CN111474063A - Cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing method and device - Google Patents

Cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing method and device Download PDF

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CN111474063A
CN111474063A CN202010342172.2A CN202010342172A CN111474063A CN 111474063 A CN111474063 A CN 111474063A CN 202010342172 A CN202010342172 A CN 202010342172A CN 111474063 A CN111474063 A CN 111474063A
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辛全明
曹洋
张丙吉
佘小康
尹志伟
赵晨
梁海
季铁军
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Zhongjian Dongshe Rock And Soil Engineering Co ltd
China Northeast Architectural Design and Research Institute Co Ltd
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Zhongjian Dongshe Rock And Soil Engineering Co ltd
China Northeast Architectural Design and Research Institute Co Ltd
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    • G—PHYSICS
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    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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    • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/60—Investigating resistance of materials, e.g. refractory materials, to rapid heat changes
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    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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    • G01N2203/02—Details not specific for a particular testing method
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Abstract

A method and a device for testing the water-heat-force coupling soil pressure of a multidirectional stress field of a cold region soil body are disclosed, and a horizontal and vertical loading system is arranged on a test platform. The horizontal dowel bar pushes and pulls the pushing plate. The propulsion plate compression equivalent restraint module pushes the cold ends of the loading frame and the heat exchange module, a lateral restraint plate is arranged at the cold and warm ends of the test sample and the warm ends of the cold ends in front of the cold ends, and a cover plate is arranged on the test sample. There are also a water replenishment system and a camera system. And placing the test sample on a test platform for horizontal and vertical loading, and loading the temperature to the air temperature stabilized at the depth of the simulated foundation pit to obtain test data. And a horizontal axial force acquisition sensor, a horizontal displacement sensor, a vertical load sensor, a vertical displacement sensor and a temperature and soil pressure sensor are used for acquiring data. The method can realize the research on the frost heaving coupling characteristics of the water-containing (particularly water-rich) soil body frost heaving under certain stress conditions and constraint conditions in the cold region and has important significance for researching the distribution of the frost heaving force and the development rule of the frost heaving force of the overwintering deep foundation pit.

Description

Cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing method and device
Technical Field
The invention belongs to the field of geotechnical engineering branch frozen soil engineering, and particularly relates to a method and a device for testing water-heat-force coupling soil pressure in a multidirectional stress field of a soil body in a cold region, which are suitable for testing water-heat-force coupling research under the condition of the multidirectional stress field of the soil body.
Background
In cold areas, the temperature is continuously reduced in the deep foundation pit engineering through winter. The soil body is frozen due to the negative temperature state, and the frost heaving is particularly obvious in the environment of rich water (approaching or reaching the saturated water content). The soil body of the near-empty surface of the deep foundation pit accords with the water-rich condition, so the frost heaving of the soil body can cause great load to a foundation pit supporting structure, and the safety of deep foundation pit engineering and surrounding buildings and structures is seriously influenced. The device and the method can simulate the soil body environment condition in a natural state, realize the research on the soil body frost heaving coupling characteristics with different temperature gradients under the condition of a multidirectional stress field, explore the relation between constraint and frost heaving force, know the development rule of frost heaving in space and time, and provide reference for the subsequent evaluation of the frost heaving force of the deep foundation pit.
Disclosure of Invention
The invention aims to provide a water-heat-force coupling soil pressure testing method for a multidirectional stress field of a cold region soil body, and the invention also aims to provide a water-heat-force coupling soil pressure testing device for the multidirectional stress field of the cold region soil body, which can realize the frost heaving coupling characteristic research of water-containing (especially water-rich) soil body frost heaving under a certain stress condition and a certain constraint condition in a negative temperature environment of a cold region.
The technical scheme is as follows:
the method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body is characterized by comprising the following steps of:
step 1, manufacturing a test sample, installing the test sample on a test platform, and arranging a left lateral restraint plate, a right lateral restraint plate and sensors on the left lateral restraint plate and the right lateral restraint plate.
And 2, simulating a multidirectional stress field of a deep foundation pit soil body, and carrying out vertical loading, horizontal loading and consolidation on the test sample.
And 3, carrying out temperature loading on the test sample, and simulating a temperature field and a temperature gradient in a soil body of the test sample according to the actual engineering condition.
And 4, simulating the deformation rigidity of the deep foundation pit supporting structure in the actual engineering through the equivalent constraint module. The equivalent stiffness value needs to be calculated according to the actual situation of the deep foundation pit supporting structure.
And 5, recording the water supplement amount of the test sample in the test process. And after the test is finished, the change condition of the water content of the test sample is tested before and after the test sample is subjected to slice analysis test.
And 6, testing through multiple groups of different temperature gradients to obtain the overall frost heaving development characteristics and distribution rules of the deep foundation pit in time and space.
The left lateral restraint plate and the right lateral restraint plate on the periphery of the test sample are both smeared with lubricant to reduce the side friction resistance of the test sample in the frost heaving process, and meanwhile, the cold end of the heat exchange module and the warm end of the heat exchange module are arranged at the rear end and the front end of the test sample to be attached tightly so as to limit the displacement of the warm end of the heat exchange module.
Vertical loading final value in vertical loading: n is a radical ofVertical＝ρpj·g·H·a·L(1)。
Where ρ ispjTo simulate the average density of all soil layers above the site.
g is the acceleration of gravity.
H is the depth of the simulated location.
a is the horizontal plane side length of the test specimen, and L is the longitudinal side length of the test specimen.
The conversion can obtain that the vertical direction of the test sample reaches sigma1Initial stress state:
σ1＝ρpj·g·H (2)。
horizontal load final value in horizontal load:
for static soil pressure conditions:
Nsp＝K0·σ1·a·b (3)。
wherein, K0＝1-sinφ。
For active soil pressure conditions:
Nsp＝(tan2(45-φ/2)·σa-2c·tan(45-φ/2))·a·b (4)。
wherein σaIs the active earth pressure at the simulated location.
Consolidation: after the test sample is placed, the loading control system realizes the synchronous equal proportion loading of the test sample in the vertical direction and the horizontal direction or the loading according to a certain path so as to realize that the stress of the test sample in the two orthogonal directions of the lateral direction and the horizontal direction reaches the target state in the initial stage,
while loading, starting a data acquisition system to acquire deformation delta of the test sample in the vertical direction and the horizontal direction1And Δ2。
The automatic loading control system automatically adjusts the loading according to the size of the soil sample or the stress change of the soil body, and keeps the position of the solidified soil sample in the horizontal loading direction unchanged.
Temperature loading: by adjusting cold end cold bath and warm end cold bath, the cold end of the heat exchange module and the warm end of the heat exchange module reach low temperature of 0-2 ℃, the whole temperature field condition of the test sample is monitored by temperature sensors distributed on two sides of the test sample, and when the whole temperature field of the test sample reaches uniform and even distribution, the cold end cold bath temperature is reduced to reduce heatAnd the purpose of the cold end of the heat exchange module is to stabilize the temperature of the cold end of the heat exchange module at the simulated ambient temperature. With the temperature reduction of the cold end of the heat exchange module, the test sample begins to gradually freeze at the cold end and generates frost heaving phenomenon due to the migration and phase change of moisture. The total frost heaviness delta is estimated before testingJelly made from plantThe frost heaving compression deformable quantity delta of the equivalent constraint module meets the following condition:
Δ≥2(Nsp/Keq-Nsp·L/(a·b·Esoil for soil)+ΔJelly made from plant) (5)。
The initial length of the equivalent constraint module (10) should satisfy the following condition:
L0≥n·dbullet+Δ (6)。
Wherein Δ is the compressible deformation of the equivalent restraint module.
