CN112945754A - System and method for testing shear strength of expansive soil under dry-wet cycle action - Google Patents
System and method for testing shear strength of expansive soil under dry-wet cycle action Download PDFInfo
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- CN112945754A CN112945754A CN202110162268.5A CN202110162268A CN112945754A CN 112945754 A CN112945754 A CN 112945754A CN 202110162268 A CN202110162268 A CN 202110162268A CN 112945754 A CN112945754 A CN 112945754A
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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
- G01N3/24—Investigating strength properties of solid materials by application of mechanical stress by applying steady shearing forces
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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
- G01N3/04—Chucks
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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
- G01N2203/0014—Type of force applied
- G01N2203/0025—Shearing
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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
- G01N2203/04—Chucks, fixtures, jaws, holders or anvils
Abstract
The invention discloses a system and a method for testing the shear strength of expansive soil under the action of dry-wet cycle, wherein the technical scheme is as follows: the device comprises a pressure consolidation device, a pressure regulating device and a water volume measuring device, wherein the pressure regulating device and the water volume measuring device are respectively connected with the pressure consolidation device; the pressure consolidation device comprises a sample chamber, a cover plate and a loading part, wherein the cover plate is arranged on the top of the sample chamber, the loading part is arranged in the sample chamber, after the dry-wet cycle in the sample chamber is completed, the loading part and the cover plate are replaced by a shear strength measuring device, and a shear strength test is carried out through the shear strength measuring device. The invention can replace the pressure consolidation device with a shear strength measuring device, realize the measurement of the normal suction shear strength under the action of the dry-wet cycle of the soil sample, accurately measure the shear strength of the soil body under the action of the dry-wet cycle and supplement the important strength index of the expansive soil.
Description
Technical Field
The invention relates to the technical field of indoor geotechnical tests, in particular to a system and a method for testing the shear strength of expansive soil under the action of dry-wet circulation.
Background
The water absorption volume in the expansive soil is obviously expanded, and the dehydration generates obvious volume shrinkage. Under the action of repeated dry-wet circulation, the cracks of the expansive soil are further increased, the integrity is damaged, the soil body is seriously crushed, and the strength is sharply reduced. In the engineering, a plurality of expansive soil subgrades collapse, side slope instability and the like are caused by dry-wet circulation, and the research on the change of the shear strength of the expansive soil under the action of the dry-wet circulation is related to the damage of the expansive soil to structures and the life and property safety of people, so that a method and a device capable of measuring the change of the shear strength of the expansive soil under the action of the dry-wet circulation are urgently needed.
At present, the shear strength of expansive soil in a dry-wet cycle process is difficult to be measured through a laboratory geotechnical triaxial test system, mainly because the geotechnical triaxial test system requires a soil test piece to be a thin and high cylindrical test piece, but the test piece is difficult to achieve suction balance in the dry-wet cycle process, and the actual working condition is that the soil usually undergoes multiple dry-wet cycles, so the laboratory geotechnical triaxial test system is generally not suitable for the shear strength test of the soil sample under the dry-wet cycle effect.
The volume change curve and soil-water characteristic parameters of the expansive soil under the action of dry-wet circulation generally adopt a pressure plate method, and the method is suitable for flat cylindrical samples with substrate suction force smaller than 1500 kPa. The principle is that a saturated argil plate with a high air intake value is utilized, the matrix suction force of the soil sample is controlled by adopting an axis translation technology, namely, certain air pressure is applied to control the pore water pressure so as to keep the pore water pressure to be zero, the air pressure is the currently applied matrix suction force value, and the body deformation curve and the soil-water characteristic parameters of the soil sample under dry-wet circulation can be tested through a displacement sensor and water discharge. However, the method and the device cannot measure the shear strength of the expansive soil in the dry-wet cycle process, so that an important index reflecting the shear strength of the expansive soil in the dry-wet cycle process is lacked.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a system and a method for testing the shear strength of expansive soil under the action of dry-wet circulation.
In order to achieve the purpose, the invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides a system for testing shear strength of expansive soil under a dry-wet cycle effect, including a pressure consolidation device, a pressure regulating device, and a water volume measuring device, where the pressure regulating device and the water volume measuring device are respectively connected to the pressure consolidation device;
the pressure consolidation device comprises a sample chamber, a cover plate and a loading part, wherein the cover plate is arranged on the top of the sample chamber, the loading part is arranged in the sample chamber, after the dry-wet cycle in the sample chamber is completed, the loading part and the cover plate are replaced by a shear strength measuring device, and a shear strength test is carried out through the shear strength measuring device.
