CN116256250A - Dead weight type direct shear apparatus for testing shear strength of movable floor base plate and test method - Google Patents

Dead weight type direct shear apparatus for testing shear strength of movable floor base plate and test method Download PDF

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CN116256250A
CN116256250A CN202310549625.2A CN202310549625A CN116256250A CN 116256250 A CN116256250 A CN 116256250A CN 202310549625 A CN202310549625 A CN 202310549625A CN 116256250 A CN116256250 A CN 116256250A
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square groove
temperature
shear strength
bottom plate
inclination angle
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CN116256250B (en
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陈继
李媛
张寿红
刘有乾
马殷军
董添春
美启航
赵静毅
侯鑫
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Northwest Institute of Eco Environment and Resources of CAS
China Railway Qinghai Tibet Group Co Ltd
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Northwest Institute of Eco Environment and Resources of CAS
China Railway Qinghai Tibet Group Co Ltd
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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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D21/00—Measuring or testing not otherwise provided for
    • G01D21/02—Measuring two or more variables by means not covered by a single other subclass
    • 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
    • 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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Abstract

The invention relates to a dead weight type direct shear apparatus for testing shear strength of a movable layer bottom plate and a test method. The test bed comprises a bottom plate and an inclined plate; the bottom plate is connected with the inclined plate; the inclined plate is provided with an inclination sensor; the lifting system comprises a portal frame fixed on the bottom plate; the portal frame is symmetrically provided with a group of diagonal braces and a motor; the shearing box comprises a bottom square groove and an upper square groove which are arranged on the inclined plate; an insulation board I is arranged around the bottom square groove; a copper calandria is arranged at the bottom in the bottom square groove, and is connected with a constant temperature groove; temperature sensors are arranged in the bottom square groove and the upper square groove; the front end of the bottom outer wall of the bottom square groove is provided with a displacement sensor; the lower part of the upper square groove is provided with an enclosure structure; an insulation board II is arranged on the outer wall of the upper square groove. The invention has good stability, high precision and high reliability.

Description

Dead weight type direct shear apparatus for testing shear strength of movable floor base plate and test method
Technical Field
The invention relates to the technical field of shear strength parameter testing of a rock-soil slope sliding surface in geological engineering, in particular to a dead weight type direct shear apparatus for testing the shear strength of a movable layer bottom plate and a test method.
Background
The surface soil layer which is seasonally melted in the frozen soil area for many years is called an active layer. Due to global warming, engineering construction and economic development activities of permafrost areas are enhanced, and engineering of a large number of side slope areas is threatened by frozen soil landslide. The shear strength of the base plate interface of the active layer in the permafrost region is a key factor for determining the stability of the frozen soil slope, so that accurate and rapid acquisition of the shear strength parameters of the potential and easily-occurring sliding interface can provide a direct basis for evaluating the stability of the frozen soil slope.
For the soil slope in the non-frozen soil area, the shearing strength parameters of the soil and stone materials at the typical part in the slope can be obtained by adopting a direct shear test method and a ring shear test method, and the stability of the slope is evaluated according to the shearing strength parameters. However, the above test methods all specify the sliding interface in advance, and obtain the shear strength parameter at the specified interface position. For frozen soil, the shear strength parameters of the freeze-thawing interface can be accurately obtained only when the sliding interface appointed in advance is coincident with the freeze-thawing interface. If the freeze-thawing interface position is set in advance in the sampling link, the interface is ensured to coincide with the sliding interface, and at the moment, the interface position is not influenced by freeze-thawing cycle, so that the difference between the interface condition and the natural freeze-thawing interface is larger, and the obtained strength parameter has larger deviation from the actual one. If the frozen sample is melted or the melted soil sample is frozen, the state and the position of the freeze-thawing interface are difficult to control because the section area of the soil sample in the existing test facility is small and the boundary effect is strong, so that the coincidence of the freeze-thawing interface and the appointed sliding interface in the test process is difficult to ensure, and the shear strength parameter of the freeze-thawing interface is difficult to accurately measure. Although the shearing strength parameters can be obtained in a large-scale field direct shear test, the operation of loading, freeze thawing interface control and the like are difficult in the field test, the test period is long, the investment is large, the obtaining parameters are single, and the stability of the frozen soil slope under different conditions is difficult to evaluate. In addition, the freeze-thaw interface has a certain rheology, and its shear strength includes both instantaneous shear strength and long-term shear strength. Therefore, conventional indoor and field test methods cannot develop long-term shear strength parameter tests due to lack of reliable temperature control conditions.
In summary, the current shear test equipment and method are difficult to accurately and rapidly measure the shear strength parameters of the freeze-thawing sliding surfaces, and cannot meet the requirements of current slope stability assessment of frozen soil engineering.
Disclosure of Invention
The invention aims to solve the technical problem of providing the dead weight type direct shear apparatus for testing the shear strength of the movable layer bottom plate, which has good stability, high precision and high reliability.
The invention aims to provide a test method of the dead weight type direct shear apparatus for testing the shear strength of the movable layer bottom plate.
