CN114858616A - Loess structure collapsibility nondestructive test device under water-heat-power coupling - Google Patents
Loess structure collapsibility nondestructive test device under water-heat-power coupling Download PDFInfo
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- CN114858616A CN114858616A CN202210448712.4A CN202210448712A CN114858616A CN 114858616 A CN114858616 A CN 114858616A CN 202210448712 A CN202210448712 A CN 202210448712A CN 114858616 A CN114858616 A CN 114858616A
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- 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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/18—Performing tests at high or low temperatures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
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- 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
- G01N3/02—Details
- G01N3/06—Special adaptations of indicating or recording means
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- 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
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
- G01N3/10—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces generated by pneumatic or hydraulic pressure
- G01N3/12—Pressure testing
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- G—PHYSICS
- 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
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G—PHYSICS
- 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
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0222—Temperature
- G01N2203/0226—High temperature; Heating means
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- G—PHYSICS
- 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
- G01N2203/02—Details not specific for a particular testing method
- G01N2203/022—Environment of the test
- G01N2203/0236—Other environments
Abstract
The invention discloses a water-heat-force coupling lower loess structure collapse nondestructive testing device, which comprises a pressure chamber, a consolidation box, a loading unit and an electric heating unit, wherein the pressure chamber is a closed cavity, and the bottom of the pressure chamber is provided with a water inlet and a water outlet which are communicated with the interior of the consolidation box; the consolidation box comprises a pressure plate, a permeable stone, a cutting ring and a clay plate, wherein the permeable stone is provided with a bending element transmitting end and extends into the consolidation box; the cutting ring is arranged below the permeable stone opposite to the permeable stone to form a consolidation box body; the argil plate is arranged below the cutting ring to form a consolidation box bottom plate, and the argil plate is provided with a bending element receiving end and extends into the box; the loading unit is a loading rod penetrating through the top of the pressure chamber; the electric heating unit is used for heating the loess sample in the consolidation box body. The invention can detect the change characteristic of the loess collapsible structure in a high stress environment, has high heating efficiency, can conveniently control different loess collapsible temperature environments, and realizes continuous nondestructive quantitative detection of different stages of the loess collapsible structure overall process.
Description
Technical Field
The invention belongs to the technical field of soil detection, and particularly relates to a lower loess structure collapse nondestructive detection device for water-heat-force coupling.
Background
Loess is a special unsaturated soil and widely distributed in China. Under the action of geological deposition environment, loess has a special soil body structure, so that the loess has a remarkable collapsible characteristic, namely, the loess is soaked by water under a certain pressure, the structure of the loess is rapidly destroyed, and a remarkable additional subsidence characteristic is generated. Loess collapsibility can cause multiple geological disasters such as ground subsidence, ground surface fracture, side slope unstability, uneven settlement, and the like, and great challenges are brought to the smooth development of engineering construction and disaster prevention and reduction work in loess areas.
The consolidation apparatus is an industrial apparatus, is divided into a saturation consolidation apparatus and a non-saturation consolidation apparatus, can perform a normal slow consolidation test and a rapid consolidation test, is generally used for measuring the compression performance of soil under different loads and limited conditions, and detecting parameters such as early consolidation pressure, compression index, resilience index and the like of a soil body. In the case of loess, a consolidation test can measure the collapsible property parameters such as the collapsible coefficient and the collapse starting pressure, and is generally used for detecting the collapsible property of loess.
The existing loess structure collapse detection technology is generally single to the control means of collapse environmental factors, such as the traditional unsaturated consolidation apparatus and the unsaturated consolidation apparatus additionally provided with a bending element probe, can detect the deformation characteristic and the small strain shear modulus of the collapsed loess, but only can control the change of the load and the water containing condition of the loess, and neglects the influence of the temperature environment. More importantly, even if install temperature control device's unsaturated consolidometer additional, loess collapsible deformation characteristic under detectable load, moisture condition and the temperature environment condition change condition, current loess structure collapsible detection technique only can be after the collapsible is accomplished, through carrying out further destruction sample to the soil body, just can carry out contrastive analysis to the soil body structure around the collapsible. Therefore, the prior art does not form a multi-factor coupling detection technology for the loess structure collapse, and lacks a nondestructive detection method for realizing continuous detection of different stages of the whole structural collapse process.
In addition, it is worth noting that the existing unsaturated temperature control consolidometer adopts a water bath heating method to control the temperature of the sample, and the sample temperature is relatively constant for a long time through the characteristic of high specific heat capacity of water, but the heating equipment and the method are lagged behind, the temperature cannot be accurately controlled, the heating time is long, and the test period is prolonged.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a loess structure collapse nondestructive testing device under the water-heat-force coupling effect, which can conveniently realize nondestructive quantitative detection on deformation characteristics and structural change characteristics of loess collapse process under the water-heat-force coupling effect.