As a further implementation manner, the shear strength measuring device comprises a sleeve, wherein a fixed chuck is installed at one end of the sleeve, a torque transmission shaft is arranged in the sleeve, one end of the torque transmission shaft is connected with a booster, and the other end of the torque transmission shaft is connected with a cross-shaped plate head; the outer side of the sleeve is connected with a sealing cover in a sliding mode, and the sealing cover is connected with a lifting rod.
As a further implementation mode, a probe type humidity sensor is installed below the sealing cover, and a spring clamping piece used for fixing the sealing cover is arranged on the side face of the sleeve.
As a further implementation mode, the fixed chuck is provided with a cylindrical needle, the side surface of the sleeve is provided with a groove, and the sealing cover is connected with the groove in a sliding mode.
As a further implementation manner, a force measuring instrument is arranged above the assistor.
As a further implementation manner, the loading component comprises a first loading shaft and a second loading shaft, wherein one end of the first loading shaft is connected with the supercharging cylinder, and the other end of the first loading shaft is connected with the second loading shaft; the first loading shaft is connected with the pressure sensor, and the second loading shaft is connected with the displacement sensor.
As a further implementation mode, the sample chamber comprises a first base and a second base, wherein a pottery clay plate is arranged above the first base, and a base water storage cavity is formed between the first base and the second base; the second base is arranged above the argil plate, and a consolidation ring for fixing the sample is arranged above the second base.
As a further implementation manner, the pressure regulating device comprises a working condition case and an air compressor, wherein the working condition case is provided with a pressure regulating valve, one end of the pressure regulating valve is connected with the sample chamber through a pipeline, and the other end of the pressure regulating valve is connected with a three-way joint; and the three-way joint is connected with the supercharging cylinder and the air compressor.
As a further implementation manner, the water volume measuring device comprises a measuring cylinder which is respectively communicated with the water inlet and the water outlet of the sample chamber, a gas collecting bottle is connected in a pipeline connected between the water outlet and the measuring cylinder, and the gas collecting bottle is connected with the horizontal measuring tube through a pipeline.
In a second aspect, an embodiment of the present invention further provides a method for testing shear strength of expansive soil under the action of dry-wet cycle, where the method is used for the system, and the method includes:
and (3) a dry-wet cycle process: pre-consolidation is carried out through a pressure consolidation device; after the preconsolidation is finished, the water levels in the burette, the gas collecting bottle and the horizontal burette are readjusted to set scales, and the reading is recorded; adjusting air pressure, keeping the vertical stress in the pre-consolidation process unchanged, recording and adjusting the reading and parameters of an instrument until the vertical displacement and the water volume are not changed obviously any more, and the soil sample reaches a suction balance state; repeating the above process to measure the body variation curve and soil-water characteristic curve under the action of the soil sample dry-wet cycle;
and (3) testing the shear strength process:
after the soil sample is subjected to dry-wet circulation, a loading part and a cover plate in the pressure consolidation device are disassembled and replaced by a shear strength measuring device, a fixing chuck cylindrical needle of the shear strength measuring device is pressed into the sample, and a top cover is matched with a fixing rod of a sample chamber to fix the soil sample, so that the soil sample is ensured not to rotate in a shear test; and pressing the cross-shaped plate head into the sample, starting a booster motor to carry out testing, reading the maximum torque value of the force measuring instrument when the soil sample rotates, and measuring the shear strength of the soil sample after dry and wet cycles.
