pump of the top thermostatic bath when the working temperature reaches a design value, enabling a low-temperature medium in the top thermostatic bath to circulate through a top cooling liquid circulating pipe and an upper thermostatic plate, melting the soil body, and finishing a melting test after the temperature, water salt, stress, pore water pressure and lateral deformation of the soil body in the soil body are stable;
9, if the freeze-thaw cycle test of the soil body is carried out, repeating the 7 th step and the 8 th step;
and step 10, acquiring and storing the temperature, water salt, stress, pore water pressure and lateral and vertical deformation information of the soil body in real time by a data acquisition and control system, and analyzing and imaging the acquired data by data processing software of a workstation to obtain the dynamic coupling action of water-heat-force-salt in the freezing and thawing process of the large-scale soil body.
The large-scale soil water-heat-force-salt four-field coupling effect test system provided by the invention has the following beneficial effects:
(1) the forming system can be used for compacting and forming large-scale soil (with the diameter of 50cm and the height of 100), the requirements on the size and the distance of the embedded sensor are met, and the accuracy of monitoring data is guaranteed.
(2) The invention can simulate the supply of constant-temperature constant-head groundwater with different salinity to the soil body, and is used for researching the water and salt migration rule of the large-scale soil body under the four-field coupling action.
(3) The vacuum chamber is designed to serve as a heat insulation boundary of the pressure chamber and the test environment, and the influence of the test environment temperature on the test data side is effectively reduced.
(4) The pressure chamber is designed to serve as a confining pressure providing device for the soil body, and the heat conductivity of the gas in the pressure chamber is poor, so that the formation of the temperature gradient in the freezing and thawing process of the soil body is facilitated.
(5) The combined application of the temperature control system, the loading system and the water supply system more truly simulates the freezing and thawing, stress and underground water supply environment of the foundation or the roadbed soil body in the region of the frozen saline soil in season, and provides a water-heat-force-salt coupling effect test system which is more in line with the actual situation.
(6) The system can obtain the information of vertical integral deformation, lateral deformation, water and salt content distribution, pressure distribution, temperature distribution and pore water pressure distribution in the soil body in real time, and provides technical guarantee for the research of the water-heat-force-salt four-field coupling effect of the large-scale soil body.
(7) Through the combined application of the workstation, the data acquisition box and the sensor group, the automatic acquisition and processing of test data are realized, and the reliability of data acquisition is effectively ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a functional block diagram of the present invention;
FIG. 2 is a main body structure view of the present invention;
FIG. 3 is a view showing the arrangement of the permeable stone in contact with the water inlet pipe and the water outlet pipe;
FIG. 4 is a view of the seal screw of the present invention;
FIG. 5 is a structural view of an upper thermostatic plate of the present invention;
FIG. 6 is a view showing the structure of a lower thermostatic plate according to the present invention;
FIG. 7 is a plan view of the forming system of the present invention;
FIG. 8 is a cross-sectional view of a forming system of the present invention;
figure 9 is a plan view of the sensor placement within the earth mass of the present invention.
The numbering in the drawings illustrates:
2-1 to 2-3 high-strength screw rods, 3 supporting screw rods, 4 first vacuum chambers, 5 second vacuum chambers, 6 third vacuum chambers, 7 gas pressure sensors, 8 pressure chambers, 9 laser ranging sensors, 10 soil pressure boxes, 12 pore water pressure sensors, 13 water salt sensors, 14 communicating pipes, 15 rubber membranes, 16 soil bodies, 17 top constant temperature plates, 17-1 lower bearing plates, 17-2 upper bearing plates, 17-3 closed cavities, 17-4 load supporting columns, 18 bottom constant temperature plates, 19 hydraulic jacks, 20 load sensors, 21 displacement meters, 22-1 to 22-2 permeable stones, 23 fine sand layers, 24 sealing screw rods, 24-1 outer sealing screw rods, 24-2 inner sealing screw rods and 25 water inlet pipes, 26-1, a bottom cooling liquid circulating pipe, 26-2, a top cooling liquid circulating pipe, 27, a water outlet pipe, 28, a vacuum pumping pipe, 29, a graduated glass pipe, 30, a Martin bottle, 30-1, a glass pipe, 31-1-31-2, a temperature probe, 32, a thermostat, 33, a control panel, 34, a tightening rubber sleeve, 35, a CO2 supply pipe, 36-1-36-5, a sealing rubber ring, 37-1, a first reaction plate, 37-2, a second reaction plate, 37-3, a third reaction plate, 38-1-38-2, a steel barrel, 39, a force transmission steel plate, 40-1, a first sealing piston sleeve, 40-2, a second sealing piston sleeve, 41-1-42-2, a steel cover, 42, a support column, 43, a force transmission shaft, 44, a data transmission line connector, 45, a pipeline connector, 46. the device comprises a sealing rubber gasket, 47 parts of sealing glue, 49 parts of an air suction hole, 51 parts of a flange, 52 parts of a screw positioning groove, 53-1 parts of a first forming protection barrel, 53-2 parts of a second forming protection barrel, 53-3 parts of a third forming protection barrel, 54 parts of a screw fixing hole, 55-1-55-2 parts of a nut, 56-2 parts of a limiting screw, 56-3 parts of a combined nut and 56-4 screwing screws.
Detailed Description
An embodiment of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of the present invention is not limited to the embodiment.
Fig. 1 exemplarily shows a schematic block diagram of a large-scale soil mass water-heat-force-salt four-field coupling test system provided by an embodiment of the present invention, and specifically as shown in fig. 1, the large-scale soil mass water-heat-force-salt four-field coupling test system includes: the loading system comprises a loading frame 100, a loading system 200, a water supplementing system 300, a temperature control system 400, a data acquisition and control system 500 and a forming system 600; the loading frame 100 is used for carrying the loading system 200, the water replenishing system 300, the temperature control system 400, the data acquisition and control system 500 and the forming system 600; the loading system 200 is used for applying axial load and confining pressure to the soil body 16; the water supplementing system 300 is used for simulating different salt contents and water heads to supplement the soil body 16; the temperature control system 400 is used for supplying water to the freeze-thaw cycle of the soil body 16 and the constant temperature of the water supply system, and the data acquisition and control system 500 is used for monitoring the temperature and the water salt content, the pressure, the pore water pressure, the lateral and vertical deformation information of the soil body 16, monitoring the gas pressure of the loading system 200 and the temperature control system 400 in real time, acquiring and processing the temperature and the water salt content, the pressure, the pore water pressure, the lateral and vertical deformation information of the soil body 16, and monitoring the gas pressure of the loading system 200 and the temperature control system 400; the forming system 600 is used to compact and shape pre-prepared soil into the soil mass 16 for testing.