The invention is realized by the following steps:
the invention firstly provides a loess structure collapse nondestructive testing device under the water-heat-force coupling effect, which comprises a pressure chamber, a consolidation box, a loading unit and an electric heating unit, wherein:
the pressure chamber is a closed chamber, the top of the pressure chamber is provided with an air inlet communicated with the inside of the pressure chamber, and the bottom of the pressure chamber is provided with a water inlet and a water outlet communicated with the inside of the consolidation box;
the consolidation box is arranged in the pressure chamber and comprises a pressure plate, a permeable stone, a cutting ring and a clay plate, and the consolidation box comprises:
the pressurizing plate is superposed on the permeable stone to form a top cover of the consolidation box together with the permeable stone, the permeable stone is provided with a bent element transmitting end and extends into the box, and the bent element transmitting end and the permeable stone are sealed;
the cutting ring is arranged below the permeable stone opposite to the permeable stone to form a consolidation box body, and a loess sample is placed in the consolidation box body;
the argil plate is arranged on a pressure chamber base below the cutting ring to form a consolidation box bottom plate, a bending element receiving end is arranged on the argil plate and extends into the box, and the bending element receiving end and the argil plate are sealed;
the loading unit is formed by a loading rod which penetrates through the top of the pressure chamber and is vertically opposite to the pressurizing plate, and the loading rod is sealed with the top of the pressure chamber;
the electric heating unit is used for heating the loess sample in the consolidation box body.
In some embodiments, the permeable stone is provided with a through hole for the emission end of the bending element to pass through, one end of the emission end of the bending element is fixedly arranged on the pressurizing plate, the other end of the emission end of the bending element passes through the through hole, and the through hole is filled with epoxy resin;
a through hole for the receiving end of the bending element to pass through is formed in the argil plate, one end of the receiving end of the bending element is fixedly installed at the bottom of the pressure chamber, the other end of the receiving end of the bending element passes through the through hole, and epoxy resin is filled in the through hole.
In some embodiments, the bending element emitting end is mounted on the pressure plate through a sealing unit, the sealing unit comprises a fixed shell, a fixed body and epoxy resin, the fixed shell is a cylindrical structure with one end being provided with a bottom, the bottom end of the bending element emitting end is fixedly mounted at the bottom of the fixed shell through the fixed body, a lead of the bending element emitting end penetrates out of the bottom of the fixed shell, the top end of the bending element emitting end protrudes out of the fixed shell, and the rest space in the fixed shell is filled with the epoxy resin; a sealing ring is arranged outside the fixed shell, a through hole for the fixed shell to pass through is formed in the permeable stone, and the fixed shell and the through hole are sealed through the sealing ring;
the receiving end of the bending element is arranged at the bottom of the pressure chamber in the same way, and the argil plate is provided with a through hole for the fixed shell to pass through;
preferably, the bottom end of the transmitting end of the bending element is positioned at the fixed body, the length of the bottom end of the fixed body is not more than three quarters of the length of the transmitting end of the bending element, and the length of the top end of the transmitting end of the bending element protruding out of the fixed shell is 2-3 mm;
the bottom end of the bent element receiving end is positioned at the fixed body, the length of the fixed body does not exceed three quarters of the length of the bent element receiving end, and the length of the top end of the bent element receiving end protruding out of the fixed shell is 2-3 mm;
preferably, the fixing body is made of plastic.
In some embodiments, the apparatus further comprises a thermocouple disposed at the bottom of the pressure chamber and centered on the clay plate, the thermocouple extending through the clay plate and into the consolidation box, the thermocouple sealed to the clay plate.
In some embodiments, the electric heating unit adopts an electric heating ring, is arranged at the periphery of the cutting ring in the pressure chamber and comprises an annular shell and a heating wire, the annular shell is provided with an inner cavity, the heating wire is arranged in the inner cavity, the annular shell is coaxially arranged with the clay plate, and the inner diameter of the annular shell is not less than the diameter of the clay plate; the lower end of the annular shell is hermetically connected with the bottom of the pressure chamber;
preferably, the lower extreme of annular housing and the bottom of pressure chamber can dismantle sealing connection between, the lower extreme of annular housing establishes to the step, and the surface cover of step is equipped with the sealing washer, and the bottom of pressure chamber is equipped with the recess that is used for imbedding the step.
In some embodiments, the pressure chamber comprises a pressure chamber upper cover, an annular side wall and a pressure chamber base, the pressure chamber upper cover and the pressure chamber base are fixedly connected to the top and the bottom of the annular side wall through bolts, and sealing rings are arranged on the contact surface of the pressure chamber upper cover and the top of the annular side wall and the contact surface of the pressure chamber base and the bottom of the annular side wall;
preferably, the clay plate is arranged on the pressure chamber base and positioned in the center of the annular side wall, the thermocouple and the bending element receiving end are both arranged on the pressure chamber base, and a pore passage for leading out of the thermocouple and the bending element receiving end is arranged on the pressure chamber base;
preferably, the water inlet and the water outlet are arranged on the pressure chamber base.
In some embodiments, the device further comprises a gas circulating pump, a water inlet and outlet controller and a temperature controller, wherein the gas circulating pump is connected with the gas inlet, the water inlet and outlet controller is connected with the water inlet and the water outlet, and the electric heating ring and the thermocouple are connected with the temperature controller.
In some embodiments, the bending element further comprises a signal generator and an oscilloscope, wherein the bending element transmitting end is connected with the signal generator, and the bending element receiving end is connected with the oscilloscope.
In some embodiments, the device further comprises a displacement sensor which is arranged on the loading rod, and a probe of the displacement sensor is in contact with the top of the pressure chamber.