The beneficial effects of the above-mentioned embodiment of the present invention are as follows:
according to one or more embodiments of the invention, after a pressure plate instrument of a soil-water characteristic curve realizes the dry-wet circulation effect of a soil sample, a loading part and a cover plate in a pressure consolidation device are replaced, so that the current test system realizes the measurement of the shear strength of the expansive soil sample under the dry-wet circulation effect; the device has the advantages of convenient operation process and simple principle method, replaces a method for measuring the soil body strength by sample disassembly, reduces the disturbance to the sample, and simultaneously solves the problem that a pressure plate instrument of a soil-water characteristic curve cannot measure the shear strength.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic diagram of a pressure plate apparatus according to one or more embodiments of the present invention;
FIG. 2 is a schematic view of a shear strength measurement device installation according to one or more embodiments of the present disclosure;
FIG. 3 is a schematic diagram of a shear strength measurement device according to one or more embodiments of the present invention;
wherein, 1, a support frame, 2, a sample chamber, 3, a pressurizing cylinder, 4, a first pressure regulating valve, 5, a first loading shaft, 6, a first base, 7, a second base, 8, a clay plate, 9, a consolidation ring, 10, a permeable stone, 11, a rigid cover plate, 12, a working condition case, 13, a second pressure regulating valve, 14, a three-way joint, 15, an air compressor, 16, a first air inlet, 17, a second air inlet, 18, a first water filling port, 19, a second water filling port, 20, a first measuring cylinder, 21, a second measuring cylinder, 22, a water inlet, 23, a water outlet, 24, a gas collecting bottle, 25, a horizontal measuring cylinder, 26, a pressure sensor, 27, a second loading shaft, 28, a displacement sensor, 29, a gas pressure digital display module, 30, a displacement digital display module, 31, a pressure digital display module, 32, a fixed rod, 33, a top cover, 34, a sleeve, 35, a fixed rod, 36 and a cross plate head, 37. the torque transmission shaft 38, the booster 39, the force measuring instrument 40, the groove 41, the sealing cover 42, the humidity sensor 43, the spring clamping piece 44, the lifting rod 45 and the cylindrical needle.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an", and/or "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof;
for convenience of description, the words "up", "down", "left" and "right" in this application, if any, merely indicate that the directions of movement are consistent with those of the figures themselves, and are not limiting in structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting in this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The terms "mounted", "connected", "fixed", and the like in the present application should be understood broadly, and for example, the terms "mounted", "connected", and "fixed" may be fixedly connected, detachably connected, or integrated; the two components can be connected directly or indirectly through an intermediate medium, or the two components can be connected internally or in an interaction relationship, and the terms can be understood by those skilled in the art according to specific situations.
The first embodiment is as follows:
the embodiment provides a system for testing the shear strength of expansive soil under the action of dry-wet circulation, which comprises a pressure plate instrument and a detachable shear strength measuring device, wherein the pressure plate instrument is used for measuring a soil-water characteristic curve, can realize the flat cylindrical test dry-wet circulation of substrate suction within 1500kPa, and comprises a pressure consolidation device, a pressure regulating device, a water volume measuring device and a data acquisition module, and the pressure regulating device, the water volume measuring device and the data acquisition device are respectively connected with the pressure consolidation device; and after the soil sample completes the dry-wet cycle, disassembling a loading part and a cover plate in the pressure consolidation device and replacing the loading part and the cover plate with a shear strength measuring device.
Further, the pressure consolidation device comprises a support frame 1, a sample chamber 2, a pressurization cylinder 3, a first loading shaft 5 and a second loading shaft 27, wherein the pressurization cylinder 3 is installed above the support frame 1, the first loading shaft 5 is arranged inside the support frame 1 and connected with the pressurization cylinder 3, a pressure sensor 26 is connected between the second loading shaft 27 and the first loading shaft 5, and the sample chamber 2 is fixed on the bottom surface of the support frame 1.
The booster cylinder 3 is connected with a pressure regulating device through a pipeline, the booster cylinder 3 is provided with a regulating valve 4, and the loading shaft 15 is controlled by compressed air and the first pressure regulating valve 4 to axially load the sample.
Furthermore, the sample chamber 2 comprises a first base 6, a second base 7, a pottery clay plate 8, a consolidation ring 9, a fixing rod 32 and a cover plate, wherein the first base 6 is provided with a groove for placing the pottery clay plate 8, and a base water storage cavity is formed between the pottery clay plate 8 and the first base 6 and used for collecting water extruded by the test soil sample.
The second base 7 is arranged above the argil plate 8 and connected with the first base 6, and a sealing rubber pad is arranged between the second base 7 and the argil plate 8. In the present embodiment, the second mount 7 is connected to the first mount 6 by bolts; it is understood that in other embodiments, the second base 7 and the first base 6 may be connected in other manners.
The fixing ring 9 is arranged above the second base 7 and used for fixing the sample at the central position of the sample chamber 2; in the test process, a permeable stone 10 and a rigid cover plate 11 are covered above the sample; the first base 6 is connected with the cover plate through a plurality of fixing rods 32.