NspThe values are initially loaded for the horizontally loaded system.
KeqThe rigidity of the spring hooke is equivalent converted according to a deep foundation pit supporting system.
ESoil for soilThe samples were tested for compressive modulus. a. b are the cross-sectional dimensions of the test specimens, respectively.
ΔJelly made from plantTo estimate the amount of frost heaving, L is the longitudinal length of the test specimen.
L0Is the initial length of the equivalent constraint module.
And N is the number of spiral turns of the equivalent restraint module spring. dBulletIs the diameter of the spring.
Calculation of equivalent stiffness: the test method is designed by adopting an elastic fulcrum method. The testing method can be used for evaluating the soil pressure of the side wall of the deep foundation pit in the cold region, and relates to the fact that the supporting rigidity of the deep foundation pit supporting structure is equivalent to the constraint rigidity of the testing device. The device comprehensively simulates the supporting structure constraint and the embedded end passive soil pressure of a pile body on the inner side of a foundation pit through a spring with equivalent constraint stiffness, and performs equivalent calculation by considering the parameter characteristics of the supporting structure of the deep foundation pit between the ground and the bottom of the deep foundation pit to obtain the equivalent deformation stiffness K at a certain point of the deep foundation piteq。
Keq＝KGeneral assembly/Ck(7)。
Wherein, KGeneral assemblyThe comprehensive rigidity of the passive soil pressure at the restraining and embedding ends of the foundation pit supporting structure is achieved.
CkThe spring rate similarity coefficient.
The comprehensive rigidity of the restraint of the deep foundation pit supporting structure and the passive soil pressure at the embedding end is calculated according to the following formula.
Figure BDA0002468904650000031
Wherein, α1、α2、α3、α4Adjusting coefficient for stiffness
kiAnd the deformation rigidity of the ith anchor cable is obtained.
k′iThe deformation rigidity of each steel purlin is obtained.
And n is the number of anchor cable channels.
Ks is the equivalent stiffness of the supporting pile body embedding end by the passive soil pressure.
Kp is the constraint rigidity of the supporting pile body.
Kg is the restraining stiffness of the crown beam.
Water supplement system: the water supply bottle is connected with a dropper inlet. And filter paper is arranged between the rear part of the warm end shell of the heat exchange module and the test sample. And a permeable stone is arranged below the test sample. The permeable stone is arranged in the open groove of the test platform, and a water collecting tank is arranged below the permeable stone. The water catch bowl is fixed in test platform below. Water enters the dropper from the water supply bottle by means of gravity, and filter paper is soaked at the contact position of the test sample and the warm end shell of the heat exchange module from the water supply hole. Water is continuously introduced by a drip tube through external water supply, and redundant water enters the water collecting tank through the permeable stone at the test sample end under the action of gravity.
The water supply bottle and the water collection tank are respectively provided with water volume scales, and the water volume absorbed by the soil body is calculated according to the water supply volume and the water collection volume in the test process.
And recording the water supplement amount of the test sample in the test process, and slicing the test sample after the test is finished. The change condition of the water content of the sample before and after the analysis test deeply analyzes the rule of water migration, and is convenient for verifying the numerical analysis result.
The horizontal loading system comprises a horizontal power device, a horizontal dowel bar, a horizontal axial force acquisition sensor, a horizontal displacement sensor, a directional plate, a propulsion plate, an equivalent restraint module, a horizontal guide rail, a loading frame, a heat exchange module cold end, a lateral restraint plate and a heat exchange module warm end.
The output part of the horizontal power device is connected with the rear end of the horizontal dowel bar.
The horizontal power device is fixedly arranged on the test platform.
The test platform is fixed with an orientation plate, and the horizontal dowel bar passes through a dowel bar hole in the middle of the orientation plate.
The front end of the horizontal dowel bar is fixedly connected with a propelling plate. The pushing plate is positioned in front of the orientation plate.
The pushing plate is sleeved on the horizontal guide rail through the pushing plate hole, and the horizontal guide rail penetrates through the guide rail hole of the directional plate on the directional plate.
And a horizontal shaft force acquisition sensor is arranged on the horizontal dowel bar.
The horizontal displacement sensor is positioned between the orientation plate and the propulsion plate.
The front end of the horizontal guide rail is fixedly connected with a loading frame.
The front end of the loading frame contacts with the cold end shell of the heat exchange module.
The front of the cold end of the heat exchange module is an area for placing a test sample.
And the equivalent constraint module is arranged on the horizontal guide rail and is positioned between the propulsion plate and the loading frame.
The warm end of the heat exchange module is fixedly arranged in front of the area for placing the test sample.
Vertical lateral restraint plates are fixedly arranged on the left side and the right side of the area for placing the test sample.
And a temperature sensor and a soil pressure sensor are arranged on the lateral restraint plate.
A vertical loading system: the vertical loading system comprises a reaction frame, a vertical power device, a vertical load sensor, a vertical loading rod, a cover plate and a vertical displacement sensor.
And a vertical power device is fixed below the transverse bracket of the reaction frame.
The output part of the vertical power device is connected above the vertical loading rod.
And a cover plate is fixed at the lower end of the vertical loading rod.
The vertical load sensor is positioned on the vertical loading rod.
The vertical displacement sensor is positioned above the cover plate and between the supports fixed on the test platform.
The cover plate is located in the area above where the test specimen is placed.
And a water replenishing system is arranged in the area for placing the test sample.
Water supplement system: a plurality of water supply holes are formed in the rear portion of the warm end shell of the heat exchange module, a plurality of drip pipes are arranged in the warm end shell of the heat exchange module, and outlets of the drip pipes are correspondingly connected with the water supply holes.
The water supply bottle is connected with a dropper inlet.
And filter paper is arranged between the rear part of the warm end shell of the heat exchange module and the test sample.
And a permeable stone is arranged below the test sample. The permeable stone is arranged in the slot of the test platform.
A water collecting tank is arranged below the permeable stone.
The horizontal power device is a horizontal stepping guide rail, and the rear end of the horizontal dowel bar is fixed at the output part of the horizontal stepping guide rail.
The vertical power device is a vertical loading motor and is in threaded connection with the upper part of the vertical loading rod.
The vertical loading rod is provided with a guide block, the lower part of the transverse support is provided with a guide frame, the guide frame is provided with a vertical guide groove, and the guide block is positioned in the guide groove.
The equivalent restraint module is a spring. The test platform is provided with a camera.
The advantages are that:
the device and the method provide a research device and a research idea for the research on the characteristics of the frozen soil of the overwintering deep foundation pit, the side slope and the like in the cold region, can realize the research on the frozen expansion coupling characteristics of the water-containing (particularly water-rich) soil body frozen expansion under a certain stress condition and a certain constraint condition in the cold region under the negative temperature environment, and have important significance for the research on the frozen expansion force distribution and the frozen expansion force development rule of the overwintering deep foundation pit.