In order to solve the problems, the dead weight type direct shear apparatus for testing the shear strength of the movable layer bottom plate is characterized in that: the dead weight type direct shear apparatus comprises a control/acquisition system connected with a computer, a test bed arranged in a low-temperature laboratory, a lifting system and a shear box; the test bed comprises a bottom plate and an inclined plate; one end of the bottom plate is connected with one end of the inclined plate through a hinge device, and the other end of the inclined plate is provided with a bearing I; an inclination sensor is arranged on the inclined plate; the lifting system comprises a portal frame, wherein the bottom of the portal frame is fixed on the bottom plate; the lower part of the portal frame is symmetrically provided with a group of diagonal braces, and the end parts of the diagonal braces are fixed on the bottom plate; the top of the portal frame is provided with a motor, and a bearing II is arranged on a rotating shaft of the motor; the bearing I is connected with the bearing II through a steel wire rope; the shearing box comprises a bottom square groove which is arranged on the inclined plate and used for containing a soil sample or an ice sample of a simulated frozen soil layer and an upper square groove which is used for containing a soil sample of a simulated movable layer and a rectangular steel block; the periphery in the bottom square groove is provided with an insulation board I with the thickness of 10 cm; the bottom in the bottom square groove is provided with a copper calandria which is connected with a constant temperature groove through a pipeline; temperature sensors are arranged in the bottom square groove and the upper square groove; the front end of the bottom outer wall of the bottom square groove is provided with a displacement sensor; a building envelope is arranged at the lower part of the upper square groove; an insulation board II is arranged on the outer wall of the upper square groove; the motor, the temperature sensor, the displacement sensor and the inclination sensor are respectively connected with the control/acquisition system.
The bottom plate is of a rectangular frame structure welded by profile steel, is fixed on the bottom plate of the low-temperature laboratory through expansion bolts, and is provided with the hinge device at the end part in the length direction.
The inclined plate is an L-shaped steel plate, a vertical steel plate is arranged on the long side of the L shape, and the bearing I is arranged at the end part of the short side; the vertical steel plate is contacted with the bottom square groove and propped against the bottom square groove.
The tilt sensor is provided on the tilt plate adjacent to the hinge means.
The side length of the inner square cross section of the upper square groove is 300-500 mm, and the height is 50-150 mm; the length and width dimensions of the upper square groove are smaller than those of the bottom square groove.
The temperature sensor arranged in the bottom square groove is a frozen soil layer temperature sensor which is respectively arranged at the bottom end, the middle part and the central position of the 1cm position under the potential sliding interface of the bottom square groove.
The temperature sensor arranged in the upper square groove is divided into an interface temperature sensor and a temperature sensor in the simulated active layer; the interface temperature sensor is arranged in the center of the bottom surface of the upper square groove, the length direction of the sensor is parallel to the sliding interface, the bottom surface of the sensor shell is clung to the potential sliding interface, and the sensor lead is led out from the upper side of the simulated active layer soil sample; the temperature sensor in the simulated active layer is arranged at the central position of the surface layer and the middle part of the upper square groove.
The temperature of the constant temperature tank is minus 10 ℃ to plus 10 ℃ and the precision is +/-0.05 ℃.
Environmental temperature control range of the low temperature laboratory: -20 ℃ to +30 ℃ and precision: + -0.5deg.C.
The test method of the dead weight type direct shear apparatus for testing the sliding surface of the movable layer bottom plate is characterized by comprising the following steps of: the method comprises an instantaneous shear strength test method of the sliding surface of the movable layer bottom plate and a long-term shear strength test method of the sliding surface of the movable layer bottom plate;
the method for testing the instantaneous shear strength of the sliding surface of the movable layer bottom plate comprises the following steps:
preparing an active layer soil sample with set water content, and keeping the temperature of the soil sample at 2-3 ℃;
secondly, adjusting the inclined plates to be in a horizontal state, and arranging 10cm heat-insulating plates I around the square groove at the bottom; then filling a soil sample meeting design requirements into the bottom square groove;
if the designed frozen soil layer is pure ice, adding pure water into the bottom square groove, wherein the water surface is slightly lower than the frame height of the bottom square groove; if the frozen soil is frozen soil with different ice contents, adopting crushed ice with the grain diameter not more than 2mm, liquid water with the temperature of 0 ℃ and dry soil sample with the temperature of minus 6 ℃ to minus 7 ℃ to be quickly and uniformly mixed in a low-temperature laboratory with the temperature of minus 6 ℃ to minus 7 ℃ by using an electric mixer according to the set mass ratio;
rapidly filling the mixture into a bottom square groove, compacting and strickling the surface according to the design requirement, synchronously installing a temperature sensor to a designated position, and then adjusting the temperature of a low-temperature laboratory to-20 ℃ until the soil sample in the bottom square groove reaches the required design negative temperature;
opening lowAfter the temperature of the upper part of the temperature laboratory is quickly raised to a normal temperature environment, the upper part square groove is placed in the middle of the bottom square groove, then soil samples obtained in the steps of filling and compacting the upper part square groove are synchronously placed into an interface temperature sensor and a temperature sensor in a simulated movable layer to a designated position according to the requirements of the movable layer, and the weight of the filled soil samples is recordedG 1 The method comprises the steps of carrying out a first treatment on the surface of the After sample loading is completed, the temperature of a low-temperature laboratory is adjusted to minus 20 ℃, a soil sample is quickly frozen until the movable layer reaches the designed negative temperature, and at the moment, heat preservation plates I with the thickness of 10cm are paved around the upper square groove;