Further, the pressure regulating device comprises a working condition case 12 and an air compressor 15, wherein the working condition case 12 is provided with an air pressure digital display module 29, a displacement digital display module 30 and a pressure digital display module 31; a second pressure regulating valve 13 is installed on the working condition case 12, one end of the second pressure regulating valve 13 is connected with the sample chamber 2 through a pipeline, and the pipeline is connected with a gas pressure digital display module 29; the other end of the second pressure regulating valve 13 is connected with a three-way joint 14. Two corresponding mounting ports of the three-way joint 14 are respectively connected with the booster cylinder 3 and the air compressor 15.
The side surface of the sample chamber 2 is provided with a first air inlet 16, and the first air inlet 16 is connected with a second pressure regulating valve 13 through a pipeline. The booster cylinder 3 is provided with a second air inlet 17, and the second air inlet 17 is connected with the three-way joint 14 through a pipeline. The second pressure regulating valve 13 is used for controlling the air pressure in the sample chamber 2, the air pressure is provided by an external air compressor 15, and the sample chamber 2 and the booster cylinder 3 are respectively pressurized from a first air inlet hole 16 and a second air inlet hole 17 through a three-way joint 14.
Further, the water volume measuring device comprises a first measuring cylinder 20, a second measuring cylinder 21, a gas collecting bottle 24 and a horizontal measuring tube 25, wherein a water inlet 22 is formed in one side of the bottom of the sample chamber 2, and a water outlet 23 is formed in the other side of the bottom of the sample chamber; the water inlet 22 is connected with a first measuring cylinder 20 through a pipeline, and a first water filling port 18 is arranged at the top of the first measuring cylinder 20; the water outlet 23 is connected with a second measuring cylinder 21 through a pipeline, and a second water filling port 19 is arranged at the top of the second measuring cylinder 21.
The pipeline connected with the first measuring cylinder 20, the second measuring cylinder 21, the water inlet 22, the water outlet 23 and the horizontal measuring tube 25 and the upper part of the gas collecting bottle are respectively provided with a valve, and the functions of saturating a pottery clay plate, measuring the water extruded by a soil sample, removing bubbles generated by a water volume measuring device and the like can be realized by adjusting the valves.
Further, the data acquisition system comprises a pressure sensor 26 fixed on the first loading shaft 5 and a displacement sensor 28 fixed on the second loading shaft 27, wherein the pressure sensor 26 is connected with a pressure digital display module 31, and the displacement sensor 28 is connected with a displacement digital display module 30.
Further, as shown in fig. 2 and 3, the shear strength measuring device comprises a top cover 33, a sleeve 34, a fixed chuck 35, a cross head 36, a torque transmission shaft 37, a force adder 38, a force measuring instrument 39, a sealing cover 41 and a lifting rod 44, wherein the top cover 33 is matched with the fixed rod 32 of the sample chamber 2, and a through hole for the fixed rod 32 to pass through is formed in the position, close to the edge, of the top cover 33; the center of the top cover 33 is provided with a center hole.
The sleeve 34 penetrates through the center hole of the top cover 33, the upper part of the sleeve 34 is fixedly welded with the top cover 33, the lower part of the sleeve is fixedly welded with the fixed chuck 35, and the fixed chuck 35 is provided with a cylindrical needle 45 for fixing a sample. The inner cavity of the sleeve 34 is penetrated by a torque transmission shaft 37, one end of the torque transmission shaft 37 is connected with the cross head 36, the other end is connected with a booster 38, and the booster 38 is used for driving the cross head 36.
A force measuring instrument 39 is arranged above the force multiplier 38, and can currently apply a torque to the test specimen. The surface of the sleeve 34 is provided with a groove 40, and the groove 40 is arranged along the height direction of the sleeve 34 and is used as a sliding track of the sealing cover 41. The sealing cover 41 is sleeved outside the sleeve 34 and is connected with the sleeve 34 in a sliding manner through the groove 40; the sealing cover 41 is circumferentially connected with a lifting rod 44, and the lifting rod 44 is perpendicular to the sealing cover 41.
In this embodiment, the lifting rod 44 is L-shaped, and has a long end parallel to the axial direction of the sleeve 34 and a short end perpendicular to the axial direction of the sleeve 34 and located above the top cover 33. The probe type humidity sensor 42 is fixed below the sealing cover 41, and the spring clamping piece 43 is arranged on the side surface of the sleeve 34, so that the sealing cover 41 and the sleeve 34 can be fixed through the spring clamping piece 43 when the sealing cover 41 is pulled.