Drawings
Fig. 1 is a front view of the device.
Fig. 2 is a schematic structural view of main parts in fig. 1.
Fig. 3 is a top view of the device.
Fig. 4 is a front view (left side in fig. 3) of the left lateral restraining plate.
Fig. 5 is a front view (right side in fig. 3) of the right lateral restraining plate.
Fig. 6 is a front view of the pusher plate.
Fig. 7 is a top view of the pusher plate.
Fig. 8 is a front view of the positioning plate.
Fig. 9 is a top view of the positioning plate.
Fig. 10 is a schematic structural view of the water replenishing system.
Fig. 11 is a schematic view of the structure of the water supply hole and the warm end of the heat exchange module.
Fig. 12 is a side view of a deep foundation pit.
Fig. 13 is a front view of fig. 12.
Fig. 14 is a schematic diagram of equivalent constraint stiffness of anchor cable, waist rail and support pile structures simulating a deep foundation pit.
Fig. 15 is a system block diagram.
Fig. 16 is a stress state diagram (normal temperature) of a soil sample (test specimen).
Fig. 17 is a stress state diagram (active soil pressure to static soil pressure) of a soil sample (test specimen).
Fig. 18 stress state diagram of soil sample (test specimen) (active soil pressure to static soil pressure transition and even to passive soil pressure again).
The device comprises a reaction frame 1, a transverse support 1a, a vertical support 1b, a vertical loading motor 2, a horizontal shaft force acquisition sensor 3, a cover plate 4, an upper cover plate 4a, a lower heat insulation cover plate 4b, a lateral restraint plate 5, a left lateral restraint plate 5a, a right lateral restraint plate 5b, a lateral support 6, a directional plate 7, a horizontal stepping guide rail 8, a thrust plate 9, an equivalent restraint module 10, a horizontal guide rail 11, a loading frame 12, a heat exchange module cold end 13, a heat exchange module warm end 14, a heat preservation cover 15, a temperature sensor 16, a test sample 17, a loading controller 18, a cold end cold bath 19, a warm end cold bath 20, a test platform 21, a water supplementing system 22, a horizontal displacement sensor 23, a horizontal loading motor 24, a horizontal force transmission rod 25, a lateral anchorage cable restraint plate hole groove 26, a camera 27, a force transmission rod hole 28, a directional plate guide rail hole 29, a anchor cable restraint hole 30, a supporting pile 31, a, The device comprises the ground 33, a foundation pit bottom 34, a vertical displacement sensor 35, a vertical load sensor 36, a vertical loading rod 37, a loading control system 38, a data acquisition system 39, an image shooting system 40, a temperature control system 41, a soil pressure sensor 42, a propulsion plate hole 43, a support 44, a water supply hole 45, a drip tube 46, a water supply bottle 47, filter paper 48, a permeable stone 49, a water collecting tank 50, a crown beam 51, a guide block 52, a guide frame 53, a guide groove 54, a freezing layer 55, a heat insulating layer 56 and a metal layer 57.
Detailed Description
Example 1
A cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing device is provided with a testing platform 21.
The test platform 21 is provided with a horizontal loading system and a vertical loading system.
The horizontal loading system comprises a horizontal power device (a horizontal loading motor 24 and a horizontal stepping guide rail 8), a horizontal dowel bar 25, a horizontal shaft force acquisition sensor 3, a horizontal displacement sensor 23, a horizontal guide rail 11, a directional plate 7, a propulsion plate 9, an equivalent restraint module 10, a loading frame 12, a heat exchange module cold end 13, a lateral restraint plate 5, a lateral support 6 and a heat exchange module warm end 14.
The output of the horizontal power device is connected with the rear end of the horizontal dowel bar 25.
The horizontal stepping guide rail 8 and a horizontal loading motor 24 (stepping) thereof are fixedly arranged on the test platform 21.
The rear end of the horizontal dowel bar 25 is fixed at the output part of the horizontal stepping guide rail 8.
Two orientation plates 7 arranged in front and back are fixed on the test platform 21, and the horizontal dowel bar 25 passes through a dowel bar hole 28 in the middle of the orientation plates 7.
The front end of the horizontal dowel bar 25 is fixedly connected with a pushing plate 9. The thrust plate 9 is located in front of the two orientation plates 7.
The pushing plate 9 is sleeved on the two horizontal guide rails 11 through the two pushing plate holes 43, and each horizontal guide rail 11 passes through the corresponding guide rail hole 29 of the orientation plate 7.
The horizontal dowel 25 is located between the two horizontal rails 11.
The horizontal dowel bar 25 is provided with a horizontal shaft force acquisition sensor 3 (the horizontal dowel bar 25 can be divided into a front end and a rear end in a specific installation mode, and the horizontal shaft force acquisition sensor 3 is arranged in the middle) so as to acquire the shaft force value of the horizontal dowel bar 25 at any time.
The horizontal axis force acquisition sensor 3 is located between the orientation plate 7 and the thrust plate 9 located at the front.
The horizontal displacement sensor 23 is located between the forward oriented plate 7 and the thrust plate 9, outside the horizontal guide rail 11.
Horizontal displacement sensors 23 are respectively arranged on two sides of the pushing plate 9, and the collected displacement is averaged.
The shell of the horizontal displacement sensor 23 is fixed in front of the orientation plate 7 positioned in front, and the probe of the horizontal displacement sensor 23 is connected behind the propulsion plate 9.
The front ends of the two horizontal guide rails 11 are fixedly connected with a loading frame 12.
The front end of the loading frame 12 contacts the shell of the cold end 13 of the heat exchange module.
A test specimen 17 is placed in front of the cold end 13 of the heat exchange module.
The horizontal guide rail 11 is provided with an equivalent restraint module 10, the equivalent restraint module 10 is positioned between the pushing plate 9 and the loading frame 12, and the equivalent restraint module 10 is a spring.
A warm end 14 of the heat exchange module is fixedly arranged in front of the area where the test specimen 17 is placed.
Vertical lateral restraint plates 5 are fixedly arranged on the left side and the right side of the area for placing the test sample 17.
Lateral supports 6 are arranged on the outer sides of the lateral restraint plates 5.
The warm end 14 of the heat exchange module, the lateral restraint plate 5 and the lateral support 6 are all fixed on the test platform 21.
The lateral restraint plate 5 is transversely provided with a plurality of lateral restraint plate hole grooves 26 along a horizontal center line, and the temperature sensors 16 can be inserted into the lateral restraint plate holes.
The lateral restraint plates 5 on the two sides are respectively a left lateral restraint plate 5a and a right lateral restraint plate 5b, and the lateral restraint plate hole grooves 26 (reserved holes) on the upper side are distributed in a staggered quincunx shape.
The lateral restraining plate 5 (left lateral restraining plate 5a) is provided with a plurality of lateral restraining plate pressure sensor holes in the horizontal direction, and soil pressure sensors 42 are provided.
The test platform 21 is also provided with a camera 27 which is positioned at the left side of the test sample 17.
The lateral restraint plate 5 and the lateral support 6 are made of transparent organic glass materials.
The heat preservation cover 15 is fixed on the test platform 21 and covers the test sample 17, the lateral restraint plate 5, the lateral support 6, the cold end 13 of the heat exchange module, the warm end 14 of the heat exchange module, the loading frame 12 and the camera 27.