fourthly, the temperature of the low-temperature laboratory is adjusted to a positive temperature range of 10-20 ℃, the temperature of the constant-temperature tank is adjusted to-5 ℃, the movable layer is ensured to be heated and melted from top to bottom, and thick-layer underground ice is not melted;
fifthly, when the temperature sensor at the sliding interface reaches 0 ℃, after the movable layer is completely melted, removing the heat-insulating plate I, which is close to the hinging device, in the bottom square groove, and removing the heat-insulating plate II, which is close to the upper square groove, and the enclosure structure, which is close to the lower part;
starting from the horizontal, continuously increasing the angle of the inclined plate through traction of a motor, a bearing I, a bearing II and a steel wire rope until the upper square groove starts to slide, and recording the initial sliding inclination angle of the bottom square groove
Figure SMS_1
The method comprises the steps of carrying out a first treatment on the surface of the After the upper square groove starts to slide, the inclination angle of the inclined plate is slowly reduced until the upper square groove returns to a static state, and the inclination angle of the bottom square groove is recorded>
Figure SMS_2
；
Adjusting the weight of the soil sample of the movable layer in the square groove at the upper partG 2 And repeating the steps to obtain an initial sliding inclination angle
Figure SMS_3
The method comprises the steps of carrying out a first treatment on the surface of the Slowly decreasing the inclination angle of the inclined plate until the upper square groove returns to rest, at which point the inclination angle +.>
Figure SMS_4
；
Adjusting the weight of the soil sample of the movable layer of the upper square grooveG 3 And then repeating the steps to obtain an initial sliding inclination angle
Figure SMS_5
The inclination angle of the inclined plate is slowly reduced until the upper square groove returns to rest, at which point the inclination angle +.>
Figure SMS_6
；
The refrigerating system of the low-temperature laboratory and the refrigerating system of the constant-temperature tank are closed, the inclined plate is returned to a horizontal state, and then the shearing strength direct shear test of the sliding surface of the bottom plate of the movable layer is finished;
calculating the instantaneous shear strength parameter cohesive force of the sliding surface of the movable layer bottom platecInternal friction angle
Figure SMS_7
：
According to the formula of shear strength
Figure SMS_9
It can be seen that: />
Figure SMS_11
，/>
Figure SMS_13
，
Figure SMS_10
Obtain->
Figure SMS_12
The method comprises the steps of carrying out a first treatment on the surface of the Wherein: />
Figure SMS_14
Is the weight of the soil sample of the movable layer; />
Figure SMS_15
Starting a sliding angle for the active layer;cfor cohesiveness, add->
Figure SMS_8
Is an internal friction angle;
according to the following formula
Figure SMS_16
；/>
Figure SMS_17
；
Figure SMS_18
According to any two formulasc、/>
Figure SMS_19
The third formula is carried to verify the accuracy of the data;
calculating a residual shear strength parameter:
after the upper square groove starts sliding, the inclination angle of the inclined plate is slowly reduced until the upper square groove returns to a static state, according to the inclination angle at the moment
Figure SMS_20
Calculating residual shear strength parameter residual cohesion of the sliding surface of the active layer soleplate +.>
Figure SMS_21
Residual internal friction angle->
Figure SMS_22
；
According to the formula of shear strength
Figure SMS_24
It can be seen that: />
Figure SMS_27
，/>
Figure SMS_29
，
Figure SMS_25
Obtain->
Figure SMS_26
The method comprises the steps of carrying out a first treatment on the surface of the Wherein: />
Figure SMS_28
Is the weight of the soil sample of the movable layer; />
Figure SMS_30
Stopping the sliding angle for the movable layer;cfor residual cohesion>
Figure SMS_23
Is the residual internal friction angle;
according to the following formula
Figure SMS_31
；/>
Figure SMS_32
；
Figure SMS_33
Calculating +.>
Figure SMS_34
、/>
Figure SMS_35
The third formula is carried to verify the accuracy of the data;
the long-term shear strength test method for the sliding surface of the movable layer bottom plate comprises the following steps:
(1) instantaneous with the sliding surface of the movable layer bottom plate the method comprises the following steps of (1) carrying out a shear strength test;
(2) starting from the horizontal, adjusting the inclined plate to a set inclination angle in a small-to-large mode; under the condition of a certain inclination angle, if the sliding distance in the appointed time is smaller than a certain standard, the sliding surface of the bottom plate of the movable layer is considered to be stable under the current inclination angle condition; if the sliding surface of the bottom plate of the movable layer slides under the condition of two adjacent inclination angles, the sliding surface of the bottom plate of the movable layer slides under the condition of a larger inclination angle, and the smaller inclination angle is regarded as a long-term creeping inclination angle of the sliding surface of the bottom plate of the movable layer;
(3) repeating the step (2), and adjusting the loading condition of the movable layer to obtain the long-term creep inclination angle of the sliding surface of the bottom plate of the movable layer under different overlying load conditions;
(4) and (3) according to the long-term creep inclination angle and the overlying load obtained by multiple tests, the reference step is a calculation method of the instantaneous shear strength parameter of the sliding surface of the movable layer bottom plate, and the long-term shear strength parameter of the frozen soil sliding surface of the movable layer bottom plate is obtained.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the motor is used for controlling the inclined plate, and the speed can be adjusted according to the requirement, so that the inclined plate drives the shearing box to stably rotate, therefore, the test control has high automation degree and good stability, and the test result is more accurate.