When the water content is measured, the cylindrical needle 45 of the fixed chuck 35 is pressed into the periphery of the sample to fix the sample, the probe-type humidity sensor 42 penetrates through the sealing cover 41 and the small hole of the fixed chuck 35 to be pressed into the sample, the measurement data can be read, after the measurement is finished, the sealing cover 41 is pulled by the pull rod 44 to be fixed on the sleeve 34 through the spring clamping piece 43, the cross plate head 36 is pressed into the sample, and the booster 38 is started to start the measurement.
Example two:
the embodiment provides a method for testing the shear strength of expansive soil under the action of dry and wet cycles, and the system of the embodiment one comprises a dry and wet cycle process and a shear strength testing process, specifically:
and (3) a dry-wet cycle process:
preparing a saturated sample by adopting a standard GBT 50123-1999 of geotechnical test method, and starting pre-consolidation through a pressure consolidation device; after the preconsolidation is finished, the water levels in the measuring cylinder, the gas collecting bottle and the horizontal measuring tube are readjusted to the marked scales, and the reading of the measuring tube is recorded.
And (3) rotating the pressure regulating valve to regulate the air pressure to a required substrate suction value, directly displaying the added air pressure value on an air pressure digital display, keeping the vertical stress of the preconsolidation process unchanged, recording and regulating the reading and parameters of an instrument until the vertical displacement and the water volume are not changed obviously any more, and enabling the soil sample to reach a suction balance state.
The above process is repeated to measure the body variation curve and soil-water characteristic curve under the action of the soil sample dry-wet cycle.
And (3) testing the shear strength process:
and after the soil sample completes the dry-wet cycle, the pressure consolidation device is disassembled, and the shear strength measurement device is replaced. Inside shear strength measuring device's fixed chuck columnar needle impressed the sample, and the dead lever cooperation of top cap and sample room is fixed with the soil sample, guarantees that the soil sample does not take place to rotate among the shear test.
The probe-type humidity sensor is pressed into a sample through the small hole of the slidable sealing cover and the fixed chuck, the water content of the sample is read after the reading is stable, and the current suction force of the sample can be obtained by using the measured water content by adopting a soil-water characteristic curve expression.
Wherein, the expression of the soil-water characteristic curve is as follows:
in the formula: a. b and c are fitting parameters, a is a soil property parameter of an air inlet value function, b is a soil property parameter of a water outflow rate function in the soil when the suction force of the matrix exceeds the air inlet value of the soil, and c is a soil property parameter of a residual water content function; Ψ is the substrate suction, ΨrSuction of the substrate, theta, corresponding to the residual moisture contentwIs the volume water content, thetasIs the saturated volume water content.
After the water content is measured, the lifting rod is lifted upwards to drive the sealing cover to pull out the probe type humidity sensor; the spring clamping piece is popped out to fix the sealing cover when the lifting height of the sealing cover is higher than that of the spring clamping piece.
The cross head is pressed into the sample to start the booster motor, and the dynamometer reads the maximum torque value T of the soil sample during rotationmax. In the embodiment, the shear strength (tau) of the soil is described by adopting a soil mechanics formulav) And maximum torsion (T)max) The relationship of (1):
the crosshead design used standard dimensions according to ASTM D4648 specification, D-H-12.7 mm. Thus, according to the measured maximum torque value TmaxObtaining the shear strength tau at the current suctionv。
In the embodiment, after the pressure plate instrument of the soil-water characteristic curve realizes the dry-wet circulation action of the soil sample, the shear strength measuring device is used for replacing the pressure consolidation device, so that the current testing system realizes the measurement of the shear strength of the expansive soil sample under the dry-wet circulation action, the operation process is convenient, the principle and the method are simple, the method for measuring the soil body strength by sample disassembly is replaced, the disturbance to the sample is reduced, and the problem that the pressure plate instrument of the soil-water characteristic curve cannot measure the shear strength is solved.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. A system for testing the shear strength of expansive soil under the action of dry-wet circulation is characterized by comprising a pressure consolidation device, a pressure regulating device and a water volume measuring device, wherein the pressure regulating device and the water volume measuring device are respectively connected with the pressure consolidation device;
the pressure consolidation device comprises a sample chamber, a cover plate and a loading part, wherein the cover plate is arranged on the top of the sample chamber, the loading part is arranged in the sample chamber, after the dry-wet cycle in the sample chamber is completed, the loading part and the cover plate are replaced by a shear strength measuring device, and a shear strength test is carried out through the shear strength measuring device.