The horizontal guide rail 11 and the front end of the equivalent restraint module 10 extend into the heat-insulating cover 15.
The contact surface of the cold end 13 of the heat exchange module and the loading frame 12 is covered with a nylon material to form a thermal insulation layer 56 (nylon layer) for isolating the heat exchange between the test sample 17 and the outside air.
The contact surface of the cold end 13 of the heat exchange module and the test sample 17 is a metal layer 57 (made of brass), and the brass has high heat conduction efficiency, so that the temperature of the test sample 17 can be conveniently controlled.
The front end of the test sample 17 is a warm end 14 of the heat exchange module, two sides of the test sample 17 are restrained by lateral restraining plates 5, and static soil pressure sigma is formed laterally at normal temperature2State, applying vertical load in the upper part to form sigma1Stress state, applying horizontal load at cold end 13 of heat exchange module to form sigma3Active earth pressure stress state, as shown in fig. 16.
The axis of the horizontal dowel bar 25 is coaxial with the central line of the test specimen 17 and is parallel to the axis of the horizontal guide rail 11, so that the direction is constant in the loading process.
Three holes (two guide rail holes 29 of the orientation plate and the axis of each hole of a force transmission rod hole 28 are parallel) are reserved in the middle of the orientation plate 7 and are respectively passed by the two horizontal guide rails 11 and the horizontal force transmission rod 25, the diameter of each hole is 0.5-1.0 mm larger than that of each hole of the horizontal guide rails 11 and the horizontal force transmission rod 25, and lubricating grease is coated on the horizontal guide rails 11 and the horizontal force transmission rods 25.
The pushing plate 9 is provided with two preformed holes (pushing plate holes 43), and the distance between the two holes is the same as the center distance and the hole diameter of the guide rail hole 29 of the directional plate, so that the horizontal guide rail 11 can conveniently pass through the holes. An equivalent constraint stiffness spring with the stiffness of K is arranged between the propulsion plate 9 and the loading frame 12eq。
The horizontal loading motor 24 drives the horizontal dowel bar 25 on the horizontal stepping guide rail 8 to move back and forth along the horizontal stepping guide rail 8 through screw transmission, the pushing plate 9 is pushed, the horizontal guide rail 11 slides along the directional plate 7, the equivalent restraint module 10 (spring) is compressed, and the horizontal force is loaded to the loading frame 12 and the heat exchange module 13 (cold end) through the equivalent restraint module 10 (spring) to load the test sample 17. To ensure uniform loading, the horizontal dowel bar 25, the pusher plate 9, the horizontal guide rail 11 and the loading frame 12 can only slide back and forth along three holes of the orientation plate 7.
The lateral direction of the test sample 17 is restrained by the lateral direction restraint plate 5 supported by the lateral direction support 6, so that the lateral direction of the test sample 17 is not deformed and displaced. The test specimen 17 is bounded rearwardly by the warm end 14 of the heat exchange module.
The orientation plate 7 is fixed on the test platform 21 and plays a guiding role, the horizontal guide rail 11 penetrates into the orientation plate guide rail hole 29 of the orientation plate 7, and all parts moving in the horizontal direction can only move in the direction of the orientation plate guide rail hole 29 of the orientation plate 7.
The camera 27 is correspondingly connected with the image shooting system 40, and the development rule of the freezing-frost heaving process of the test sample 17 is observed through the transparent lateral constraint plate 5.
The temperature sensor 16 and the soil pressure sensor 42 are inserted in the test specimen 17.
The equivalent constraint module 10 is a simulation component, the device simulates the deformation rigidity of a crown beam 51, an anchor cable 30, a steel support, a support pile 31 and a steel purlin or a waist beam 32 in actual engineering through the equivalent constraint module 10, and a reserved space between the loading frame 12 and the cold end 13 of the heat exchange module is convenient for connecting a refrigerant circulating pipe of the cold-end cold bath 19 with the cold end 13 of the heat exchange module.
5-8 lateral restraint plate hole grooves 26 are reserved on the central line of the long axis of each lateral restraint plate 5, two plates of a left lateral restraint plate 5a and a right lateral restraint plate 5b are crossly grooved, the axial distance of the lateral restraint plate hole grooves 26 is 1-3cm, the grooving length is 2-4cm, a temperature sensor 16 and a soil pressure sensor 42 are arranged at the contact position of the left lateral restraint plate 5a and the right lateral restraint plate 5b at two sides of a test sample 17 (soil sample), the grooving is convenient for reserving a displacement space during frost heaving, the grooving of the lateral restraint plates 5a and 5b are mutually staggered as shown in figures 4 and 5, and the grooving of the two plates are distributed in a quincunx shape.
The thickness of the lateral restraint plate 5 is 2-4cm, transparent and low-heat-conductivity materials such as an organic glass plate are adopted, and the lateral deformation of the lateral restraint plate 5 is limited by adopting a method of uniformly laterally supporting 6 (supporting plates) on two outer sides of the lateral restraint plate 5.
The horizontal loading system is covered by a heat insulation and insulation box 15, heat exchange is reduced, the temperature of the periphery of the test sample 17 is kept constant within a certain range, and the size characteristics of the cold end 13 of the heat exchange module and the warm block 14 of the heat exchange cold end are that the size in the horizontal direction is 0.5-2 mm smaller than that of the test sample 17, and the size in the vertical direction is 2-5 mm smaller than that of the test sample 17, so that the module is prevented from limiting the movement of the loading system in the solidification process in the initial stage.
The cold end 13 of the heat exchange module is correspondingly connected with a cold end cold bath 19.
The warm end 14 of the heat exchange module is connected to a corresponding warm end cooling bath 20.
A vertical loading system: the vertical loading system comprises a reaction frame 1, a vertical power device (vertical loading motor 2), a vertical load sensor 36, a vertical loading rod 37, a cover plate 4 and a vertical displacement sensor 35.
The reaction frame 1 is fixed on the test platform 21.
The reaction frame 1 is a frame structure and comprises two vertical supports 1b (positioned outside the left side and the right side of the heat-insulating cover 15) and a transverse support 1a (positioned outside the upper side of the heat-insulating cover 15) fixed on the vertical supports 1b
A vertical power device is fixed below the transverse bracket 1 a.
The output part (power shaft thread of the vertical loading motor 2) of the vertical power device is connected above the vertical loading rod 37.
The vertical loading rod 37 is provided with a guide block 52, a guide frame 53 is arranged below the transverse support 1a, the guide frame 53 is provided with a vertical guide groove 54, and the guide block 52 is positioned in the guide groove 54.
The lower end of the vertical loading rod 37 is fixed with a cover plate 4.
The cover plate 4 comprises an upper cover plate 4a (steel) and a lower heat insulation cover plate 4b (organic glass low heat conduction material to reduce temperature field interference caused by heat conduction) which are fixedly connected. The vertical load sensor 36 is located on a vertical load bar 37. The specific installation mode is as follows: the vertical load sensor 36 is located between vertical loading rods 37 divided into upper and lower ends.
The vertical loading rod 37 penetrates the heat-insulating cover 15. The vertical load sensor 36 is located within the insulated housing 15.
The vertical displacement sensor 35 is located above the cover plate 4 and between a bracket 44 fixed to the test platform 21.