2. The invention adopts displacement, temperature and inclination angle sensors to monitor, and determines the shear strength parameters of the interface through the critical sliding angles under different normal pressures, so that the accuracy and the reliability of test results are higher.
3. The invention can prepare the active layer and the frozen soil layer with different soil textures, initial water content and ice content by adopting static force and layered compaction methods, and is suitable for researching the shear strength parameters of various sliding surfaces.
4. Compared with the indoor direct shear, ring shear and field direct shear tests, the invention has the advantages of large cross section area, small boundary effect, and interfaces affected by freeze thawing cycle, slides along the sliding surface under self weight, so that the stress is uniform, and the shearing surface is not controlled manually, thereby more conforming to the actual situation.
5. By adopting the device and the method, the instantaneous shear strength test of the frozen soil landslide interface can be performed, and the long-term shear strength test of the frozen soil landslide interface under the creep effect can be considered.
Drawings
The following describes the embodiments of the present invention in further detail with reference to the drawings.
Fig. 1 is a schematic structural view of the present invention.
In the figure: 1-a bottom plate; 2-inclined plate; 3-diagonal bracing; 4-a hinge device; 5-a portal frame; 6, a motor; 7-a steel wire rope; 81-bearing I; 82-bearing II; 9-an inclination sensor; 10-a bottom square groove; 111-an insulation board I; 112-an insulation board II; 12-an enclosure; 13-upper square groove; 14-rectangular steel blocks; 15-a bolt; 16-a temperature sensor; 17-a displacement sensor; 18-copper gauntlets; 19-a control/acquisition system; 20-a constant temperature tank; 21-computer.
Detailed Description
As shown in fig. 1, a dead weight type direct shear apparatus for measuring shear strength of an active layer floor includes a control/acquisition system 19 connected to a computer 21, and a test stand, a lifting system and a shear box which are placed in a low temperature laboratory.
The test bed comprises a bottom plate 1 and an inclined plate 2; one end of the bottom plate 1 is connected with one end of the inclined plate 2 through a hinge device 4, and the other end of the inclined plate 2 is provided with a bearing I81; the inclined plate 2 is provided with an inclination sensor 9, and the inclination sensor 9 is used for monitoring and recording the inclination angle of the bottom square groove 10.
The lifting system comprises a portal frame 5 with the bottom fixed on the bottom plate 1; the lower part of the portal frame 5 is symmetrically provided with a group of inclined struts 3 for increasing rigidity, and the end parts of the inclined struts 3 are fixed on the bottom plate 1; the top of the portal frame 5 is provided with a motor 6, and a bearing II 82 is arranged on a rotating shaft of the motor 6; the bearing I81 is connected with the bearing II 82 through the steel wire rope 7. The inclination angle of the inclined plate 2 is controlled by the motor 6, so that the downward sliding load of the upper square groove 13 is increased or reduced, and the shear strength at the sliding interface can be obtained according to the inclination angle of the inclined plate 2 and the load of the upper square groove 13 when the sliding of the movable layer bottom plate interface occurs.
The shear box comprises a bottom square groove 10 which is arranged on the inclined plate 2 and is used for containing soil samples or ice samples of simulated frozen soil layers, and an upper square groove 13 which is used for containing soil samples of simulated movable layers, rectangular steel blocks 14 and other counterweight articles; the heat insulation board I111 with the thickness of 10cm is arranged around the inside of the bottom square groove 10, and the purpose of the heat insulation board I111 is to prevent the frozen soil sample from being excessively influenced by the heat around the bottom square groove 10. The bottom in the bottom square groove 10 is provided with a copper calandria 18, and the copper calandria 18 is connected with a constant temperature groove 20 through a pipeline so as to ensure that the lower part of the bottom square groove 10 is always in a set negative temperature state. Temperature sensors 16 are arranged in the bottom square groove 10 and the upper square groove 13; the front end of the outer wall of the bottom square groove 10 is provided with a displacement sensor 17, so that the sliding displacement of the upper shearing box can be monitored in real time; the lower part of the upper square groove 13 is provided with an enclosure structure 12, and the enclosure structure 12 can prevent direct friction between the upper square groove 13 and the lower frozen soil layer; an insulation board II 112 is arranged on the outer wall of the upper square groove 13, so as to ensure that the movable layer of the upper square groove 13 is heated and melted from top to bottom; the motor 6, the temperature sensor 16, the displacement sensor 17, the tilt sensor 9 are respectively connected to a control/acquisition system 19 and are displayed on a screen by a computer 21.