The invention also provides a loess structure collapse nondestructive detection method under the water-heat-force coupling effect, which is based on the detection device and comprises the following steps:
(1) preparing a sample with a certain size, taking the sample with the required size from the bulk soil sample by using a cutting ring for the bulk soil sample taken back in situ, and putting the soil sample wrapped by the cutting ring into a pressure chamber to finish a sample loading process;
(2) the bending element transmitting end and the bending element receiving end are connected with the air inlet, the water inlet and the water outlet;
(3) applying a load to a target load, and monitoring the collapse process in real time;
(4) setting a target temperature, and keeping the temperature stable all the time in the process of collapse;
(5) applying set water pressure to the pressure chamber until the water inlet volume is stable to realize the control of the initial water containing condition of the soil sample, and applying set air pressure to the pressure chamber to enable the air to uniformly act on the upper surface of the sample through the permeable stone holes until the required matrix suction force is achieved;
(6) the bending element transmitting end excites a signal, and the bending element receiving end receives the signal, so that the measurement of the initial small strain shear modulus of the soil body and the nondestructive detection of the initial structure are realized;
(7) changing the water pressure applied to the pressure chamber to simulate the next stage of the collapse process, repeating the step (6) to excite and record the primary bending element signal after the water inlet volume is stable, and realizing the measurement of the small strain shear modulus of the soil body in the collapse stage and the nondestructive detection of the structural collapse;
(8) and (5) repeating the step (7) until the soil sample is saturated, and realizing the determination of the soil body shear modulus at different stages in the total process of the loess structure collapse and the nondestructive detection of the total process of the structure collapse.
Compared with the prior art, the invention has the beneficial effects that:
the closed pressure chamber can bear higher pressure, and the change characteristic of the loess collapsible structure in a high-stress environment can be detected. Through setting up electrical heating ring, the cutting ring can be placed to electrical heating ring inside, and the electrical heating ring can directly heat the soil in the cutting ring, has improved heating efficiency, and the cooperation thermocouple utilizes the thermocouple to carry out real-time temperature detection to the soil in the cutting ring, can heat the soil rapid heating in the cutting ring to predetermineeing the temperature, can conveniently realize the detection of loess collapsible structure under the different temperatures, because the temperature has great influence to the intensity and the collapsibility of unsaturated loess. Through introducing crooked first system, to the measurement of the change condition of the shear modulus of strain in the loess collapsible process, realize the continuous nondestructive quantitative determination to loess structure collapsible overall process different stages.
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 should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so that those skilled in the art can understand and read the present invention, and do not limit the conditions for implementing the present invention, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the functions and purposes of the present invention, shall fall within the scope covered by the technical contents disclosed in the present invention.
FIG. 1 is a schematic view of a main body portion of a detecting device according to an embodiment of the present invention;
FIG. 2 is a partial cross-sectional view of a consolidation box in an embodiment of the invention;
FIG. 3 is a schematic view of a bending element probe in accordance with an embodiment of the present invention;
FIG. 4 is a cross-sectional view of an electrical heating ring according to an embodiment of the present invention;
FIG. 5 is a schematic view of the overall inspection apparatus according to one embodiment of the present invention;
wherein: 1-loading rod, 2-loading rod head, 3-displacement sensor, 4-air inlet, 5-bending element emitting end lead wire, 6-pressurizing plate, 7-bending element emitting end, 8-cutting ring, 9-electric heating ring, 9-1-annular shell, 9-2-electric heating wire, 9-3-step, 10-permeable stone, 11-thermocouple, 12-bending element receiving end, 13-thermocouple and bending element receiving end lead wire, 14-water inlet, 15-water outlet, 16-clay plate, 17-pressure chamber base, 18-connecting bolt, 19-pressure chamber upper cover, 20-air circulating pump, 21-water inlet and outlet controller, 22-loading frame, 23-signal amplifier and 24-oscilloscope, 25-temperature controller, 26-sealing ring, 27-epoxy resin, 28-fixed shell and 29-fixed body.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the present invention is described in further detail below with reference to the embodiments and the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
In the description of the present invention, the terms "comprises/comprising," "consisting of … …," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a product, apparatus, process, or method that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such product, apparatus, process, or method if desired. Without further limitation, an element defined by the phrases "comprising/including … …," "consisting of … …," or "comprising" does not exclude the presence of other like elements in a product, device, process, or method that comprises the element.
It is to be understood that, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are intended to be open-ended, i.e., to mean either a fixed connection, a removable connection, or an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
It will be further understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," "outer," "center," and the like are used in an orientation or positional relationship illustrated in the drawings for convenience in describing and simplifying the invention, and do not indicate or imply that the device, component, or structure being referred to must have a particular orientation, be constructed in a particular orientation, or be operated in a particular manner, and should not be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The following describes the implementation of the present invention in detail with reference to preferred embodiments.
Referring to fig. 1, a loess structure collapsibility nondestructive testing apparatus under water-heat-force coupling, includes a pressure chamber, a consolidation box, a loading unit and an electric heating unit, wherein:
the pressure chamber is a closed chamber, the top of the pressure chamber is provided with an air inlet 4 communicated with the inside of the pressure chamber, and the bottom of the pressure chamber is provided with a water inlet 14 and a water outlet 15 communicated with the inside of the consolidation box;
the consolidation box is arranged in the pressure chamber and comprises a pressure plate 6, a permeable stone 10, a cutting ring 8 and a clay plate 16, and the consolidation box comprises:
the pressure plate 6 is superposed on the permeable stone 10 and forms a top cover of the consolidation box together with the permeable stone 10, the permeable stone 10 is provided with a bent element transmitting end 7 and extends into the box, and the bent element transmitting end 7 is sealed with the permeable stone 10;
the cutting ring 8 is arranged below the permeable stone 10 opposite to the permeable stone 10 to form a consolidation box body, and a loess sample is placed in the consolidation box body;
the argil plate 16 is arranged on a pressure chamber base below the cutting ring 8 to form a consolidation box bottom plate, the argil plate 16 is provided with a bending element receiving end 12 and extends into the box, and the bending element receiving end 12 is sealed with the argil plate 16;
the loading unit is characterized in that a loading rod 1 penetrates through the top of the pressure chamber and is vertically opposite to the pressurizing plate 6, and the loading rod 1 and the top of the pressure chamber are sealed;
the electric heating unit is used for heating the loess sample in the consolidation box body.