2. The system for testing the shear strength of expansive soil under the action of the dry-wet cycle of the expansive soil as claimed in claim 1, wherein the shear strength measuring device comprises a sleeve, a fixed chuck is arranged at one end of the sleeve, a torque transmission shaft is arranged in the sleeve, one end of the torque transmission shaft is connected with a booster, and the other end of the torque transmission shaft is connected with the cross head; the outer side of the sleeve is connected with a sealing cover in a sliding mode, and the sealing cover is connected with a lifting rod.
3. The system for testing the shear strength of expansive soil under the action of dry and wet cycles as claimed in claim 2, wherein a probe-type humidity sensor is installed below the sealing cover, and a spring clamping piece for fixing the sealing cover is arranged on the side surface of the sleeve.
4. The system for testing the shear strength of expansive soil under the action of dry and wet cycles as claimed in claim 2, wherein the fixed chuck is provided with a cylindrical needle, the side surface of the sleeve is provided with a groove, and the sealing cover is in sliding connection with the groove.
5. The system for testing the shear strength of expansive soil under the action of the dry-wet cycle as claimed in claim 2, wherein a load cell is arranged above the assistor.
6. The system for testing the shear strength of the expansive soil under the action of the dry-wet cycle of the expansive soil as claimed in claim 1, wherein the loading component comprises a first loading shaft and a second loading shaft, one end of the first loading shaft is connected with the pressurization cylinder, and the other end of the first loading shaft is connected with the second loading shaft; the first loading shaft is connected with the pressure sensor, and the second loading shaft is connected with the displacement sensor.
7. The system for testing the shear strength of expansive soil under the action of the dry-wet cycle of claim 1, wherein the sample chamber comprises a first base and a second base, a pottery clay plate is arranged above the first base, and a base water storage cavity is formed between the first base and the pottery clay plate; the second base is arranged above the argil plate, and a consolidation ring for fixing the sample is arranged above the second base.
8. The system for testing the shear strength of the expansive soil under the action of the dry-wet cycle of the expansive soil as claimed in claim 6, wherein the pressure regulating device comprises an operating condition case and an air compressor, the operating condition case is provided with a pressure regulating valve, one end of the pressure regulating valve is connected with the sample chamber through a pipeline, and the other end of the pressure regulating valve is connected with the three-way joint; and the three-way joint is connected with the supercharging cylinder and the air compressor.
9. The system for testing the shear strength of expansive soil under the action of the dry-wet cycle of claim 1, wherein the water volume measuring device comprises a measuring cylinder which is respectively communicated with a water inlet and a water outlet of the sample chamber, and a gas collecting bottle is connected in a pipeline connected between the water outlet and the measuring cylinder and is connected with the horizontal measuring tube through a pipeline.
10. A method for testing the shear strength of expansive soil under the action of dry and wet cycles, wherein the system of any one of claims 1-9 is used, comprising:
and (3) a dry-wet cycle process: pre-consolidation is carried out through a pressure consolidation device; after the preconsolidation is finished, the water levels in the burette, the gas collecting bottle and the horizontal burette are readjusted to set scales, and the reading is recorded; adjusting air pressure, keeping the vertical stress in the pre-consolidation process unchanged, recording and adjusting the reading and parameters of an instrument until the vertical displacement and the water volume are not changed obviously any more, and the soil sample reaches a suction balance state; repeating the above process to measure the body variation curve and soil-water characteristic curve under the action of the soil sample dry-wet cycle;
and (3) testing the shear strength process:
after the soil sample is subjected to dry-wet circulation, a loading part and a cover plate in the pressure consolidation device are disassembled and replaced by a shear strength measuring device, a fixing chuck cylindrical needle of the shear strength measuring device is pressed into the sample, and a top cover is matched with a fixing rod of a sample chamber to fix the soil sample, so that the soil sample is ensured not to rotate in a shear test; and pressing the cross-shaped plate head into the sample, starting a booster motor to carry out testing, reading the maximum torque value of the force measuring instrument when the soil sample rotates, and measuring the shear strength of the soil sample after dry and wet cycles.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114279818A (en) * | 2021-12-31 | 2022-04-05 | 西南交通大学 | Bidirectional flexible loading and unloading ring shear device and test method thereof |
| CN115452613A (en) * | 2022-10-08 | 2022-12-09 | 青岛理工大学 | Unsaturated soil direct shear apparatus with scouring measurement and control system |
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