Wherein: the bottom plate 1 is a rectangular frame structure welded by profile steel, is fixed on a bottom plate of a low-temperature laboratory through expansion bolts, and is provided with a hinge device 4 at the end part in the length direction.
The inclined plate 2 is an L-shaped steel plate, a vertical steel plate is arranged on the long side of the L shape, and the bearing I81 is arranged on the end part of the short side; the vertical steel plate is in contact with and abuts against the bottom square groove 10. The tilting plate 2 can be connected to the base plate 1 by means of a hinge arrangement 4 and rotated by means of it.
The tilt sensor 9 is provided on the tilt plate 2 close to the hinge device 4.
The side length of the inner square cross section of the upper square groove 13 is 300-500 mm, and the height is 50-150 mm; the length-width dimension of the upper square groove 13 is smaller than the length-width dimension of the lower square groove 10.
The temperature sensor 16 arranged in the bottom square groove 10 is a frozen soil layer temperature sensor which is respectively arranged at the bottom end, the middle part and the central position of the 1cm position under the potential sliding interface of the bottom square groove 10.
The temperature sensor 16 provided in the upper square groove 13 is divided into an interface temperature sensor and a simulated active layer temperature sensor; the interface temperature sensor is arranged in the center of the bottom surface of the upper square groove 13, the length direction of the sensor is parallel to the sliding interface, the bottom surface of the sensor shell is clung to the potential sliding interface, and the sensor lead is led out from the upper side of the simulated active layer soil sample; the temperature sensor in the simulated active layer is arranged at the center of the surface layer and the middle part of the upper square groove 13.
The temperature of the constant temperature tank 20 is minus 10 ℃ to plus 10 ℃ and the precision is +/-0.05 ℃.
Environmental temperature control range (wind control) of low temperature laboratory: -20 ℃ to +30 ℃ and precision: + -0.5deg.C.
Vertical loading device: the vertical load is mainly provided by the weight of the soil sample itself and the weight of the rectangular steel block 14 and other counterweight articles fixed by the bolts 15.
The bottom square groove 10 is made of steel, and can simulate pure ice and frozen soil with different ice contents; the upper square groove 13 is made of organic glass and can simulate the thickness of different active layers; the enclosure 12 is a removable plexiglass.
The motor 6 is controlled by a control/acquisition system 19 to ensure that the inclined plate 2 can be in a set inclination condition.
The method comprises an instantaneous shear strength test method of a sliding surface of the movable floor and a long-term shear strength test method of the sliding surface of the movable floor. Wherein:
the method for testing the instantaneous shear strength of the sliding surface of the movable layer bottom plate comprises the following steps:
preparing an active layer soil sample with set water content, and keeping the temperature of the soil sample at 2-3 ℃;
secondly, adjusting the inclined plate 2 to be in a horizontal state, and arranging 10cm heat preservation plates I111 around the bottom square groove 10; then filling a soil sample meeting design requirements into the bottom square groove 10;
if the designed frozen soil layer is pure ice, pure water is added into the bottom square groove 10, and the water surface is slightly lower than the frame height of the bottom square groove 10; if the frozen soil is frozen soil with different ice contents, adopting crushed ice with the grain diameter not more than 2mm, liquid water with the temperature of 0 ℃ and dry soil sample with the temperature of minus 6 ℃ to minus 7 ℃ to be quickly and uniformly mixed in a low-temperature laboratory with the temperature of minus 6 ℃ to minus 7 ℃ by using an electric mixer according to the set mass ratio;
rapidly filling the mixture into the bottom square groove 10, compacting and strickling the surface according to the design requirement, synchronously installing the temperature sensor 16 to a designated position, and then adjusting the temperature of a low-temperature laboratory to-20 ℃ until the soil sample in the bottom square groove 10 reaches the required design negative temperature;
opening the low-temperature laboratory, quickly heating the upper temperature to the normal temperature (5 ℃) by forced ventilation and the like, placing the upper square groove 13 in the middle of the bottom square groove 10, and filling and compacting the upper square groove 13 according to the requirement of an active layerSynchronously placing soil samples (2-3 ℃) obtained in the steps into an interface temperature sensor and a temperature sensor in a simulated active layer to a designated position, and recording the weight of the filled soil samplesG 1 The method comprises the steps of carrying out a first treatment on the surface of the After the sample is filled, the temperature of a low-temperature laboratory is adjusted to minus 20 ℃, the soil sample is quickly frozen until the movable layer reaches the designed negative temperature (-5 ℃ to minus 10 ℃), and at the moment, 10cm thick heat preservation plates I111 are paved around the upper square groove 13;
fourthly, the temperature of the low-temperature laboratory is adjusted to a positive temperature range of 10-20 ℃, the temperature of the constant temperature tank 20 is adjusted to-5 ℃, the movable layer is ensured to be heated and melted from top to bottom, and thick-layer underground ice is not melted;