The invention provides the soil sample historical stress through the loading rod, simulates the humidification process through the lower water inlet, provides the air pressure through the air inlet so that the air pressure of the pores in the soil sample reaches a set value, and then obtains the required matrix suction by matching with the water pressure, wherein the matrix suction is an important angle for analyzing the collapsibility of unsaturated yellow soil.
In addition, the temperature has a great influence on the strength of unsaturated loess, and when the temperature is higher than 0 ℃, the shear strength of a soil body can be increased along with the increase of the temperature, mainly because the viscosity of water is reduced along with the increase of the temperature, the permeability coefficient is increased, the void ratio of the soil is reduced, and the strength is increased along with the decrease of the viscosity of the water. The loess collapsibility test device reflects the collapsibility, the temperature is increased, the soil body structure is further damaged, the soil body agglomeration degree is increased, and the collapsibility is enhanced.
Referring to fig. 2, in the invention, a through hole for the bending element emitting end 7 to pass through is formed on the permeable stone 10, one end of the bending element emitting end 7 is fixedly installed on the pressurizing plate 6, the other end of the bending element emitting end passes through the through hole, and the through hole is filled with epoxy resin 27; the pottery clay plate 16 is provided with a through hole for the bending element receiving end 12 to pass through, one end of the bending element receiving end 12 is fixedly arranged at the bottom of the pressure chamber, the other end of the bending element receiving end 12 passes through the through hole, and the through hole is filled with epoxy resin 27. Through set up the through-hole at permeable stone 10 and argil board 16, wear to establish bending element transmitting terminal 7 and bending element receiving terminal 12, bending element transmitting terminal 7, bending element receiving terminal 12 snap-on are on the bottom of increased pressure board 6, pressure chamber, and the structure is simpler, simple to operate.
Further, since the bent element piece of the bent element emitting end is fragile and easily damaged during use, the bent element emitting end of the present invention is mounted to the pressing plate 6 through a sealing unit to improve the reliability of mounting and sealing.
As shown in fig. 3, in one embodiment, the sealing unit includes a fixed housing 28, a fixed body 29 and an epoxy resin 27, the fixed housing 28 is a cylindrical structure with one end being closed, the bottom is upward in the drawing, the bottom end of the bending element emitting end 7 is fixedly installed at the bottom of the fixed housing through the fixed body 29, the lead of the bending element emitting end 7 penetrates out from the bottom of the fixed housing, the top end of the bending element emitting end 7 protrudes out of the fixed housing, and the rest space in the fixed housing is filled with the epoxy resin 27; a sealing ring 26 is arranged outside the fixed shell, a through hole for the fixed shell to pass through is formed in the permeable stone 10, and the fixed shell and the through hole are sealed through the sealing ring 26; the fixing body wraps the bent element sheet, and the fixing body is only required to be aligned with a hole which is punched in advance in the bottom permeable stone and then integrally inserted into the hole during installation, so that the usability of the installed bent element after the emitting end is ensured, the installation is convenient, and on the other hand, if the material of the bent element sheet is damaged or needs to be replaced after the bent element sheet is used for a period of time to keep the precision, the bent element sheet can be replaced after being plugged and connected at any time when the bent element sheet has a problem, and the method is superior to the conventional method that the bent element sheet cannot be replaced when being fixed in the center of the base.
Similarly, the bender receiver 12 is mounted to the bottom of the pressure chamber in the same manner and the clay plate 16 is provided with a through hole for the mounting housing to pass through.
In the present invention, the fixing body 29 is made of plastic, and the plastic body can effectively fix the bent element without damaging the bent element.
Furthermore, the bottom end of the bent element transmitting end 7 is positioned at the fixed body, the length of the fixed body is not more than three quarters of the length of the bent element transmitting end 7, and the length of the top end of the bent element transmitting end 7 protruding out of the fixed shell is 2-3 mm; the length of the bottom end of the transmitting end of the bending element, which is positioned on the fixed body, is not more than three-fourths of the length of the transmitting end of the bending element, so that the vibration of the transmitting end of the bending element can be ensured, and the received signal is good; the length of the top end of the bent element transmitting end protruding out of the fixed shell is 2-3mm, when the bent element transmitting end is installed, the end face of the fixed shell is generally aligned with the surface of the permeable stone 10, so that the length of the part of the top end of the bent element transmitting end 7 extending into the soil body in the cutting ring can be ensured to be 2-3mm, measurement can be ensured, excessive disturbance of the bent element transmitting end to the soil body in the cutting ring can be prevented, the measurement result is more accurate, and the measurement effect is ensured.
The bottom end of the bent element receiving end 12 is located at the fixed body, the length of the fixed body is no more than three-quarters of the length of the bent element receiving end 12, and the length of the top end of the bent element receiving end 12 protruding out of the fixed shell is 2-3 mm. The length of the bottom end of the bending element receiving end, which is positioned on the fixed body, is not more than three quarters of the length of the bending element receiving end, so that the vibration of the bending element receiving end can be ensured, a received signal is good, the length of the top end of the bending element receiving end, which protrudes out of the fixed shell, is 2-3mm, and the end face of the fixed shell is generally aligned with the surface of the argil plate 16 during installation, so that the length of the part of the top end of the bending element receiving end 12, which extends into the soil body in the cutting ring, is 2-3mm, so that the measurement can be ensured, the excessive disturbance of the bending element receiving end to the soil body in the cutting ring can be prevented, the measurement result is more accurate, and the measurement effect is ensured.