Fig. 2 is a main structure view of the present invention, and as shown in fig. 2, the loading frame 100 includes: a strut 42, a first reaction plate 37-1, a second reaction plate 37-2, a third reaction plate 37-3, a first high-strength screw 2-1 and a second high-strength screw 2-2; at least one first high-strength screw 2-1 is arranged between the second reaction plate 37-2 and the third reaction plate 37-3, and the third reaction plate 37-3 is located above the second reaction plate 37-2, at least one supporting column 42 is arranged on the bottom surface of the second reaction plate 37-2, the bottom end of the second high-strength screw 2-2 penetrates through the second reaction plate 37-2, and is fixed to the second reaction plate 37-2 adjacent to the bottom end portion by a first packing nut, the top end of the second high-strength screw 2-2 passes through the first reaction plate 37-1, and the part near the top end is fixed on the first reaction plate 37-1 by a second sealing nut, the first reaction plate 37-1 is located above the second reaction plate 37-2 and below the third reaction plate 37-3.
In the embodiment of the invention, the loading frame provides counter force and support for the loading system, and the components of the loading frame also participate in the formation of the temperature control system, and are connected with the water supplementing system, the data acquisition and control system and the forming system, so that the loading frame is a framework of the whole test system.
In the embodiment of the invention, the soil body 16 is a cylindrical soil body with the diameter of 50cm and the height of 100cm, and the first reaction plate 37-1, the second reaction plate 37-2 and the third reaction plate 37-3 are cylindrical steel plates.
Specifically, as shown in fig. 1, the loading system 200 includes: axial load loading equipment of the soil body 16 and lateral confining pressure loading equipment of the soil body 16; the axial load loading device of the soil body 16 comprises a hydraulic jack 19 arranged on the bottom surface of the third reaction plate 37-3 and a load sensor 20 arranged on the bottom surface of the hydraulic jack 19; the axial load loading equipment of the soil body 16 further comprises a servo control console arranged outside the loading frame, the servo control console is respectively connected with the hydraulic jack 19 and the load sensor 20 through electric connecting wires, and the servo control console is used for controlling the hydraulic jack 19 to load and unload the soil body 16 or maintain constant pressure, and collecting and outputting monitoring load of the load sensor 20; the lateral confining pressure loading equipment for the soil mass 16 comprises a pressure chamber 8 for sealing the soil mass 16 in a gas pressure space, and a gas supply pipe 35 which passes through a second reaction plate 37-2 and is communicated with the pressure chamber 8, wherein one end of the gas supply pipe 35 is communicated with the pressure chamber 8, the other end of the gas supply pipe is communicated with an air compression station, and the lateral confining pressure of the soil mass 16 is provided by the air compression station; the pressure chamber 8 comprises a first reaction plate 37-1 bottom surface and a second reaction plate 37-2 top surface, and further comprises a steel barrel 38-1 disposed between the first reaction plate 37-1 bottom surface and the second reaction plate 37-2 top surface; the middle part of the first reaction plate 37-1 is provided with a first sealing piston sleeve 40-1, and the center of the first sealing piston sleeve 40-1 is provided with a force transmission shaft 43.
Fig. 3 is a layout diagram of the permeable stone of the present invention contacting with the water inlet pipe and the water outlet pipe, as shown in fig. 1 and 3, the water replenishing system 300 includes: a Mariotte bottle 30, a water inlet pipe 25, a first permeable stone 22-1, a second permeable stone 22-2, a water outlet pipe 27 and a first glass pipe 29; the first permeable stone 22-1 and the second permeable stone 22-2 are respectively arranged at the bottom of the soil body 16, the first permeable stone 22-1 and the second permeable stone 22-2 are arranged on the same horizontal plane, two ends of the water inlet pipe 25 are respectively communicated with the water outlet of the Mariotte bottle 30 and the first permeable stone 22-1, and two ends of the water outlet pipe 27 are respectively communicated with the second permeable stone 22-2 and the first glass tube 29; therefore, the first glass tube 29 can display the water supply head of the Mariotte 30 to the soil body 16, and can play a role in draining water and exhausting air in the test process.
Wherein, the water inlet pipe 25 is provided with a water stop clip for controlling the flow of the March's bottle 30, the March's bottle 30 is composed of a second glass tube 30-1, a bottle body and a rubber plug 30-2, the rubber plug 30-2 seals the bottle body, and the second glass tube 30-1 passes through the rubber plug 30-2 to communicate the inner space and the outer space of the March's bottle 30. The water in the mahalanobis bottle 30 can be pure water or water with different salinity, so that the supply of water with different salinity of the water supplementing system is realized, and the mahalanobis bottle principle of the mahalanobis bottle 30 can realize the water supply with a constant head.
In addition, in the embodiment of the present invention, the first permeable stone 22-1 and the second permeable stone 22-2 are covered with the fine sand layer 23, and the fine sand layer 23, the first permeable stone 22-1 and the second permeable stone 22-2 form a water replenishing cavity of the soil mass 16, which plays a role of water replenishing aquifer, and simultaneously plays a role of a reverse filter layer, so that the water outlet pipe 27 and the first glass pipe 29 do not block due to the entering of fine particles in the soil mass 16 when performing water draining and air exhausting.
Note that the first glass tube 29 is provided with a scale.
Specifically, as shown in fig. 1, the temperature control system 400 includes: a temperature supply device and a temperature preservation device; the temperature supply equipment comprises a lower constant temperature plate 18 contacted with the bottom surfaces of a first permeable stone 22-1 and a first permeable stone 22-2, a bottom cooling liquid circulating pipe 26-1 communicated with the lower constant temperature plate 18, a bottom constant temperature groove communicated with the bottom cooling liquid circulating pipe 26-1, wherein the lower constant temperature plate 18, the bottom cooling liquid circulating pipe 26-1 and the bottom constant temperature groove form a closed circulating system; the constant temperature system also comprises an upper constant temperature plate 17 arranged on the top surface of the soil body 16, a top cooling liquid circulating pipe 26-2 communicated with the upper constant temperature plate 17, a top constant temperature groove communicated with the top cooling liquid circulating pipe 26-2, wherein the upper constant temperature plate 17, the top cooling liquid circulating pipe 26-2 and the top constant temperature groove form a closed circulating system; the purpose of applying different temperature gradients to the soil body 16 is realized by setting different working temperatures for the bottom thermostatic bath and the top thermostatic bath; the temperature supply equipment also comprises a thermostat 32 which provides a constant temperature environment for the Mariotte bottle 30 in the water replenishing system, the Mariotte bottle 30 is arranged in the thermostat 32, a bottom cooling liquid circulating pipe 26-1 is wound on the bottle body, and a control panel 33 and a first temperature probe 31-1 are arranged on the thermostat 32; the first temperature probe 31-2 monitors the working temperature of the constant temperature box 32, the working temperature of the constant temperature box 32 and the working temperature of the constant temperature tank at the bottom are set to be the same, and the second temperature probe 31-1 is used for monitoring the temperature of the water and salt liquid in the Mariotte bottle 30 to realize constant temperature water supply of a water supplementing system; this heat preservation equipment: a first vacuum chamber 4 positioned at the upper part of the pressure chamber 8, a second vacuum chamber 5 positioned at the lower part of the pressure chamber 8, and a third vacuum chamber 6 positioned at the side surface of the pressure chamber 8; the first vacuum chamber 4, the second vacuum chamber 5 and the third vacuum chamber 6 are communicated through a plurality of communicating pipes 14, the first vacuum chamber 4 is communicated with an evacuating pipe 28, the evacuating pipe 28 is communicated with an evacuating pump, and the vacuum environment of the first vacuum chamber 4, the second vacuum chamber 5 and the third vacuum chamber 6 is manufactured by switching on the evacuating pump.