The bracket 44 is located inside the heat-retaining cover 15.
The housing of the vertical displacement sensor 35 is fixedly supported by a bracket 44 fixed on the test platform 21, and the probe of the vertical displacement sensor 35 is fixed above the cover plate 4 (the upper cover plate 4 a).
The cover plate 4 is positioned in the heat-insulating cover 15 and above the test sample 17.
The reaction frame 1, the vertical loading motor 2, the vertical load sensor 36 and the vertical loading rod 37 are on the same axis and coincide with the center of the plane of the test sample 17 (test soil sample).
The lower end of the vertical loading rod 37 is hemispherical and is in contact with the hemispherical groove with the same diameter on the upper surface of the upper cover plate 4a, and the hemispherical contact area is large. The stress is more uniform. And positioning is facilitated.
The upper cover plate 4a (steel) and the lower insulating cover plate 4b have the same width as the test specimen 17.
The power shaft of the vertical loading motor 2 is in threaded connection with the upper part of the vertical loading rod 37.
The vertical loading motor 2 rotates through a power shaft, and the vertical loading rod 37 carries the cover plate 4 to move up and down under the guiding action of the guide block 52 and the guide groove 54.
And (3) a water replenishing system 22: a plurality of water supply holes 45 are formed in the rear of the shell of the warm end 14 of the heat exchange module, a plurality of drip pipes 46 are arranged in the shell of the warm end 14 of the heat exchange module, and outlets of the drip pipes 46 are correspondingly connected with the water supply holes 45.
A water supply bottle 47 is connected to the inlet of the drip tube 46.
A filter paper 48 is provided between the rear of the housing at the warm end 14 of the heat exchange module and the test specimen 17.
A permeable stone 49 is provided under the test sample 17. The permeable stone 49 is arranged in the open groove of the test platform 21, and a water collecting tank 50 is arranged below the permeable stone 49. The water collection tank 50 is fixed below the test platform 21.
Water gravity wicks the filter paper 48 from the water supply bottle 47 into the drip tube 46 and from the contact of the test specimen 17 with the housing of the warm end 14 of the heat exchange module at the water supply hole 45.
The water is continuously introduced by the drip tube 46 by external water supply, and the excess water is introduced into the water collection tank 50 through the permeable stone 49 at the lower end of the test specimen 17 by gravity.
The water replenishing system 22 is used for replenishing water for the test sample 17, only water needs to be supplied to contact with the bottom of the test sample 17, and the water is absorbed and dispersed uniformly through the capillary principle of the test sample 17.
The water supply bottle 47 and the water collection tank 50 are respectively provided with water volume scales, and the water volume absorbed by the soil body can be calculated according to the water supply volume and the water collection volume in the test process.
1. The load control system 38: the load control system 38 mainly includes the load controller 18, a vertical loading system, and a horizontal loading system. The loading controller 18 can control the loading values of the vertical loading and horizontal loading systems and automatically keep constant, while the horizontal loading system has a displacement control function (position locking).
The loading controller 18 is powered by an independent power supply and is connected to a computer through RS 232/485. The input end is connected with the data acquisition system 39, and the output end is connected with two motors of the vertical loading system and the horizontal loading system.
The loading controller 18 is mainly a P L C controller, and can preset a loading value through software, the software adjusts a motor of the loading system in a feedback mode according to data collected by the data collecting system 39, and loads or unloads the soil body of the test sample 17, so that the soil body load is constant at the preset value of the software.
The equivalent constraint module 10 calculates the deformation stiffness of the deep foundation pit supporting structure, and performs equivalent calculation to obtain the equivalent deformation stiffness E at a certain point of the foundation pit by considering the characteristics of the anchor cable 30, the support pile 31 or the waist beam 32 between the ground 33 and the bottom 34 of the foundation pit and the likeeqAs shown in fig. 12, 13, 14.
2. Temperature control system 41: the temperature control system 41 mainly includes two low-temperature constant-temperature circulating tanks as a cold-end cold bath 19 and a warm-end cold bath 20, one for controlling the temperature of the cold end 13 of the heat exchange module of the test sample 17 to control the cold-end temperature of the test sample 17, and the other for controlling the temperature of the warm end 14 of the heat exchange module to form a temperature gradient in the axial direction of the test sample 17. The left and right lateral restraint plates 5 of the test sample 17 are made of transparent organic glass, so that the heat conduction and radiation influence is effectively reduced, and the temperature fluctuation is further reduced through the heat insulation cover 15 on the outer side.
After the soil sample is solidified and the temperature working condition is started, the freezing phase change of the test sample 17 at the cold end side changes from the active soil pressure to the static soil pressure, even to the passive soil pressure, and the stress state of the test sample is changed as shown in fig. 17 and 18.
The temperature can be set by software in the temperature control system 41. The software will control the operation of the high and low temperature cycle devices based on the data from the temperature sensor 16 in the system. The refrigerant heating media are high-purity absolute alcohol and are used for temperature control equipment. The temperature control system 41 is used for refrigerating and heating temperature control equipment parts, and is a purchased finished product of equipment.
3. The data acquisition system 39: the device mainly comprises a data acquisition instrument and a plurality of sensors, wherein the data acquisition instrument comprises a static strain acquisition instrument and a temperature acquisition instrument, and the sensors comprise a horizontal axis force acquisition sensor 3, a horizontal displacement sensor 23, a soil pressure sensor 42, a vertical displacement sensor 35, a vertical load sensor 36 and a temperature sensor 16 which are all connected with the corresponding data acquisition instrument.
In the loading control system 38, the loading force is set by software. The software controls the corresponding loading motors to load or unload according to the output data of the horizontal axis force acquisition sensor 3, the horizontal displacement sensor 23, the vertical displacement sensor 35 and the vertical load sensor 36. Meanwhile, the software can acquire the displacement data of the test sample 17, and can also set the displacement data, and the corresponding loading motor (stepping and servo) is controlled by the software to be loaded to the set position. And simultaneously collecting the soil pressure.
Example 2
The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body comprises the following steps:
step 1, manufacturing a test sample, installing the test sample on a test platform, and arranging a left lateral restraint plate, a right lateral restraint plate and sensors (an earth pressure sensor 42 and a temperature sensor 16) on the left lateral restraint plate and the right lateral restraint plate.
And 2, simulating a multidirectional stress field of a deep foundation pit soil body, and carrying out vertical loading, horizontal loading and consolidation on the test sample.
And 3, carrying out temperature loading on the test sample, and simulating a temperature field and a temperature gradient in a soil body of the test sample according to the actual engineering condition.
And 4, simulating the deformation rigidity of the deep foundation pit supporting structure in the actual engineering through the equivalent constraint module. The equivalent stiffness value needs to be calculated according to the actual situation of the deep foundation pit supporting structure.
And 5, recording the water supplement amount of the test sample in the test process. And after the test is finished, the change condition of the water content of the test sample is tested before and after the test sample is subjected to slice analysis test.
And 6, testing through multiple groups of different temperature gradients to obtain the overall frost heaving development characteristics and distribution rules of the deep foundation pit in time and space.