Furthermore, the invention also comprises a thermocouple 11 which is arranged at the bottom of the pressure chamber and is positioned in the center of the argil plate 16, the thermocouple 11 penetrates through the argil plate 16 and extends into the consolidation box, and the thermocouple 11 and the argil plate 16 are sealed. Utilize the thermocouple to carry out real-time temperature detection to the soil in the cutting ring, cooperation electrical heating unit can be with the soil body rapid heating in the cutting ring to predetermineeing the temperature, conveniently realizes the detection of loess collapsible structure under the different temperatures.
As shown in figure 4, in one embodiment, the electric heating unit adopts an electric heating ring 9 which is arranged at the periphery of a cutting ring 8 in the pressure chamber and comprises an annular shell 9-1 and a heating wire 9-2, wherein the annular shell 9-1 is provided with an inner cavity, the heating wire 9-2 is arranged in the inner cavity, the annular shell 9-1 is coaxially arranged with a clay plate 16, and the inner diameter of the annular shell 9-1 is not smaller than the diameter of the clay plate 16; the lower end of the annular shell 9-1 is hermetically connected with the bottom of the pressure chamber. Through setting up electrical heating ring, the cutting ring can be placed to electrical heating ring inside, utilizes the electrical heating ring can directly heat the soil body in the cutting ring, has improved heating efficiency.
Furthermore, the lower end of the annular shell 9-1 is detachably and hermetically connected with the bottom of the pressure chamber, the lower end of the annular shell 9-1 is provided with a step 9-3, the outer surface of the step 9-3 is sleeved with a sealing ring 26, and the bottom of the pressure chamber is provided with a groove for embedding the step 9-3. The step and groove structure facilitates the rapid installation of the annular shell 9-1, and the outer surface is matched with the sealing ring 26 to facilitate the sealing connection with the bottom of the pressure chamber.
With continued reference to fig. 1, in the present invention, the pressure chamber includes a pressure chamber upper cover 19, an annular side wall and a pressure chamber base 17, the pressure chamber upper cover 19 and the pressure chamber base 17 are connected and fixed on the top and the bottom of the annular side wall through bolts 18, and sealing rings are respectively disposed on the contact surface of the pressure chamber upper cover 19 and the top of the annular side wall and the contact surface of the pressure chamber base 17 and the bottom of the annular side wall. A stable pressure chamber space is formed by the upper cover, the side walls, the base and the matched sealing structure, the whole structure is located on a larger loading frame 22, and the base with larger self weight serves as a support. The loading rod and the pressure chamber upper cover are assembled to cover the base integrally, and are connected with the base through four long bolts, and sealing is formed through an O-shaped ring on the base. The substrate suction control part is connected with the pressure chamber through a pipeline, and the temperature control part is connected with the base.
Further, the clay plate 16 is arranged on a pressure chamber base 17 and is positioned in the center of the annular side wall, the thermocouple 11 and the bending element receiving end 12 are both arranged on the pressure chamber base 17, and a pore passage through which a lead of the thermocouple 11 and the bending element receiving end 12 passes is arranged on the pressure chamber base 17;
further, the water inlet 14 and the water outlet 15 are opened on the pressure chamber base 17.
Referring to fig. 5 again, the present invention further includes a gas circulation pump 20, a water inlet and outlet controller 21, and a temperature controller, wherein the gas circulation pump 20 is connected to the gas inlet 4, the water inlet and outlet controller 21 is connected to the water inlet 14 and the water outlet 15, and the electric heating ring 9 and the thermocouple 11 are connected to the temperature controller. The gas circulating pump 20 applies set air pressure to the pressure chamber through the air inlet 4 at the upper cover 19 of the pressure chamber, and the gas uniformly acts on the upper surface of the sample through the permeable stone holes to control the suction force of the sample; the target temperature is set through a temperature controller, and the stability is always kept in the process of collapse; the water inlet and outlet controller 21 applies a set water pressure to the pressure chamber through the water inlet 14, and after the water inlet volume is stable, the initial water-containing condition control of the soil sample is realized.
Furthermore, the invention also comprises a signal generator 23 and an oscilloscope 24, wherein the bent element transmitting end 7 is connected with the signal generator 23, and the bent element receiving end 12 is connected with the oscilloscope 24. The lead wires of the bending element transmitting end 7 and the bending element receiving end 12 are respectively connected with a signal generator and an oscilloscope, the bending element transmitting end excites signals to be received by the bending element receiving end and the oscilloscope, images are formed on the oscilloscope, and the measurement of the initial small strain shear modulus of the soil body and the nondestructive detection of the initial structure are realized.
As shown in fig. 1, the present invention further includes a displacement sensor 3 mounted on the loading rod 1, the probe of which is in contact with the top of the pressure chamber. The displacement sensor adopts an LVDT (linear variable differential transformer), the LVDT is installed on a loading rod, an iron core of the LVDT is in contact with the top of the pressure chamber, and the displacement sensor measures the vertical displacement change of the sample and records the change data at the same time.