Wherein, the first vacuum chamber 4 comprises a first reaction plate 37-1 top surface, a first sealing piston sleeve 40-1 arranged in the center of the first reaction plate 37-1 and in contact with the first reaction plate 37-1 and the force transmission shaft 43 in a matching way, a first steel cover 41-1 arranged on the top of the first reaction plate 37-1, a second sealing piston sleeve 40-2 arranged in the center of the first steel cover 41-1 and in contact with the steel cover 41-1 and the force transmission shaft 43 in a matching way, a first sealing rubber ring 36-4 arranged between the first sealing piston 40-1 and the second sealing piston sleeve 40-2, and a third sealing nut which is used for fixing the top end of the second high-strength screw 2-2 on the first steel cover 41-1 after passing through the first steel cover 41-1; the second vacuum chamber 5 comprises a second reaction plate 37-2, a second steel cover 41-2 arranged at the lower part of the second reaction plate 37-2, and a sealing screw 24 arranged at the center of the second reaction plate 37-2 and the second steel cover 41-2, wherein the sealing screw 24 is in fit contact with the second reaction plate 37-2 and the second steel cover 41-2, and the contact part is airtight and watertight; the bottom end of the second high-strength screw 2-2 penetrates through the second steel cover 41-2 and is fixed on the second steel cover 41-2 by a fourth sealing nut; the first steel barrel 38-1 is sleeved in the second steel barrel 38-2, and the third vacuum chamber 6 is formed by the outer wall of the first steel barrel 38-1 and the inner wall of the second steel barrel 38-2.
The first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3 are formed by splicing two half-moon-shaped steel barrels, so that the first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3 are easy to remove after the soil body 16 is made; the side walls of the first forming protection barrel 53-1, the second forming protection barrel 53-2 and the third forming protection barrel 53-3 are all provided with air suction holes 49.
The data acquisition and control system 500 includes: the system comprises a sensor group, a data acquisition box and a workstation; the sensor group comprises a displacement meter 21 for monitoring the integral deformation of the soil body 16, a laser distance measuring sensor 9 for monitoring the lateral deformation of the soil body 16, a water salt sensor 13 for monitoring the moisture and salt content of the soil body 16, a pore water pressure sensor 12 for monitoring the pore water pressure of the soil body 16, a soil pressure box 10 for monitoring the vertical stress field change of the soil body 16, a pressure sensor 7 for monitoring the gas pressure in a pressure chamber 8, a first vacuum chamber 4, a second vacuum chamber 5 and a third vacuum chamber 6; the data acquisition box is used for acquiring data monitored by the sensor group, the workstation is used for analyzing and processing the acquired data, and the workstation comprises a microcomputer and data processing software.
In the embodiment of the invention, the sensors in the sensor group are connected with the data acquisition box through the data transmission lines, the data acquisition box is connected with the workstation through the data transmission lines, the data acquisition frequency of the data acquisition box is controlled through the workstation, the data acquisition box acquires data monitored by the sensors and transmitted by the data transmission lines, and the acquired data is analyzed and imaged by a microcomputer and data processing software of the workstation.
Further, as shown in fig. 2, 7 and 8, the forming system 600 includes: a first forming protect bucket 53-1 placed on the second reaction plate 37-2, a second forming protect bucket 53-2 placed on the upper portion of the first forming protect bucket 53-1, a third forming protect bucket 53-3 placed on the upper portion of the second forming protect bucket 53-2, the inner walls of the first forming protection barrel 53-1, the second forming protection barrel 53-2 and the third forming protection barrel 53-3 are all tightly adhered with rubber membranes 15, the outer walls are respectively provided with flanges 51, a screw fixing groove 52 is arranged on the flange 51, a screw fixing hole 54 is arranged on the second reaction plate 37-2, a third high-strength screw 2-3 sequentially passes through the screw fixing hole 54 on the second reaction plate 37-2, and the screw fixing groove 52 on the flange 51 realizes the fixation of the first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3; each screw fixing groove 52 and the high-strength screw 2-3 are fixed through a first nut 55-2, and the forming system 600 further comprises compaction equipment for compacting designed soil to form a soil body 16 and a tightening rubber sleeve 34 on the side surface of the rubber film 15.
In this example, the compaction device is a manual compaction hammer, which is divided into a weight of 2.5kg and a weight of 4.5 kg.
The first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3 are formed by splicing two half-moon-shaped steel barrels, so that the first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3 are easy to remove after the soil body 16 is made; the side walls of the first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3 are all provided with air suction holes 49, the rubber film 15 can be tightly combined with the first forming protective barrel 53-1, the second forming protective barrel 53-2 and the third forming protective barrel 53-3 through air suction, and the forming system further comprises a tightening rubber sleeve 34 which is used for tightly jointing the rubber film 15 with the upper constant temperature plate 17 and the lower constant temperature plate 18 after the soil body 16 is manufactured.
Furthermore, a second sealing rubber ring 36-3 and a supporting screw 3 are uniformly arranged between the first steel cover 41-1 and the first reaction plate 37-1, and between the second reaction plate 37-2 and the second steel cover 41-2, and the supporting screw 3 is a high-strength steel screw with threads; the second reaction plate 37-2 and the first high-strength screw 2-1 as well as the third reaction plate 37-3 and the first high-strength screw 2-1 are fixed through a second nut 55-1; third sealing rubber rings 36-1 are respectively arranged between the first reaction plate 37-1 and the first steel barrel 38-1, between the first reaction plate 37-1 and the second steel barrel 38-2, between the second reaction plate 37-2 and the first steel barrel 38-1, and between the second reaction plate 37-2 and the second steel barrel 38-2; fourth sealing rubber rings 36-2 are uniformly arranged between the first sealing nut and the second reaction plate 37-2, between the second sealing nut and the first reaction plate 37-1, between the third sealing nut and the first steel cover 41-1 and between the fourth sealing nut and the second steel cover 41-2.
Further, as shown in FIG. 4, the second steel cover 41-2, the second reaction plate 37-2 and the lower thermostatic plate 18 are all provided with threaded through holes which are engaged with the sealing screws 24, and the sealing screws 24 are hollow screws for the data transmission line, the bottom cooling liquid circulation pipe 26-1, the water inlet pipe 25 and the water outlet pipe 27 to pass through.