fifthly, when the temperature sensor at the sliding interface reaches 0 ℃, and the movable layer is completely melted, removing the heat-insulating plate I111, which is close to the hinging device 4, in the bottom square groove 10, removing the heat-insulating plate II 112, which is close to the upper square groove 13, and the enclosure structure 12, which is close to the lower part, so as to prevent direct friction between the upper square groove 13 and the frozen soil layer;
starting from the horizontal, continuously increasing the angle of the inclined plate 2 by traction of the motor 6, the bearing I81, the bearing II 82 and the steel wire rope 7 until the upper square groove 13 starts to slide, and recording the initial sliding inclination angle of the bottom square groove 10
Figure SMS_36
The method comprises the steps of carrying out a first treatment on the surface of the After the upper square groove 13 starts sliding, the inclination angle of the inclined plate 2 is gradually reduced until the upper square groove 13 returns to a standstill, and the inclination angle +.>
Figure SMS_37
；
Adjusting the weight of the soil sample in the upper square groove 13G 2 And repeating the steps to obtain an initial sliding inclination angle
Figure SMS_38
The method comprises the steps of carrying out a first treatment on the surface of the The inclination angle of the inclined plate 2 is slowly reduced until the upper square groove 13 returns to rest, at which point the inclination angle +.>
Figure SMS_39
；
Adjusting the activity of the upper square groove 13Moving layer soil sample weightG 3 And then repeating the steps to obtain an initial sliding inclination angle
Figure SMS_40
The inclination angle of the inclined plate 2 is slowly reduced until the upper square groove 13 comes to rest, at which point the inclination angle +.>
Figure SMS_41
；
The refrigerating system of the low-temperature laboratory and the refrigerating system of the constant temperature tank 20 are closed, the inclined plate 2 is returned to the horizontal state, and then the shearing strength direct shear test of the sliding surface of the bottom plate of the movable layer is finished;
calculating the instantaneous shear strength parameter cohesive force of the sliding surface of the movable layer bottom platecInternal friction angle
Figure SMS_42
：
According to the formula of shear strength
Figure SMS_45
It can be seen that: />
Figure SMS_47
，/>
Figure SMS_49
，
Figure SMS_44
Obtain->
Figure SMS_46
The method comprises the steps of carrying out a first treatment on the surface of the Wherein: />
Figure SMS_48
Is the weight of the soil sample of the movable layer; />
Figure SMS_50
Starting a sliding angle for the active layer;cfor cohesiveness, add->
Figure SMS_43
Is an internal friction angle;
according to the following formula
Figure SMS_51
；/>
Figure SMS_52
；
Figure SMS_53
According to any two formulasc、/>
Figure SMS_54
The third formula is carried to verify the accuracy of the data;
calculating a residual shear strength parameter:
after the upper square groove 13 starts sliding, the inclination angle of the inclined plate 2 is gradually reduced until the upper square groove 13 returns to a standstill, according to the inclination angle at that time
Figure SMS_55
Calculating residual shear strength parameter residual cohesion of the sliding surface of the active layer soleplate +.>
Figure SMS_56
Residual internal friction angle->
Figure SMS_57
。
According to the formula of shear strength
Figure SMS_59
It can be seen that: />
Figure SMS_62
，/>
Figure SMS_64
，
Figure SMS_60
Obtain->
Figure SMS_61
The method comprises the steps of carrying out a first treatment on the surface of the Wherein: />
Figure SMS_63
Is the weight of the soil sample of the movable layer; />
Figure SMS_65
Stopping the sliding angle for the movable layer;cfor residual cohesion>
Figure SMS_58
Is the residual internal friction angle.
According to the following formula
Figure SMS_66
；/>
Figure SMS_67
；
Figure SMS_68
Calculating +.>
Figure SMS_69
、/>
Figure SMS_70
The third formula is taken to verify the accuracy of the data.
The long-term shear strength test method for the sliding surface of the movable layer bottom plate comprises the following steps:
(1) the method comprises the following steps of firstly, carrying out a test method of the instantaneous shear strength of the sliding surface of the bottom plate of the same movable layer;
(2) starting from the horizontal, the inclined plate 2 is adjusted to a set inclination angle from small to large; under the condition of a certain inclination angle, if the sliding distance in the appointed time is smaller than a certain standard, the sliding surface of the bottom plate of the movable layer is considered to be stable under the current inclination angle condition; if the sliding surface of the bottom plate of the movable layer slides under the condition of two adjacent inclination angles, the sliding surface of the bottom plate of the movable layer slides under the condition of a larger inclination angle, and the smaller inclination angle is regarded as a long-term creeping inclination angle of the sliding surface of the bottom plate of the movable layer;
(3) repeating the step (2), and adjusting the loading condition of the movable layer to obtain the long-term creep inclination angle of the sliding surface of the bottom plate of the movable layer under different overlying load conditions;
(4) and (3) according to the long-term creep inclination angle and the overlying load obtained by multiple tests, the reference step is a calculation method of the instantaneous shear strength parameter of the sliding surface of the movable layer bottom plate, and the long-term shear strength parameter of the frozen soil sliding surface of the movable layer bottom plate is obtained.