Referring to fig. 1 to 5, in the loess structure settlement nondestructive testing device, a loading rod 1 is arranged on an upper cover 19 of a pressure chamber, a displacement transducer LVDT is arranged on the loading rod 1, a head 2 of the loading rod is screwed at the lower end of the loading rod 1, a cutting ring 8 is arranged in a heating ring 9, the cutting ring 8 is arranged on an argil plate 16, the argil plate 16 is embedded in the center of the upper surface of a base 17 of the pressure chamber, a soil sample is arranged in the cutting ring 8, and a permeable stone 10 is adhered to a pressurizing plate 6 and is arranged on the soil sample.
The thermocouple 11 was mounted in the center of the clay plate 16 with the tip exposed to the clay plate by 3mm, and sealed with an O-ring and epoxy resin between the clay plate 16.
As shown in fig. 2, one way to mount the curved element transmitting end 7 and the curved element receiving end 12 is: the bottom of the bending element receiving end 12 is arranged on a pressure chamber base 17, holes are punched at corresponding positions of the clay plate 16 to expose the head of the bending element receiving end 12, and epoxy resin is used for filling the hole so as to facilitate the fixing and sealing of the bending element. The bottom of the bending element emitting end 7 is arranged on a pressurizing plate 6, a hole is formed in the corresponding position of the permeable stone, the emitting end is exposed, and the hole opening is filled with epoxy resin. The height of the permeable stone 10 exposed at the head of the transmitting end 7 of the bending element is 3mm, and the height of the argil plate 16 exposed at the head of the receiving end 12 of the bending element is 3 mm.
As shown in fig. 3, another installation method of the curved element transmitting end 7 and the curved element receiving end 12 is as follows: crooked unit transmitting terminal 7 and the 12 tops of receiving terminal expose epoxy 3mm, crooked unit bottom 5mm adopts the plastic body parcel, and the plastic body neither can damage crooked unit piece, also can carry out effectual fixed to crooked unit piece, wraps up the plastic body with the aluminum alloy, and the wire is left to the bottom, and 13mm above the clamping part adopt epoxy to wrap up, and this part and top expose 3mm and be crooked unit piece vibrations part. The part is a movable part, so that the replacement is convenient.
The bent element transmitting end lead 5 is punched and led out through the pressure chamber upper cover 19 and sealed by an O-shaped ring and a steel hoop head, the thermocouple and the bent element receiving end lead 13 are led out through a channel formed in the pressure chamber base 17, and the outlet is sealed by the O-shaped ring and the steel hoop head.
The pressure chamber is placed on a loading frame, which is an existing product. The thermocouple 11 and the heating ring 9 are connected with a temperature controller 25 outside the pressure chamber, and the temperature controller 25 is an existing product. The water inlet 14 and the water outlet 15 are connected to a water inlet and outlet controller 21, and water supply and drainage are controlled by the water inlet and outlet controller 21. The bent element transmitting end 7 and the receiving end 12 are respectively connected with a signal amplifier 23 and an oscilloscope 24 through lead wires. The air inlet 4 of the upper cover 19 of the pressure chamber is connected with an air circulating pump 20 to control the suction force of the sample.
The temperature controller 25 sets the temperature, the heating ring 9 heats the sample, the temperature of the sample is measured and fed back by the thermocouple 11, and the temperature control is completed.
The loess structure collapse nondestructive detection device comprises the following steps:
(1) preparing a sample with a certain size, specifically, taking a sample with a required size from a large soil sample taken back in situ by using a cutting ring, placing the soil sample wrapped by the cutting ring in an electric heating ring 9 on a base, covering an upper cover of a pressure chamber, and screwing a bolt to form sealing to finish a sample loading process;
(2) each structure is connected with a computer, namely, the structure is connected with an air inlet, a water inlet and a water outlet, a bent element transmitting end and a bent element receiving end and is connected with the computer;
(3) applying a load to a target load through a loading frame, namely applying the load to historical overlying pressure, applying vertical pressure of 0.1MPa to the sample step by step when a test is started, monitoring the collapse process in real time and keeping stability all the time;
(4) the target temperature is set through a temperature controller, and the stability is always kept in the process of collapse;
(5) connecting a water inlet 14 on the base of the pressure chamber with a water inlet controller by using a pipeline, applying set water pressure to the pressure chamber, and realizing the control of the initial water-containing condition of the soil sample after the water inlet volume is stable; meanwhile, an air inlet of an upper cover of the pressure chamber is connected with an air pressure controller by a pipeline, and set air pressure is applied to the pressure chamber, so that air uniformly acts on the upper surface of the sample through the permeable stone holes;
(6) connecting a bent element transmitting end lead 5 with a signal generator 23, connecting a thermocouple and a bent element receiving end lead 13 with an oscilloscope, and enabling a bent element transmitting end excitation signal to be received by a bent element receiving end and the oscilloscope to form an image on the oscilloscope so as to realize the measurement of the initial small strain shear modulus of the soil body and the nondestructive detection of the initial structure;
(7) changing the water pressure applied to the pressure chamber to simulate the next stage of the collapse process, repeating the step (6) to excite and record the primary bending element signal after the water inlet volume is stable, and realizing the measurement of the small strain shear modulus of the soil body in the collapse stage and the nondestructive detection of the structural collapse;
(8) and (5) repeating the step (7) until the soil sample is saturated, and realizing the determination of the soil body shear modulus at different stages in the total process of the loess structure collapse and the nondestructive detection of the total process of the structure collapse.
And (4) setting different temperatures in the step (4) in each test, and performing nondestructive detection on the loess structure collapse whole process at different temperatures.