Specifically, as shown in fig. 4, the sealing screw 24 includes an outer sealing screw 24-1 and an inner sealing screw 24-2, which are hollow inside; the inner diameter of the outer sealing screw 24-1 is larger than the outer diameter of the inner sealing screw 24-2, and the length is shorter than that of the inner sealing screw 24-2; a bottom cooling liquid circulating pipe 26-1, a water inlet pipe 25 and a water outlet pipe 27 are arranged between the inner sealing screw 24-2 and the outer sealing screw 24-1, and pipe joints 45 are arranged at two ends of the water inlet pipe 25 and the water outlet pipe 27; a data transmission line is arranged in the inner sealing screw 24-2, and a data transmission line connector 44 is arranged at the end of the data transmission line; sealing nuts 48-2 are arranged outside the inner sealing screw 24-2 and the outer sealing screw 24-1, and sealing rubber gaskets 46 are arranged on the nuts 48-2; the interiors of the outer sealing screw 24-1 and the inner sealing screw 24-2 are sealed by a sealant 47; through the use of the data transmission line connector 44, the pipeline connector 45, the hollow outer sealing screw 24-1, the hollow inner sealing screw 24-2 and the sealant 47, resealing is not needed when the sensor and the pipeline are replaced, and the assembly and sealing of the system are facilitated.
Further, as shown in FIGS. 2 and 5, the upper and lower thermostatic plates 17 and 18 are each composed of a cylindrical steel plate, and a portion of the top cooling liquid circulating pipe 26-2 entering the pressure chamber 8 passes through the inside of the force transmission shaft 43; the side surfaces of the upper constant temperature board 17 and the lower constant temperature board 18 are provided with grooves, and the rubber film 15, the upper constant temperature board 17 and the lower constant temperature board 18 are tightly attached by the grooves on the upper constant temperature board 17 and the lower constant temperature board 18 through the tightening rubber sleeve 34, so that the partial falling of the soil body 16 and the invasion of the gas in the pressure chamber 8 into the soil body 16 during the test are prevented.
In the embodiment of the invention, the top cooling liquid circulating pipe 26-2 is divided into six sections, wherein two sections are connected with the top thermostatic bath, two sections penetrate through the interior of the force transmission shaft 43, two sections are positioned on the upper thermostatic plate 17 and are communicated with the closed cavity 17-3 of the upper thermostatic plate 17, and six sections of the cooling liquid circulating pipe 26-2 are communicated through a prefabricated connector.
As shown in FIG. 5, the top thermostatic plate 17 comprises a lower bearing plate 17-1, a sealing rubber ring 36-5 and an upper bearing plate 17-2 which are fixed in sequence, a closed cavity 13 is formed between the lower bearing plate 17-1 and the upper bearing plate 17-2, and a load strut 17-4 is arranged between the lower bearing plate 17-1 and the upper bearing plate 17-2 for transmitting load.
Further, as shown in FIG. 6, a copper coil 18-1 is disposed in the lower thermostatic plate 18, the copper coil 18-1 is communicated with a bottom cooling liquid circulating pipe 26-1, and a channel for fixing a water inlet pipe 25, a water outlet pipe 27, the bottom cooling liquid circulating pipe 26-1 and an inner sealing screw 24-2 is disposed on the lower thermostatic plate 18.
Further, as shown in fig. 2 and 9, 4 gas pressure sensors 7, 4 laser distance measuring sensors 9, 4 soil pressure cells 10, 4 pore water pressure sensors 12 and 4 water salt sensors 13 are respectively arranged on the same vertical line at vertical intervals of 20cm, and the 4 gas pressure sensors 7 are respectively arranged in the first vacuum chamber 4, the second vacuum chamber 5, the third vacuum chamber 6 and the pressure chamber 8.
In the embodiment of the invention, the gas pressure sensor 7, the laser ranging sensor 9, the soil pressure cell 10, the pore water pressure sensor 12 and the water salt sensor 13 are internally provided with the temperature sensors, so that the step of independently burying the temperature sensors in the soil body 16 is omitted while the data function of the temperature correction sensors is achieved, the time is saved, and the test efficiency is improved.
Further, the number of the gas pressure sensors 7, the number of the laser ranging sensors 9, the number of the soil pressure cell 10, the number of the pore water pressure sensors 12 and the number of the water salt sensors 13 are 4, the number of the laser ranging sensors 9, the number of the soil pressure cell 10, the number of the pore water pressure sensors 12 and the number of the water salt sensors 13 are respectively arranged on the same vertical line, the vertical interval is 20cm, and the number of the 4 gas pressure sensors 7 are respectively arranged in the first vacuum chamber 4, the second vacuum chamber 5, the third vacuum chamber 6 and the pressure chamber 8.
Further, the bottom of the load sensor 20 is in contact with the top surface of the force transmission shaft 43 of the pressure chamber 8, and a force transmission steel plate 39 is arranged between the force transmission shaft 43 and the upper thermostatic plate 17.
Further, the axial load loading device for the soil mass 16 in the loading system 200 further comprises a limiting device for positioning the force transmission shaft 43, a limiting hole is arranged on the force transmission shaft 43, the limiting device comprises a limiting screw 56-2, a combined nut 56-3 and a screwing screw 56-4, the limiting screw 56-2 is vertically fixed at the bottom of the third reaction plate 37-3 through a thread, the combined nut 56-3 is sleeved on the limiting screw 56-2 and controls the lifting of the position of the limiting screw through the rotation of the thread, the bottom of the combined nut 56-3 is a nut with a horizontal channel, the nut with the horizontal channel can freely rotate in the horizontal direction, the screwing screw 56-4 can freely screw on the nut with the horizontal channel at the bottom of the combined nut 56-3 until the screwing screw is in contact with the limiting hole prefabricated on the force transmission shaft 43, the purpose of limiting the position of the force transmission shaft 43 is achieved.
The soil body 16 forming method of the forming system based on the large-scale soil body water-heat-force-salt four-field coupling effect test system provided by the embodiment comprises the following steps:
s1, placing the lower constant temperature plate 18 and the permeable stones 22-1-22-2 on the second reaction plate 37-2.
And S2, connecting the data transmission line connector 44 penetrating out of the inner sealing screw 24-2 through a sensor data transmission line in the prepared soil body 16.
S3, fixing the first forming protective barrel 53-1 and the rubber film 15 by the high-strength screw 2-3 and the nut 55-2 through the screw positioning slot 52 on the flange 51 and the screw fixing hole 54 on the second reaction plate 37-2; the length of the rubber film 15 is 120cm, the excess length of the rubber film 15 is rolled and sleeved outside the first forming protection barrel 53-1, and the rubber film 15 is tightly attached to the first forming protection barrel 52-1 by using the air suction holes 49 and air suction equipment.