The method specifically comprises the following steps:
before the multi-stress field coupling frost heaving test is started, a series of conventional auxiliary tests are required to be carried out, wherein the conventional auxiliary tests mainly comprise a density test, a water content test, a compaction test, a triaxial test, a consolidation test and the like so as to obtain the original density rho and the natural water content omega of a soil body1And converting the dry densityDegree rhod1Maximum dry density ρdmaxOptimum water content omegaoptEarth friction angle phi and compression modulus ESoil for soilAnd (5) waiting for parameters, and recording the depth of the soil taking position.
Crushing and drying the obtained soil sample so as to configure the target water content omega2Earth mass (omega)2May be omega1～ωSaturation of) And soaking for no less than 24h after preparation, and detecting for 3 times before sample preparation. Manufacturing target dry density rho by adopting sample preparation deviced2Test specimen No. 17 (rectangular parallelepiped soil sample), Dry Density ρd2Selectable rhod1～ρd3Range of where pd3＝(0.8～0.9)ρdmax。
After the test sample 17 is manufactured, the mold is removed, and the test sample is mounted on the test platform 21, and the left side constraining plate 5a and the right side constraining plate 5b are provided, and the soil pressure sensor 42 is provided thereon.
The left lateral restraint plate 5a and the right lateral restraint plate 5b around the test sample 17 are both coated with vaseline and other lubrication to reduce the side friction resistance of the test sample 17 in the frost heaving process, meanwhile, the cold end 13 and the warm end 14 of the heat exchange module are arranged at the rear end and the front end of the test sample 17 and are tightly attached to limit the displacement of the warm end 14 of the heat exchange module, and the values of upper vertical loading and horizontal loading are set according to the simulated position depth.
Vertical loading final value: n is a radical ofVertical＝ρpj·g·H·a·L (1)。
Where ρ ispjTo simulate the average density of all soil layers above the site.
g is the acceleration of gravity.
H is the depth of the simulated location.
a is the horizontal plane side length of the test specimen 17, and L is the longitudinal side length of the test specimen 17.
The test sample 17 can be converted to reach sigma in the vertical direction1Initial stress state:
σ1＝ρpj·g·H (2)。
horizontal loading final value:
for static soil pressure conditions:
Nsp＝K0·σ1·a·b (3)。
wherein, K0＝1-sinφ。
For active soil pressure conditions:
Nsp＝(tan2(45-φ/2)·σa-2c·tan(45-φ/2))·a·b (4)。
wherein σaIs the active earth pressure at the simulated location.
Consolidation: after the test sample 17 is placed, the loading control system 38 is used for synchronously and proportionally loading the test sample 17 in the vertical direction and the horizontal direction (axial direction) or loading the test sample 17 according to a certain path, so that the initial stress of the test sample 17 in the lateral direction and the axial direction in two orthogonal directions reaches a target state (the stress in each direction can be in an active, static or passive earth pressure state).
While loading, the data acquisition system 39 is activated to acquire the deformation Δ of the test specimen 17 in the vertical and axial directions1And Δ2(vertical displacement sensor 35 and horizontal displacement sensor 23).
The automatic loading control system 38 automatically adjusts and loads according to the size of the soil sample or the stress change of the soil body, and inserts the temperature sensor 16 into the test sample 17 along the lateral restraining plate hole grooves 26 of the two lateral restraining plates 5 after the loading is stable, and keeps the position after consolidation in the horizontal loading direction unchanged. Or the temperature sensor 16 may be inserted on the lateral restraining plate 5 together with the soil pressure sensor 42.
Temperature loading: after the temperature loading is finished, the cold ends of the cold ends 13 and the warm ends 14 of the heat exchange modules reach the low temperature of (0-2) DEG C by adjusting the cold end cold baths 19 and the warm end cold baths 20, the overall temperature field condition of the test sample 17 is monitored by the temperature sensors 16 distributed on the two sides of the test sample 17, when the overall temperature field of the test sample 17 reaches the consistent and uniform distribution, the cold ends of the heat exchange modules 13 are reduced by reducing the temperature of the cold end cold baths 19, the cooling speed is (0.5-1.5) DEG C/h, and finally the temperature of the cold ends 13 of the heat exchange modules is stabilized at the simulated environmental temperature. Followed byThe temperature at the cold end 13 of the heat exchange module decreases and the test sample 17 begins to gradually freeze at this end and freeze due to moisture migration and phase change. The total frost heaviness delta is estimated before testingJelly made from plantThe frost heaving compression deformable amount Δ of the equivalent restraint module 10 (spring) should satisfy the following condition:
Δ≥2(Nsp/Keq-Nsp·L/(a·b·Esoil for soil)+ΔJelly made from plant) (5)。
The initial length of the equivalent constraint module 10 should satisfy the following condition:
L0≥n·dbullet+Δ (6)。
Where Δ is the amount of compressible deformation of the equivalent restraint module 10 (spring).
NspThe values are initially loaded for the horizontally loaded system.
KeqThe rigidity of the spring hooke is equivalent converted according to a deep foundation pit supporting system.
ESoil for soilThe compression modulus of sample 17 (soil mass) was tested. a. b are the cross-sectional dimensions of the test specimen 17 (soil mass), respectively.
ΔJelly made from plantTo estimate the amount of frost heaving L is the longitudinal length of test specimen 17.
L0Is the initial length of the equivalent restraint module 10.
N is the number of turns of the spring of the equivalent restraint module 10. dBulletIs the diameter of the spring.
The test method is designed by adopting an elastic fulcrum method. The testing method can be used for evaluating the soil pressure of the side wall of the deep foundation pit in the cold region, and the testing method relates to the fact that the supporting rigidity of a foundation pit supporting structure (supporting piles 31, anchor cables 30, steel supports, steel enclosing purlins, crown beams 51, waist beams 32 and the like) is equivalent to the constraint rigidity of a testing device. The device comprehensively simulates the supporting structure constraint and the embedded end passive soil pressure of the foundation pit supporting structure on the inner side of the deep foundation pit through a spring with equivalent constraint stiffness, and performs equivalent calculation by considering the parameter characteristics of an anchor cable 30, a support pile 31, a waist beam 32 and the like between the ground and the bottom of the foundation pit to obtain the equivalent deformation stiffness K at a certain point of the deep foundation piteq。
Keq＝KGeneral assembly/Ck(7)。
Wherein, KGeneral assemblyThe comprehensive rigidity of the passive soil pressure at the restraining and embedding ends of the foundation pit supporting structure is achieved.
CkThe spring rate similarity coefficient.
The comprehensive rigidity of the passive soil pressure at the restraining and embedding ends of the foundation pit supporting structure is calculated according to the following formula.
Figure BDA0002468904650000121
Wherein, α1、α2、α3、α4The stiffness adjustment factor.
kiThe deformation rigidity of the ith anchor cable 30.
k′iThe deformation rigidity of each steel purlin is obtained.
n is the number of anchor cables 30.
Ks is the equivalent stiffness of the supporting pile body embedding end by the passive soil pressure.
Kp is the constraint rigidity of the supporting pile body.
Kg is the restraining stiffness of the crown beam 51.