Claims (10)

1. The utility model provides a dead weight formula direct shear apparatus for testing of activity layer bottom plate shear strength which characterized in that: the dead weight type direct shear apparatus comprises a control/acquisition system (19) connected with a computer (21), a test bed arranged in a low-temperature laboratory, a lifting system and a shear box; the test bed comprises a bottom plate (1) and an inclined plate (2); one end of the bottom plate (1) is connected with one end of the inclined plate (2) through a hinge device (4), and a bearing I (81) is arranged at the other end of the inclined plate (2); an inclination sensor (9) is arranged on the inclined plate (2); the lifting system comprises a portal frame (5) with the bottom fixed on the bottom plate (1); the lower part of the portal frame (5) is symmetrically provided with a group of inclined struts (3), and the end parts of the inclined struts (3) are fixed on the bottom plate (1); the top of the portal frame (5) is provided with a motor (6), and a bearing II (82) is arranged on a rotating shaft of the motor (6); the bearing I (81) is connected with the bearing II (82) through a steel wire rope (7); the shearing box comprises a bottom square groove (10) which is arranged on the inclined plate (2) and is used for containing a soil sample or an ice sample of a simulated frozen soil layer, and an upper square groove (13) which is used for containing a soil sample of a simulated active layer and a rectangular steel block (14); the periphery in the bottom square groove (10) is provided with an insulation board I (111) with the thickness of 10 cm; the bottom in the bottom square groove (10) is provided with a copper calandria (18), and the copper calandria (18) is connected with a constant temperature groove (20) through a pipeline; a temperature sensor (16) is arranged in the bottom square groove (10) and the upper square groove (13); the front end of the outer wall of the bottom square groove (10) is provided with a displacement sensor (17); the lower part of the upper square groove (13) is provided with an enclosure structure (12); an insulation board II (112) is arranged on the outer wall of the upper square groove (13); the motor (6), the temperature sensor (16), the displacement sensor (17) and the inclination sensor (9) are respectively connected with the control/acquisition system (19).
2. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the bottom plate (1) is of a rectangular frame structure welded by profile steel, is fixed on the bottom plate of the low-temperature laboratory through expansion bolts, and is provided with the hinge device (4) at the end part in the length direction.
3. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the inclined plate (2) is an L-shaped steel plate, a vertical steel plate is arranged on the long side of the L shape, and the bearing I (81) is arranged at the end part of the short side; the vertical steel plate is contacted with the bottom square groove (10) and is propped against the bottom square groove.
4. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the inclination sensor (9) is arranged on the inclined plate (2) close to the hinging device (4).
5. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the side length of the inner square cross section of the upper square groove (13) is 300-500 mm, and the height is 50-150 mm; the length and width dimensions of the upper square groove (13) are smaller than those of the bottom square groove (10).
6. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the temperature sensor (16) arranged in the bottom square groove (10) is a frozen soil layer temperature sensor which is respectively arranged at the bottom end, the middle part and the central position of the 1cm position under the potential sliding interface of the bottom square groove (10).
7. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the temperature sensor (16) arranged in the upper square groove (13) is divided into an interface temperature sensor and a temperature sensor in the simulated active layer; the interface temperature sensor is arranged in the center of the bottom surface of the upper square groove (13), the length direction of the sensor is parallel to the sliding interface, the bottom surface of the sensor shell is clung to the potential sliding interface, and the sensor lead is led out from the upper side of the simulated active layer soil sample; the temperature sensor in the simulated active layer is arranged at the central positions of the surface layer and the middle part of the upper square groove (13).
8. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: the temperature of the constant temperature tank (20) is minus 10 ℃ to plus 10 ℃ and the precision is +/-0.05 ℃.
9. The deadweight direct shear apparatus for shear strength testing of an active layer floor as defined in claim 1, wherein: environmental temperature control range of the low temperature laboratory: -20 ℃ to +30 ℃ and precision: + -0.5deg.C.