S4, after the powder fine sand layer 23 with the thickness of 5cm is additionally arranged, the designed soil is compacted in a layered mode, and the related sensors are buried at the designed height.
S5, after the compaction height of the first forming protection barrel 53-1 is finished, releasing the length of the rolled rubber film 15 to the second forming protection barrel 53-2, additionally installing the second forming protection barrel 53-2, sleeving the excess length of the rubber film 15 outside the second forming protection barrel 53-2, and enabling the rubber film 15 to be tightly attached to the second forming protection barrel 53-2 by utilizing the air suction hole 49 and air suction equipment; and (4) adding soil, compacting in layers and burying a sensor.
S6, after the compacting height of the second forming protection barrel 53-2 is finished, releasing all the lengths of the rolled rubber film 15, installing a third forming protection barrel 53-3, enabling the rubber film 15 to be tightly attached to the third forming protection barrel 53-3 by utilizing the air suction hole 49 and air suction equipment, installing soil, continuously compacting in a layering mode and embedding a sensor until the compacting height is 10cm away from the top of the third forming protection barrel 53-3, and installing the upper constant temperature plate 17, so that the compacting forming of the soil body 16 is finished.
S7, after compaction and forming of the soil body 16 are completed, the nut 55-2, the flange 51, the high-strength screw 2-3, the first forming protection barrel 53-1, the second forming protection barrel 53-2 and the third forming protection barrel 53-3 are successively dismounted.
S8, the rubber film 15 is tightly attached to the upper thermostatic plate 17 and the lower thermostatic plate 18 by tightening the rubber sleeve 34.
The embodiment does not describe the assembly process of the water-heat-force-salt four-field coupling effect test system in the large-scale soil freezing and thawing process, which is easy to understand.
The invention provides a test method of soil mass water-heat-force-salt four-field coupling effect of a large-scale soil mass water-heat-force-salt four-field coupling effect test system, which is characterized by comprising the following steps of:
step 1, starting a data acquisition and control system, starting to acquire temperature, water salt, stress and pore water pressure information in a soil body 16, acquiring lateral and vertical deformation information of the soil body 16, acquiring gas pressure information in a first vacuum chamber 4, a second vacuum chamber 5 and a third vacuum chamber 6, and acquiring loading and unloading information of a hydraulic jack 19 on the soil body 16.
And 2, keeping the water inlet pipe 25, the water outlet pipe 27 and the scale glass tube 29 smooth, starting a loading system, setting working parameters of a servo control table through a workstation, enabling the hydraulic jack 19 to work until the force transmission shaft 43 is in contact with the force transmission steel plate 39, adjusting the air supply pressure of the air compression station to enable the air pressure in the pressure chamber 8 to reach a design value, setting the working parameters of the servo control table through the workstation again, and enabling the hydraulic jack 19 to perform constant-load consolidation on the soil body 16 until the consolidation of the soil body 16 is stable.
And 3, after the consolidation of the soil body 16 is completed, fixing the force transmission shaft 43 through a limiting device for positioning the force transmission shaft 43 to limit the displacement of the force transmission shaft, so that the rigid constraint of frost heaving of the soil body 16 is realized.
And 4, opening a vacuum pumping pump, and pumping the first vacuum chamber 4, the second vacuum chamber 5 and the third vacuum chamber 6 into a vacuum state through the vacuum pumping action, wherein the vacuum state takes the data of the gas pressure sensor 7 as a judgment basis.
And 5, opening the bottom constant temperature bath, setting the working temperatures of the bottom low-temperature constant temperature bath and the constant temperature tank 32 according to the groundwater supply temperature to be simulated, starting an external circulating pump of the bottom constant temperature bath after the bottom constant temperature bath reaches the working temperature, and heating or cooling the saline water in the Mariotte bottle 30 through the bottom cooling liquid circulating pipe 26-1 and the constant temperature tank 32 until the control panel 33 displays that the temperature of the temperature probe 31-1 reaches the design value and is stable.
Note: when the water replenishing temperature of the water replenishing system is adjusted, the function of an external circulating pump of the bottom thermostatic bath is applied, and because the bottom thermostatic bath, the bottom cooling liquid circulating pipe 26-1 and the lower thermostatic plate 18 form a closed circulating system, the working temperature of the lower thermostatic plate 18 is also set in this step, and the set working temperature of the lower thermostatic plate 18 is the same as the water supply temperature of the mahalanobis bottle 30.
Step 6, opening a water stop clamp on the water inlet pipe 25 to supply water, enabling salt-containing water in the Martin bottle 30 to enter the fine sand layer 23, and discharging gas from a graduated glass pipe 29 communicated with the fine sand layer 23; when the gas is completely exhausted, the position of the Mariotte bottle 30 is adjusted, so that the bottom of the glass tube 30-1 in the Mariotte bottle 30 and the top of the fine sand layer 23 are on the same horizontal plane, and the soil body 16 is replenished by simulating a constant underground water level.
Note: the simulated groundwater head recharge height at this time corresponds to the height of the liquid level in the ma-bottle 30 from the bottom of the glass tube 30-1 when the water stop clamp is opened.
And 7, starting the top constant temperature tank, starting an external circulating pump of the top constant temperature tank when the working temperature reaches a design value, circulating a low-temperature medium in the top constant temperature tank through the top cooling liquid circulating pipe 26-2 and the upper constant temperature plate 17, freezing the soil body 16, and finishing freezing after the temperature, water salt, stress, pore water pressure and lateral deformation of the soil body 16 are stable.
And 8, adjusting the working temperature of the top thermostatic bath, setting the working temperature of the top thermostatic bath according to the temperature for melting the soil body 16 according to the design requirement, starting an external circulating pump of the top thermostatic bath when the working temperature reaches the design value, enabling a low-temperature medium in the top thermostatic bath to pass through the top cooling liquid circulating pipe 26-2, circulating the upper thermostatic plate 17, melting the soil body 16, and finishing the melting test after the temperature, water salt, stress, pore water pressure and lateral deformation of the soil body in the soil body 16 are stable.
And 9, repeating the step 7 and the step 8 if a freeze-thaw cycle test of the soil body 16 is carried out.
And step 10, the data acquisition and control system acquires and stores the temperature, water salt, stress, pore water pressure and lateral and vertical deformation information of the soil body 16 in real time, and data processing software of the workstation analyzes and images the acquired data to obtain the dynamic coupling action of water-heat-force-salt in the freezing and thawing process of the large-scale soil body.