According to on-site monitoring data, the temperatures at different depths of the deep foundation pit are found to have large differences, and the overall frost heaving development characteristics and the distribution rule of the deep foundation pit in time and space can be obtained through a plurality of groups of different temperature gradient tests. The temperature gradient range of the tested test sample 17 is (0.05-1) DEG C/cm. The stress state of the soil body after the cold end 13 of the heat exchange module is loaded with the soil body and frozen and swelled is shown in fig. 17, and the stress state of the soil sample is sigma from the lateral direction at normal temperature2In the axial direction is σ3After the initial stress state is converted into negative temperature loading, the stress state is sigma in the axial direction2And the lateral direction is sigma3Even in the axial and lateral directions are σ2And a stress state.
During the test, corresponding data collected by the horizontal axial force collecting sensor 3, the horizontal displacement sensor 23, the temperature sensor 16, the soil pressure sensor 42, the vertical displacement sensor 35 and the vertical load sensor 36 are transmitted to the data collecting system 39.
The water supplement amount of the test sample is recorded in the test process, the change condition of the water content of the test sample 17 before and after the test is sliced, analyzed and tested, the water migration rule is deeply analyzed, and the numerical analysis result is convenient to verify. The water replenishing system 22 may replenish water from the beginning of the cooling of the cold end 13 of the heat exchange module and the warm end 14 of the heat exchange module to the end of the test.

Claims (10)

1. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body is characterized by comprising the following steps of:
step 1, manufacturing a test sample (17), installing the test sample on a test platform (21), and arranging a left lateral restraint plate (5a), a right lateral restraint plate (5b) and sensors on the left lateral restraint plate (5a) and the right lateral restraint plate (5 b);
step 2, simulating a multidirectional stress field of a deep foundation pit soil body, and carrying out vertical loading, horizontal loading and consolidation on a test sample (17);
step 3, carrying out temperature loading on the test sample (17), and simulating a temperature field and a temperature gradient in a soil body of the test sample (17) according to the actual engineering condition;
step 4, simulating the deformation rigidity of the deep foundation pit supporting structure in the actual engineering through the equivalent constraint module (10); calculating an equivalent stiffness value according to the actual situation of the deep foundation pit supporting structure;
step 5, recording the water supplement amount of the test sample (17) in the test process; after the test is finished, the change condition of the water content of the test sample (17) before and after the test sample (17) is subjected to slice analysis test;
and 6, testing through multiple groups of different temperature gradients to obtain the overall frost heaving development characteristics and distribution rules of the deep foundation pit in time and space.
2. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body according to claim 1, which is characterized by comprising the following steps of:
the left lateral restraint plate (5a) and the right lateral restraint plate (5b) on the periphery of the test sample (17) are respectively coated with lubrication to reduce side friction resistance of the test sample (17) in a frost heaving process, and meanwhile, the cold end (13) and the warm end (14) of the heat exchange module are arranged at the rear end and the front end of the test sample (17) and are tightly attached to limit displacement of the warm end (14) of the heat exchange module.
3. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body according to claim 1, which is characterized by comprising the following steps of:
vertical loading final value in vertical loading: n is a radical ofVertical＝ρpj·g·H·a·L (1)；
Where ρ ispjSimulating the average density of all soil layers above the position;
g is the acceleration of gravity;
h is the depth of the simulated position;
a is the horizontal plane side length of the test sample (17), and L is the longitudinal side length of the test sample (17);
the test sample (17) can be converted to reach sigma in the vertical direction1Initial stress state:
σ1＝ρpj·g·H (2)；
horizontal load final value in horizontal load:
for static soil pressure conditions:
Nsp＝K0·σ1·a·b (3)；
wherein, K0＝1-sinφ；
For active soil pressure conditions:
Nsp＝(tan2(45-φ/2)·σa-2c·tan(45-φ/2))·a·b (4)；
wherein σaIs the active earth pressure at the simulated location.
4. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body according to claim 1, which is characterized by comprising the following steps of:
consolidation: after the test sample (17) is placed, the loading control system (38) is used for realizing the synchronous equal proportion loading of the test sample (17) in the vertical direction and the horizontal direction or loading according to a certain path so as to realize that the initial stress of the test sample (17) in the lateral direction and the horizontal orthogonal direction reaches the target state,
while loading, the data acquisition system (39) is started to acquire the deformation delta of the test sample (17) in the vertical direction and the horizontal direction1And Δ2；
The automatic loading control system (38) automatically adjusts loading according to the size of the soil sample or the stress change of the soil body, and keeps the position after consolidation in the horizontal loading direction unchanged.
5. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body according to claim 1, which is characterized by comprising the following steps of:
temperature loading: the cold end (13) and the warm end (14) of the heat exchange module reach low temperature of 0-2 ℃ by adjusting the cold end cold bath (19) and the warm end cold bath (20), the overall temperature field condition of the test sample (17) is monitored by the temperature sensors (16) distributed on the two sides of the test sample (17), when the overall temperature field of the test sample (17) reaches consistency and uniform distribution, the cold end cold bath (19) temperature is reduced to achieve the purpose of reducing the cold end (13) of the heat exchange module, and finally the cold end (13) temperature of the heat exchange module is stabilized at the simulated environment temperature; along with the reduction of the temperature of the cold end (13) of the heat exchange module, the test sample (17) begins to be gradually frozen at the cold end and generates a frost heaving phenomenon due to the migration and phase change of water; the total frost heaviness delta is estimated before testingJelly made from plantThe frost heaving compression deformable quantity delta of the equivalent constraint module (10) meets the following condition:
Δ≥2(Nsp/Keq-Nsp·L/(a·b·Esoil for soil)+ΔJelly made from plant) (5)；
The initial length of the equivalent constraint module (10) should satisfy the following condition:
L0≥n·dbullet+Δ (6)；
Wherein, Delta is the compressible deformation of the equivalent constraint module (10);
Nspinitially loading a numerical value for a horizontal loading system;
Keqthe rigidity of the spring hooke is equivalent converted according to a deep foundation pit supporting system;
Esoil for soilTo test the compression modulus of the test specimen (17); a. b are respectively the cross-sectional dimension of the test sample (17);
Δjelly made from plantL is the longitudinal length of the test sample (17);
L0is the initial length of the equivalent restraint module (10);
n is the number of spiral turns of the spring of the equivalent restraint module (10); dBulletIs the diameter of the spring.
6. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body according to claim 1, which is characterized by comprising the following steps of:
calculation of equivalent stiffness: the test method is designed by adopting an elastic fulcrum method; the testing method can be used for evaluating the soil pressure of the side wall of the deep foundation pit in the cold region, and relates to the technical scheme that the supporting rigidity of the deep foundation pit supporting structure is equivalent to the constraint rigidity of a testing device; the device comprehensively simulates the supporting structure constraint and the embedded end passive soil pressure of a pile body on the inner side of a foundation pit through a spring with equivalent constraint stiffness, and performs equivalent calculation by considering the parameter characteristics of the supporting structure of the deep foundation pit between the ground and the bottom of the deep foundation pit to obtain the equivalent deformation stiffness K at a certain point of the deep foundation piteq；
Keq＝KGeneral assembly/Ck(7)；
Wherein, KGeneral assemblyThe comprehensive rigidity of the passive soil pressure at the restraining and embedding ends of the foundation pit supporting structure is provided;
Ckis the spring stiffness similarity coefficient;
the comprehensive rigidity of the restraint of the deep foundation pit supporting structure and the passive soil pressure of the embedded end is calculated according to the following formula;
Figure FDA0002468904640000031
wherein, α1、α2、α3、α4Adjusting coefficient for stiffness
kiThe deformation rigidity of the ith anchor cable (30) is obtained;
k′ithe deformation rigidity of each steel purlin is obtained;
n is the number of anchor cables (30);
ks is the passive soil pressure equivalent stiffness of the embedding end of the supporting pile body;
kp is the constraint rigidity of the supporting pile body;
kg is the restraining rigidity of the crown beam (51).