According to the scheme, the invention has the following advantages:
(A) the method comprises the following steps of obtaining a sample with a required size from a bulk soil sample retrieved in situ by using a cutting ring, wherein the soil sample in the cutting ring is the same as the original soil sample except for the temperature, and the cutting ring and the soil sample are integrally placed into a pressure chamber for testing during the test and can be regarded as a nondestructive soil sample;
(B) according to the invention, the temperature of the sample is controlled by the electric heating ring, and the thermocouple and the temperature controller are used for carrying out feedback control on the central temperature of the soil sample in real time, so that the soil sample is uniformly heated, the precision can be controlled to +/-1 ℃, the precision is high, the heating is fast, and the temperature influence is considered more accurately;
(C) according to the invention, by introducing the bending element system, the bending element system can be started for detection at any time, the detection can be carried out when the loess is not collapsed, is collapsed by adding water and after the loess is collapsed, the change condition of the small strain shear modulus in the loess collapsing process is measured, and the small strain shear modulus parameter reflects the soil body structure, the structural change of the soil body in the collapsing process can be quantitatively evaluated, and the continuous nondestructive quantitative detection of different stages of the loess structure collapsing overall process is realized;
(D) the bending element part is a moving part, and the bending element sheet is fragile and easy to damage in the use process;
(E) the suction control part and the consolidation stress of the matrix can be monitored in real time by a computer, so that the recording and the control are convenient;
(F) the method has the advantages of reasonable scheme, clear structure and easy operation, and accurately depicts the whole process of the unsaturated soil loess collapsibility by fully considering various factors influencing the loess collapsibility.
The invention fully considers the unsaturated state of the loess in the actual working conditions of engineering construction, disaster prevention and reduction and the like, simultaneously considers the environmental influences of humidity and temperature along with seasonal changes and the possible changes of the overlying load, and provides the multi-factor coupling detection method considering the moisture content, the temperature and the load influence simultaneously in the loess collapsible process.
It will be readily appreciated by those skilled in the art that the above-described preferred embodiments may be freely combined, superimposed, without conflict.
The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Claims (10)
1. A lower loess structure collapse nondestructive testing device under water-heat-force coupling action comprises a pressure chamber, a consolidation box, a loading unit and an electric heating unit, wherein:
the pressure chamber is a closed chamber, the top of the pressure chamber is provided with an air inlet (4) communicated with the inside of the pressure chamber, and the bottom of the pressure chamber is provided with a water inlet (14) and a water outlet (15) communicated with the inside of the consolidation box;
the consolidation box is arranged in the pressure chamber and comprises a pressure plate (6), a permeable stone (10), a cutting ring (8) and a clay plate (16), and the consolidation box comprises:
the pressure plate (6) is superposed on the permeable stone (10) and forms a consolidation box top cover together with the permeable stone (10), the permeable stone (10) is provided with a bent element emission end (7) and extends into the box, and the bent element emission end (7) is sealed with the permeable stone (10);
the cutting ring (8) is arranged below the permeable stone (10) opposite to the permeable stone (10) to form a consolidation box body, and a loess sample is placed in the consolidation box body;
the argil plate (16) is arranged on a pressure chamber base below the cutting ring (8) to form a consolidation box bottom plate, a bending element receiving end (12) is arranged on the argil plate (16) and extends into the box, and the bending element receiving end (12) is sealed with the argil plate (16);
the loading unit is formed by a loading rod (1) penetrating through the top of the pressure chamber and vertically opposite to the pressurizing plate (6), and the loading rod (1) is sealed with the top of the pressure chamber;
the electric heating unit is used for heating the loess sample in the consolidation box body.
2. The detection device according to claim 1, wherein:
a through hole for the bending element transmitting end (7) to pass through is formed in the permeable stone (10), one end of the bending element transmitting end (7) is fixedly installed on the pressurizing plate (6), the other end of the bending element transmitting end passes through the through hole, and epoxy resin is filled in the through hole;
a through hole for the bending element receiving end (12) to pass through is formed in the argil plate (16), one end of the bending element receiving end (12) is fixedly installed at the bottom of the pressure chamber, the other end of the bending element receiving end passes through the through hole, and epoxy resin is filled in the through hole.
3. The detection device according to claim 1, wherein:
the bending element emitting end (7) is mounted on the pressurizing plate (6) through a sealing unit, the sealing unit comprises a fixed shell (28), a fixed body (29) and epoxy resin (27), the fixed shell (28) is of a cylindrical structure with one end being provided with a bottom, the bottom end of the bending element emitting end (7) is fixedly mounted at the bottom of the fixed shell through the fixed body (29), a lead of the bending element emitting end (7) penetrates out of the bottom of the fixed shell, the top end of the bending element emitting end (7) protrudes out of the fixed shell, and the rest space in the fixed shell is filled with the epoxy resin (27); a sealing ring (26) is arranged outside the fixed shell, a through hole for the fixed shell to pass through is formed in the permeable stone (10), and the fixed shell and the through hole are sealed through the sealing ring (26);
the bending element receiving end (12) is arranged at the bottom of the pressure chamber in the same way, and a through hole for the fixed shell to pass through is formed in the clay plate (16);
preferably, the bottom end of the bent element transmitting end (7) is positioned at the fixed body, the length of the fixed body is not more than three quarters of the length of the bent element transmitting end (7), and the length of the top end of the bent element transmitting end (7) protruding out of the fixed shell is 2-3 mm;
the length of the bottom end of the bent element receiving end (12) positioned on the fixed body is no more than three quarters of the length of the bent element receiving end (12), and the length of the top end of the bent element receiving end (12) protruding out of the fixed shell is 2-3 mm;
preferably, the fixing body (29) is made of plastic.