The large-scale soil water-heat-force-salt four-field coupling effect test system and method provided by the invention have the beneficial effects that: (1) the forming system can be used for compacting and forming large-scale soil (with the diameter of 50cm and the height of 100), the requirements on the size and the spacing of the embedded sensors are met, and the accuracy of monitoring data is guaranteed; (2) the invention can simulate the supply of the constant-temperature constant-water-head groundwater with different salinity to the soil body, and is used for researching the water-salt migration rule of the large-scale soil body under the four-field coupling action; (3) the vacuum chamber is designed to serve as a heat insulation boundary between the pressure chamber and the test environment, so that the influence of the test environment temperature on the test data side is effectively reduced; (4) the pressure chamber is designed to be used as a confining pressure providing device of the soil body, and the heat conductivity of the gas in the pressure chamber is poor, so that the formation of a temperature gradient in the freeze thawing process of the soil body is facilitated; (5) the combined application of the temperature control system, the loading system and the water supply system more truly simulates freeze thawing, stress and underground water supply environment of foundation or roadbed soil bodies in the region of frozen salinized soil in season, and provides a water-heat-force-salt coupling effect test system which is more in line with the actual situation; (6) the system can obtain the information of vertical integral deformation, lateral deformation, water and salt content distribution, pressure distribution, temperature distribution and pore water pressure distribution in the soil body in real time, and provides technical guarantee for the research of water-heat-force-salt four-field coupling effect of the large-scale soil body; (7) through the combined application of the workstation, the data acquisition box and the sensor group, the automatic acquisition and processing of test data are realized, and the reliability of data acquisition is effectively ensured.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. Large-scale soil body water-heat-power-salt four-field coupling effect test system, its characterized in that includes: the system comprises a loading frame (100), a loading system (200), a water supplementing system (300), a temperature control system (400), a data acquisition and control system (500) and a forming system (600); the loading frame (100) comprises: the device comprises a support column (42), a first reaction plate (37-1), a second reaction plate (37-2), a third reaction plate (37-3), a first high-strength screw rod (2-1) and a second high-strength screw rod (2-2); at least one first high-strength screw rod (2-1) is arranged between the second reaction plate (37-2) and the third reaction plate (37-3), the third reaction plate (37-3) is positioned above the second reaction plate (37-2), the bottom surface of the second reaction plate (37-2) is provided with at least one pillar (42), the bottom end of the second high-strength screw rod (2-2) penetrates through the second reaction plate (37-2), the position close to the bottom end is fixed on the second reaction plate (37-2) by a first sealing nut, the top end of the second high-strength screw rod (2-2) penetrates through the first reaction plate (37-1), the position close to the top end is fixed on the first reaction plate (37-1) by a second sealing nut, and the first reaction plate (37-1) is positioned above the second reaction plate (37-2), and is located below the third reaction plate (37-3);
the loading system (200) comprises: axial load loading equipment of the soil body (16) and lateral confining pressure loading equipment of the soil body (16); the axial load loading equipment of the soil body (16) comprises a hydraulic jack (19) arranged on the bottom surface of the third reaction plate (37-3) and a load sensor (20) arranged on the bottom surface of the hydraulic jack (19); the axial load loading equipment of the soil body (16) further comprises a servo control console arranged outside the loading frame, the servo control console is respectively connected with the hydraulic jack (19) and the load sensor (20) through electric connection lines, and the servo control console is used for controlling the hydraulic jack (19) to load and unload the soil body (16) or maintain constant pressure, and collecting and outputting monitoring load of the load sensor (20); the lateral confining pressure loading equipment for the soil body (16) comprises a pressure chamber (8) for sealing the soil body (16) in a gas pressure space, and a gas supply pipe (35) which penetrates through a second reaction plate (37-2) and is communicated with the pressure chamber (8), wherein one end of the gas supply pipe (35) is communicated with the pressure chamber (8), the other end of the gas supply pipe is communicated with an air compression station, and the air compression station is used for providing lateral confining pressure for the soil body (16); the pressure chamber (8) comprises a first reaction plate (37-1) bottom surface and a second reaction plate (37-2) top surface, and also comprises a first steel barrel (38-1) arranged between the first reaction plate (37-1) bottom surface and the second reaction plate (37-2) top surface; a first sealing piston sleeve (40-1) is arranged in the middle of the first reaction plate (37-1), and a force transmission shaft (43) is arranged in the center of the first sealing piston sleeve (40-1);
the hydration system (300) comprises: a Mariotte bottle (30), a water inlet pipe (25), a first permeable stone (22-1), a second permeable stone (22-2), a water outlet pipe (27) and a first glass pipe (29); the first permeable stone (22-1) and the second permeable stone (22-2) are respectively arranged at the bottom of the soil body (16), the first permeable stone (22-1) and the second permeable stone (22-2) are arranged on the same horizontal plane, two ends of the water inlet pipe (25) are respectively communicated with a water outlet of the Mariotte bottle (30) and the first permeable stone (22-1), and two ends of the water outlet pipe (27) are respectively communicated with the second permeable stone (22-2) and the first glass tube (29); the March's bottle (30) is composed of a second glass tube (30-1), a bottle body and a rubber plug (30-2), the rubber plug (30-2) plugs the bottle body, and the glass tube (30-1) penetrates through the rubber plug (30-2) to communicate the inner space and the outer space of the March's bottle (30);
the temperature control system (400) comprises: a temperature supply device and a temperature preservation device; the temperature supply equipment comprises a lower constant temperature plate (18) which is in contact with the bottom surfaces of a first permeable stone (22-1) and a first permeable stone (22-2), a bottom cooling liquid circulating pipe (26-1) communicated with the lower constant temperature plate (18), and a bottom constant temperature groove communicated with the bottom cooling liquid circulating pipe (26-1), wherein the lower constant temperature plate (18), the bottom cooling liquid circulating pipe (26-1) and the bottom constant temperature groove form a closed circulating system; the temperature control system also comprises an upper constant temperature plate (17) arranged on the top surface of the soil body (16), a top cooling liquid circulating pipe (26-2) communicated with the upper constant temperature plate (17), and a top constant temperature groove communicated with the top cooling liquid circulating pipe (26-2), wherein the upper constant temperature plate (17), the top cooling liquid circulating pipe (26-2) and the top constant temperature groove form a closed circulating system; the purpose of applying different temperature gradients to the soil body (16) is realized by setting different working temperatures for the bottom thermostatic bath and the top thermostatic bath; the temperature supply equipment further comprises a constant temperature box (32), a first temperature probe (31-2) and a second temperature probe (31-1), the Mariotte bottle (30) is arranged in the constant temperature box (32), a bottom cooling liquid circulating pipe (26-1) is wound on the bottle body, and a control panel (33) and the first temperature probe (31-1) are arranged on the constant temperature box (32); the working temperature of a thermostat (32) is monitored by a first temperature probe (31-2), the working temperature of the thermostat (32) and the working temperature of the bottom thermostatic bath are set to be the same, and a second temperature probe (31-1) is arranged in a Mariotte bottle (30);