7. The method for testing the water-heat-force coupling soil pressure by using the multidirectional stress field of the cold region soil body according to claim 1, which is characterized by comprising the following steps of:
water replenishing system (22): the water supply bottle (47) is connected with the inlet of the drip tube (46); filter paper (48) is arranged between the rear part of the shell of the warm end (14) of the heat exchange module and the test sample (17); a permeable stone (49) is arranged below the test sample (17); the permeable stone (49) is arranged in the open groove of the test platform (21), and a water collecting tank (50) is arranged below the permeable stone (49); the water collecting tank (50) is fixed below the test platform (21); water enters the drip tube (46) from the water supply bottle (47) by means of gravity, and filter paper (48) is soaked at the contact position of the test sample (17) at the water supply hole (45) and the shell of the warm end (14) of the heat exchange module; continuously introducing water by using a dropper (46) through external water supply, and allowing the excessive water to pass through a permeable stone (49) at the lower end of the test sample (17) under the action of gravity and enter a water collecting tank (50);
the water supply bottle (47) and the water collection tank (50) are respectively provided with water volume scales, and the water volume absorbed by the soil body is calculated according to the water supply volume and the water collection volume in the test process;
recording the water supplement amount of the test sample in the test process, and slicing the test sample (17) after the test is finished; the change condition of the water content of the sample before and after the analysis test deeply analyzes the rule of water migration, and is convenient for verifying the numerical analysis result.
8. Cold region soil body multidirectional stress field water-heat-power coupling soil pressure testing arrangement has test platform (21), its characterized in that: a horizontal loading system and a vertical loading system are arranged on the test platform (21);
the horizontal loading system comprises a horizontal power device, a horizontal dowel bar (25), a horizontal axial force acquisition sensor (3), a horizontal displacement sensor (23), a directional plate (7), a propulsion plate (9), an equivalent constraint module (10), a horizontal guide rail (11), a loading frame (12), a heat exchange module cold end (13), a lateral constraint plate (5) and a heat exchange module warm end (14);
the output part of the horizontal power device is connected with the rear end of the horizontal dowel bar (25);
the horizontal power device is fixedly arranged on the test platform (21);
an orientation plate (7) is fixed on the test platform (21), and a horizontal dowel bar (25) penetrates through a dowel bar hole (28) in the middle of the orientation plate (7);
the front end of the horizontal dowel bar (25) is fixedly connected with a propelling plate (9); the pushing plate (9) is positioned in front of the orientation plate (7);
the pushing plate (9) is sleeved on the horizontal guide rail (11) through a pushing plate hole (43), and the horizontal guide rail (11) penetrates through a guide rail hole (29) of the directional plate on the directional plate (7);
a horizontal shaft force acquisition sensor (3) is arranged on the horizontal dowel bar (25);
the horizontal displacement sensor (23) is positioned between the orientation plate (7) and the propulsion plate (9);
the front end of the horizontal guide rail (11) is fixedly connected with a loading frame (12);
the front end of the loading frame (12) is contacted with a shell of a cold end (13) of the heat exchange module;
the front of the cold end (13) of the heat exchange module is an area for placing a test sample (17);
an equivalent restraint module (10) is arranged on the horizontal guide rail (11), and the equivalent restraint module (10) is positioned between the propulsion plate (9) and the loading frame (12);
a warm end (14) of a heat exchange module is fixedly arranged in front of the area for placing the test sample (17);
vertical lateral restraint plates (5) are fixedly arranged on the left side and the right side of the area for placing the test sample (17);
a temperature sensor (16) and a soil pressure sensor (42) are arranged on the lateral restraint plate (5);
a vertical loading system: the vertical loading system comprises a reaction frame (1), a vertical power device, a vertical load sensor (36), a vertical loading rod (37), a cover plate (4) and a vertical displacement sensor (35);
a vertical power device is fixed below a transverse bracket (1a) of the reaction frame (1);
the output part of the vertical power device is connected above the vertical loading rod (37);
a cover plate (4) is fixed at the lower end of the vertical loading rod (37);
the vertical load sensor (36) is positioned on the vertical loading rod (37);
the vertical displacement sensor (35) is positioned above the cover plate (4) and between a bracket (44) fixed on the test platform (21);
the cover plate (4) is positioned in the area above the test sample (17);
the area for placing the test sample (17) is provided with a water replenishing system (22).
9. The cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing device of claim 8, wherein: water replenishing system (22): a plurality of water supply holes (45) are formed in the rear of the shell of the warm end (14) of the heat exchange module, a plurality of drip pipes (46) are arranged in the shell of the warm end (14) of the heat exchange module, and outlets of the drip pipes (46) are correspondingly connected with the water supply holes (45);
the water supply bottle (47) is connected with the inlet of the drip tube (46);
filter paper (48) is arranged between the rear part of the shell of the warm end (14) of the heat exchange module and the test sample (17);
a permeable stone (49) is arranged below the test sample (17); the permeable stone (49) is arranged in the groove of the test platform (21);
a water collecting tank (50) is arranged below the permeable stone (49).
10. The cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing device of claim 8, wherein:
the horizontal power device is a horizontal stepping guide rail (8), and the rear end of the horizontal dowel bar (25) is fixed at the output part of the horizontal stepping guide rail (8);
the vertical power device is a vertical loading motor (2) which is in threaded connection with the upper part of a vertical loading rod (37);
a guide block (52) is arranged on the vertical loading rod (37), a guide frame (53) is arranged below the transverse support (1a), a vertical guide groove (54) is formed in the guide frame (53), and the guide block (52) is positioned in the guide groove (54);
the equivalent restraint module (10) is a spring; a camera (27) is arranged on the test platform (21).
CN202010342172.2A 2020-04-27 2020-04-27 Cold region soil body multidirectional stress field water-heat-force coupling soil pressure testing method and device Pending CN111474063A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111948031A (en) * 2020-09-24 2020-11-17 吉林大学 Soil body direct shear test device considering water heating power salt coupling effect
CN112577833A (en) * 2020-12-29 2021-03-30 哈尔滨工业大学 Multilayer reinforced soil drawing tester suitable for coarse-grained filler of cold region roadbed
CN114018970A (en) * 2021-11-08 2022-02-08 哈尔滨工业大学 Multifunctional freezing low-temperature model test device for cold region

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111948031A (en) * 2020-09-24 2020-11-17 吉林大学 Soil body direct shear test device considering water heating power salt coupling effect
CN112577833A (en) * 2020-12-29 2021-03-30 哈尔滨工业大学 Multilayer reinforced soil drawing tester suitable for coarse-grained filler of cold region roadbed
CN114018970A (en) * 2021-11-08 2022-02-08 哈尔滨工业大学 Multifunctional freezing low-temperature model test device for cold region
CN114018970B (en) * 2021-11-08 2024-02-09 哈尔滨工业大学 Multifunctional freezing low-temperature model test device for cold region

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