4. The apparatus according to claim 1, further comprising a thermocouple (11) disposed at the bottom of the pressure chamber and centered on the clay plate (16), wherein the thermocouple (11) extends through the clay plate (16) and into the consolidation chamber, and the thermocouple (11) is sealed to the clay plate (16).
5. The detection device according to claim 4, characterized in that the electric heating unit adopts an electric heating ring (9) which is arranged in the pressure chamber at the periphery of the cutting ring (8) and comprises an annular outer shell (9-1) and a heating wire (9-2), the annular outer shell (9-1) is provided with an inner cavity, the heating wire (9-2) is arranged in the inner cavity, the annular outer shell (9-1) is coaxially arranged with the clay plate (16), and the inner diameter of the annular outer shell (9-1) is not smaller than the diameter of the clay plate (16); the lower end of the annular shell (9-1) is hermetically connected with the bottom of the pressure chamber;
preferably, the lower end of the annular shell (9-1) is detachably and hermetically connected with the bottom of the pressure chamber, the lower end of the annular shell (9-1) is provided with a step (9-3), a sealing ring (26) is sleeved on the outer surface of the step (9-3), and the bottom of the pressure chamber is provided with a groove for embedding the step (9-3).
6. The detection device according to any one of claims 1 to 5, wherein the pressure chamber comprises a pressure chamber upper cover (19), an annular side wall and a pressure chamber base (17), the pressure chamber upper cover (19) and the pressure chamber base (17) are connected and fixed at the top and the bottom of the annular side wall through bolts (18), and sealing rings are arranged on the contact surface of the pressure chamber upper cover (19) and the top of the annular side wall and the contact surface of the pressure chamber base (17) and the bottom of the annular side wall;
preferably, the argil plate (16) is arranged on a pressure chamber base (17) and is positioned in the center of the annular side wall, the thermocouple (11) and the bending element receiving end (12) are both arranged on the pressure chamber base (17), and a pore passage through which a lead of the thermocouple (11) and the bending element receiving end (12) passes is arranged on the pressure chamber base (17);
preferably, the water inlet (14) and the water outlet (15) are arranged on a pressure chamber base (17).
7. The detection device according to claim 6, further comprising a gas circulation pump (20), a water inlet and outlet controller (21) and a temperature controller, wherein the gas circulation pump (20) is connected with the gas inlet (4), the water inlet and outlet controller (21) is connected with the water inlet (14) and the water outlet (15), and the electric heating ring (9) and the thermocouple (11) are connected with the temperature controller.
8. The detection device according to claim 1, further comprising a signal generator (23) and an oscilloscope (24), wherein the bent element transmitting terminal (7) is connected with the signal generator (23), and the bent element receiving terminal (12) is connected with the oscilloscope (24).
9. A testing device according to claim 1, further comprising a displacement sensor (3) mounted on the loading rod (1) with its probe in contact with the top of the pressure chamber.
10. A method for nondestructive testing of collapsible loess structure by water-heat-force coupling, which is based on the testing device of any one of claims 1 to 9, and comprises the following steps:
(1) preparing a sample with a certain size, taking the sample with the required size from the bulk soil sample by using a cutting ring for the bulk soil sample taken back in situ, and putting the soil sample wrapped by the cutting ring into a pressure chamber to finish a sample loading process;
(2) the bending element transmitting end and the bending element receiving end are connected with the air inlet, the water inlet and the water outlet;
(3) applying a load to a target load, and monitoring the collapse process in real time;
(4) setting a target temperature, and keeping the temperature stable all the time in the process of collapse;
(5) applying set water pressure to the pressure chamber until the water inlet volume is stable to realize the control of the initial water containing condition of the soil sample, and applying set air pressure to the pressure chamber to enable the air to uniformly act on the upper surface of the sample through the permeable stone holes until the required matrix suction force is achieved;
(6) the bending element transmitting end excites a signal, and the bending element receiving end receives the signal, so that the measurement of the initial small strain shear modulus of the soil body and the nondestructive detection of the initial structure are realized;
(7) changing the water pressure applied to the pressure chamber to simulate the next stage of the collapse process, repeating the step (6) to excite and record the primary bending element signal after the water inlet volume is stable, and realizing the measurement of the small strain shear modulus of the soil body in the collapse stage and the nondestructive detection of the structural collapse;
(8) and (5) repeating the step (7) until the soil sample is saturated, and realizing the determination of the soil body shear modulus at different stages in the total process of the loess structure collapse and the nondestructive detection of the total process of the structure collapse.
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| CN202210448712.4A CN114858616A (en) | 2022-04-27 | 2022-04-27 | Loess structure collapsibility nondestructive test device under water-heat-power coupling |
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| CN202210448712.4A CN114858616A (en) | 2022-04-27 | 2022-04-27 | Loess structure collapsibility nondestructive test device under water-heat-power coupling |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117647443A (en) * | 2024-01-19 | 2024-03-05 | 中国电建集团西北勘测设计研究院有限公司 | Loess hole inner collapse coefficient testing device and method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117647443A (en) * | 2024-01-19 | 2024-03-05 | 中国电建集团西北勘测设计研究院有限公司 | Loess hole inner collapse coefficient testing device and method |
| CN117647443B (en) * | 2024-01-19 | 2024-04-12 | 中国电建集团西北勘测设计研究院有限公司 | Loess hole inner collapse coefficient testing device and method |
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