the heat preservation device comprises: comprises a first vacuum chamber (4) positioned at the upper part of a pressure chamber (8), a second vacuum chamber (5) positioned at the lower part of the pressure chamber (8), and a third vacuum chamber (6) positioned at the side surface of the pressure chamber (8);
the first vacuum chamber (4), the second vacuum chamber (5) and the third vacuum chamber (6) are communicated through a plurality of communicating pipes (14), the first vacuum chamber (4) is communicated with a vacuumizing pipe (28), the vacuumizing pipe (28) is communicated with the vacuumizing pump, and vacuum environments of the first vacuum chamber (4), the second vacuum chamber (5) and the third vacuum chamber (6) are manufactured by switching on the vacuumizing pump;
the data acquisition and control system (500) comprises: the system comprises a sensor group, a data acquisition box and a workstation; the sensor group comprises a displacement meter (21) for monitoring the integral deformation of the soil body (16), a laser ranging sensor (9) for monitoring the lateral deformation of the soil body (16), a water salt sensor (13) for monitoring the moisture and salt content of the soil body (16), a pore water pressure sensor (12) for monitoring the pore water pressure of the soil body (16), a soil pressure box (10) for monitoring the vertical stress field change of the soil body (16), and a gas pressure sensor (7) for monitoring the gas pressure in a pressure chamber (8), a first vacuum chamber (4), a second vacuum chamber (5) and a third vacuum chamber (6); the data acquisition box is used for acquiring data monitored by the sensor group, the workstation is used for analyzing and processing the acquired data, and the workstation comprises a microcomputer and data processing software;
the forming system (600) comprises: a first forming protective barrel (53-1) arranged on a second reaction plate (37-2), a second forming protective barrel (53-2) arranged on the upper part of the first forming protective barrel (53-1), a third forming protective barrel (53-3) arranged on the upper part of the second forming protective barrel (53-2), wherein the inner walls of the first forming protective barrel (53-1), the second forming protective barrel (53-2) and the third forming protective barrel (53-3) are tightly attached with rubber membranes (15), the outer walls are respectively provided with a flange (51), the flange (51) is provided with a screw fixing groove (52), the second reaction plate (37-2) is provided with a screw fixing hole (54), and a third high-strength screw (2-3) sequentially passes through the screw fixing hole (54) on the second reaction plate (37-2), a screw fixing groove (52) on the flange (51) realizes the fixation of the first forming protection barrel (53-1), the second forming protection barrel (53-2) and the third forming protection barrel (53-3); each screw fixing groove (52) and each high-strength screw (2-3) are fixed through a first nut (55-2), and the forming system (600) further comprises compaction equipment for compacting designed soil to form a soil body (16) and a tightening rubber sleeve (34) on the side face of the rubber film (15).
2. The large-scale soil mass water-heat-force-salt four-field coupling effect test system as claimed in claim 1, wherein a second sealing rubber ring (36-3) and a supporting screw (3) are uniformly arranged between the first steel cover (41-1) and the first reaction plate (37-1) and between the second reaction plate (37-2) and the second steel cover (41-2), and the supporting screw (3) is a high-strength steel screw with threads;
the second reaction plate (37-2) and the first high-strength screw (2-1) as well as the third reaction plate (37-3) and the first high-strength screw (2-1) are fixed through a second nut (55-1);
third sealing rubber rings (36-1) are uniformly arranged between the first reaction plate (37-1) and the first steel barrel (38-1), between the first reaction plate (37-1) and the second steel barrel (38-2), between the second reaction plate (37-2) and the first steel barrel (38-1) and between the second reaction plate (37-2) and the second steel barrel (38-2);
and fourth sealing rubber rings (36-2) are uniformly arranged between the first sealing nut and the second reaction plate (37-2), between the second sealing nut and the first reaction plate (37-1), between the third sealing nut and the first steel cover (41-1) and between the fourth sealing nut and the second steel cover (41-2).
3. The large-scale soil mass water-heat-force-salt four-field coupling effect test system as claimed in claim 2, wherein the second steel cover (41-2), the second reaction plate (37-2) and the lower thermostatic plate (18) are all provided with threaded through holes matched with the sealing screw rods (24), the sealing screw rods (24) are hollow screw rods and are used for data transmission lines, bottom cooling liquid circulating pipes (26-1), water inlet pipes (25) and water outlet pipes (27) to pass through;
and a water stop clamp for controlling the flow of the Mariotte bottle (30) is arranged on the water inlet pipe (25), and a fine sand layer (23) is coated on the first permeable stone (22-1) and the second permeable stone (22-2).
4. The large scale soil mass water-heat-force-salt four-field coupling effect test system of claim 1, wherein the soil mass (16) is a cylindrical soil mass with a diameter of 50cm and a height of 100 cm; the first reaction plate (37-1), the second reaction plate (37-2) and the third reaction plate (37-3) are cylindrical steel plates;
the first forming protection barrel (53-1), the second forming protection barrel (53-2) and the third forming protection barrel (53-3) are formed by splicing two half-moon-shaped steel barrels, so that the first forming protection barrel (53-1), the second forming protection barrel (53-2) and the third forming protection barrel (53-3) are easy to remove after a soil body (16) is manufactured; the side walls of the first forming protection barrel (53-1), the second forming protection barrel (53-2) and the third forming protection barrel (53-3) are provided with air suction holes (49).
5. The large-scale soil mass water-heat-force-salt four-field coupling effect test system according to claim 1, wherein the upper constant temperature plate (17) and the lower constant temperature plate (18) are both composed of cylindrical steel plates, and a part of the top cooling liquid circulating pipe (26-2) entering the pressure chamber (8) passes through the inside of the force transmission shaft (43); go up thermostatic plate (17) and all be provided with the recess with lower thermostatic plate (18) side, through tighten rubber sleeve (34), go up thermostatic plate (17) and the recess on lower thermostatic plate (18) with rubber membrane (15), go up thermostatic plate (17) and closely laminate with lower thermostatic plate (18), prevent that the part of soil body (16) drops and the gas in pressure chamber (8) from invading soil body (16) during the test.
6. The large-scale soil mass water-heat-force-salt four-field coupling effect test system according to claim 1, wherein the number of the gas pressure sensors (7), the number of the laser ranging sensors (9), the number of the soil pressure boxes (10), the number of the pore water pressure sensors (12) and the number of the water salt sensors (13) are 4, the number of the laser ranging sensors (9), the number of the soil pressure boxes (10) and the number of the pore water pressure sensors (12) are respectively arranged on the same vertical line, the vertical interval is 20cm, and the number of the 4 gas pressure sensors (7) are respectively arranged in the first vacuum chamber (4), the second vacuum chamber (5), the third vacuum chamber (6) and the pressure chamber (8); the first vacuum chamber (4) comprises a top surface of a first reaction plate (37-1), a first sealing piston sleeve (40-1) which is arranged in the center of the first reaction plate (37-1) and is in fit contact with the first reaction plate (37-1) and a force transmission shaft (43), a first steel cover (41-1) which is arranged on the upper part of the top surface of the first reaction plate (37-1), a second sealing piston sleeve (40-2) which is arranged in the center of the first steel cover (41-1) and is in fit contact with the steel cover (41-1) and the force transmission shaft (43), a first sealing rubber ring (36-4) which is arranged between the first sealing piston (40-1) and the second sealing piston sleeve (40-2), and the top end of a second high-strength screw rod (2-2) penetrates through the first steel cover (41-1) and is fixed on the first steel cover (41-1) by a third sealing nut;
the second vacuum chamber (5) comprises a second reaction plate (37-2) bottom surface, a second steel cover (41-2) arranged at the lower part of the second reaction plate (37-2) bottom surface, and a sealing screw rod (24) arranged at the center of the second reaction plate (37-2) and the second steel cover (41-2), wherein the sealing screw rod (24) is in fit contact with the second reaction plate (37-2) and the second steel cover (41-2), and the contact part is air-tight and water-tight; the bottom end of the second high-strength screw rod (2-2) penetrates through the second steel cover (41-2) and is fixed on the second steel cover (41-2) by a fourth sealing nut;
the first steel barrel (38-1) is sleeved in the second steel barrel (38-2), and an interval formed by the outer wall of the first steel barrel (38-1) and the inner wall of the second steel barrel (38-2) is the third vacuum chamber (6).
7. The large-scale soil mass water-heat-force-salt four-field coupling effect test system according to claim 1 or 6, characterized in that the gas pressure sensor (7), the laser ranging sensor (9), the soil pressure cell (10) and the pore water pressure sensor (12) are arranged, and the temperature sensor is arranged in the water salt sensor (13) to play a role of correcting the data of the temperature sensor and simultaneously save the step of separately burying the temperature sensor in the soil mass (16).
8. The large-scale soil mass water-heat-force-salt four-field coupling effect test system according to claim 1, wherein the Mariotte bottle (30) is used for carrying pure water or water with different salinity, the bottom of the load sensor (20) is in contact with the top surface of a force transmission shaft (43) of the pressure chamber (8), and a force transmission steel plate (39) is arranged between the force transmission shaft (43) and the upper constant temperature plate (17).
9. The large-scale soil mass water-heat-force-salt four-field coupling effect test system as claimed in claim 1 or 8, wherein the axial load loading device of the soil mass (16) in the loading system (200) further comprises a limiting device for positioning the force transmission shaft (43), a limiting hole is arranged on the force transmission shaft (43), the limiting device comprises a limiting screw rod (56-2), a combined nut (56-3) and a screw-in screw rod (56-4), the limiting screw rod (56-2) is vertically fixed at the bottom of the third reaction plate (37-3) through threads, the combined nut (56-3) is sleeved on the limiting screw rod (56-2) and is controlled to ascend and descend through rotation of the threads, the bottom of the combined nut (56-3) is a nut with a horizontal channel, the nut with the horizontal channel can freely rotate in the horizontal direction, and the screw-in screw rod (56-4) can freely screw in the nut with the horizontal channel at the bottom of the combined nut (56-3) until the nut is matched and contacted with a limit hole prefabricated on the force transmission shaft (43).
10. A soil mass water-heat-force-salt four-field coupling effect test method based on the large-scale soil mass water-heat-force-salt four-field coupling effect test system in claim 1 is characterized by comprising the following steps:
step 1, starting a data acquisition and control system, starting to acquire temperature, water salt, stress and pore water pressure information in a soil body, acquiring lateral and vertical deformation information of the soil body, acquiring gas pressure information in a first vacuum chamber, a second vacuum chamber and a third vacuum chamber, and acquiring loading and unloading information of a hydraulic jack on the soil body;
step 2, keeping the water inlet pipe, the water outlet pipe and the glass pipe unblocked, starting a loading system, setting working parameters of a servo control table through a workstation, enabling the hydraulic jack to work until a force transmission shaft is contacted with a force transmission steel plate, adjusting the air supply pressure of an air compression station to enable the air pressure in a pressure chamber to reach a design value, setting the working parameters of the servo control table through the workstation again, and enabling the hydraulic jack to perform constant-load consolidation on a soil body until the consolidation of the soil body is stable;
step 3, after the consolidation of the soil body is completed, fixing the force transmission shaft through a limiting device for positioning the force transmission shaft, and limiting the displacement of the force transmission shaft, so that the rigid constraint of frost heaving of the soil body is realized;
step 4, opening a vacuum pump, and pumping the first vacuum chamber, the second vacuum chamber and the third vacuum chamber into a vacuum state through the vacuum pumping function, wherein the vacuum state takes the data of the gas pressure sensor as a judgment basis;
step 5, opening the bottom thermostatic bath, setting the working temperatures of the bottom low-temperature thermostatic bath and the thermostat according to the groundwater supply temperature to be simulated, starting an external circulating pump of the bottom thermostatic bath after the bottom thermostatic bath reaches the working temperature, and heating or cooling the saline water in the Mariotte bottle through a bottom cooling liquid circulating pipe and the thermostat until the temperature of the temperature probe displayed by the control panel reaches a design value and is stable;
step 6, opening a water stop clamp on the water inlet pipe to supply water, enabling salt-containing water in the Martin bottle to enter a fine sand layer, and discharging gas from a graduated glass pipe communicated with the fine sand layer; when the gas is completely exhausted, adjusting the position of the Mariotte bottle to enable the bottom of the glass tube in the Mariotte bottle and the top of the fine sand layer to be on the same horizontal plane, and simulating a constant underground water level to supply a soil body;
step 7, starting the top thermostatic bath, starting an external circulating pump of the top thermostatic bath when the working temperature reaches a design value, enabling a low-temperature medium in the top thermostatic bath to pass through a top cooling liquid circulating pipe and circulate through an upper thermostatic plate to freeze a soil body, and finishing freezing after the temperature, water salt and stress in the soil body, the pore water pressure and the lateral deformation of the soil body are stable;
step 8, adjusting the working temperature of the top thermostatic bath, setting the working temperature of the top thermostatic bath according to the temperature for melting the soil body according to the design requirement, starting an external circulating pump of the top thermostatic bath when the working temperature reaches a design value, enabling a low-temperature medium in the top thermostatic bath to circulate through a top cooling liquid circulating pipe and an upper thermostatic plate, melting the soil body, and finishing a melting test after the temperature, water salt, stress, pore water pressure and lateral deformation of the soil body in the soil body are stable;
9, if the freeze-thaw cycle test of the soil body is carried out, repeating the 7 th step and the 8 th step;
and step 10, acquiring and storing the temperature, water salt, stress, pore water pressure and lateral and vertical deformation information of the soil body in real time by a data acquisition and control system, and analyzing and imaging the acquired data by data processing software of a workstation to obtain the dynamic coupling action of water-heat-force-salt in the freezing and thawing process of the large-scale soil body.
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