10. The test method of the dead weight type direct shear apparatus for testing the shear strength of the movable layer bottom plate according to one of claims 1 to 9, is characterized in that: the method comprises an instantaneous shear strength test method of the sliding surface of the movable layer bottom plate and a long-term shear strength test method of the sliding surface of the movable layer bottom plate;
the method for testing the instantaneous shear strength of the sliding surface of the movable layer bottom plate comprises the following steps:
preparing an active layer soil sample with set water content, and keeping the temperature of the soil sample at 2-3 ℃;
secondly, adjusting the inclined plate (2) to be in a horizontal state, and arranging 10cm heat preservation plates I (111) around the bottom square groove (10); then filling a soil sample meeting design requirements into the bottom square groove (10);
if the designed frozen soil layer is pure ice, pure water is added into the bottom square groove (10), and the water surface is slightly lower than the frame height of the bottom square groove (10); if the frozen soil is frozen soil with different ice contents, adopting crushed ice with the grain diameter not more than 2mm, liquid water with the temperature of 0 ℃ and dry soil sample with the temperature of minus 6 ℃ to minus 7 ℃ to be quickly and uniformly mixed in a low-temperature laboratory with the temperature of minus 6 ℃ to minus 7 ℃ by using an electric mixer according to the set mass ratio;
rapidly filling the mixture into a bottom square groove (10), compacting and strickling the surface according to the design requirement, synchronously installing a temperature sensor (16) to a designated position, and then adjusting the temperature of a low-temperature laboratory to-20 ℃ until the soil sample in the bottom square groove (10) reaches the required design negative temperature;
opening a low-temperature laboratory to enable the upper temperature of the low-temperature laboratory to rise to a normal temperature environment rapidly, placing an upper square groove (13) in the middle of a bottom square groove (10), filling and compacting soil samples obtained in the steps of filling and compacting the upper square groove (13) according to the requirements of an active layer, synchronously placing an interface temperature sensor and a temperature sensor in a simulated active layer to a designated position, and recording the weight of filled soil samplesG 1 The method comprises the steps of carrying out a first treatment on the surface of the After sample filling is completed, the temperature of a low-temperature laboratory is adjusted to minus 20 ℃, and a soil sample is quickly frozen until the movable layer reaches the designed negative temperature, and at the moment, heat preservation plates I (111) with the thickness of 10cm are paved around the upper square groove (13);
fourthly, the temperature of the low-temperature laboratory is adjusted to a positive temperature range of 10-20 ℃, the temperature of the constant-temperature tank (20) is adjusted to-5 ℃, the movable layer is ensured to be heated and melted from top to bottom, and thick-layer underground ice is not melted;
fifthly, removing the heat-insulating plate I (111) close to the hinging device (4) in the bottom square groove (10) after the temperature sensor at the sliding interface reaches 0 ℃ and the movable layer is completely melted, and removing the heat-insulating plate II (112) of the upper square groove (13) and the enclosure structure (12) close to the lower part;
starting from the horizontal, continuously increasing the angle of the inclined plate (2) through the traction of the motor (6), the bearing I (81), the bearing II (82) and the steel wire rope (7) until the upper square groove (13) starts to slide, and recording the initial sliding inclination angle of the bottom square groove (10)
Figure QLYQS_1
The method comprises the steps of carrying out a first treatment on the surface of the After the upper square groove (13) starts sliding, the inclination angle of the inclined plate (2) is slowly reduced until the upper square groove (13) returns to a static state, and recording is performedAt this time, the inclination angle of the bottom square groove (10)>
Figure QLYQS_2
；
Adjusting the weight of the soil sample in the movable layer of the upper square groove (13)G 2 And repeating the steps to obtain an initial sliding inclination angle
Figure QLYQS_3
The method comprises the steps of carrying out a first treatment on the surface of the The inclination angle of the inclined plate (2) is slowly reduced until the upper square groove (13) returns to a standstill, at which time the inclination angle +.>
Figure QLYQS_4
；
Adjusting the weight of the soil sample of the movable layer of the upper square groove (13)G 3 And then repeating the steps to obtain an initial sliding inclination angle
Figure QLYQS_5
The inclination angle of the inclined plate (2) is slowly reduced until the upper square groove (13) returns to a standstill, at which time the inclination angle +.>
Figure QLYQS_6
；
The refrigerating system of the low-temperature laboratory and the refrigerating system of the constant-temperature tank (20) are closed, the inclined plate (2) is returned to a horizontal state, and then the shearing strength direct shear test of the sliding surface of the bottom plate of the movable layer is finished;
calculating the instantaneous shear strength parameter cohesive force of the sliding surface of the movable layer bottom platecInternal friction angle
Figure QLYQS_7
：
According to the formula of shear strength
Figure QLYQS_9
It can be seen that: />
Figure QLYQS_11
，/>
Figure QLYQS_13
，/>
Figure QLYQS_10
Obtain->
Figure QLYQS_12
The method comprises the steps of carrying out a first treatment on the surface of the Wherein: />
Figure QLYQS_14
Is the weight of the soil sample of the movable layer; />
Figure QLYQS_15
Starting a sliding angle for the active layer;cfor cohesiveness, add->
Figure QLYQS_8
Is an internal friction angle;
according to the following formula
Figure QLYQS_16
；/>
Figure QLYQS_17
；
Figure QLYQS_18
According to any two formulasc、/>
Figure QLYQS_19
The third formula is carried to verify the accuracy of the data;
calculating a residual shear strength parameter:
after the upper square groove (13) starts sliding, the inclination angle of the inclined plate (2) is gradually reduced until the upper square groove (13) returns to a standstill, according to the inclination angle at that time
Figure QLYQS_20
Calculating active layer floor slideResidual shear Strength parameter of dynamic surface residual cohesion +.>
Figure QLYQS_21
Residual internal friction angle->
Figure QLYQS_22
；
According to the formula of shear strength
Figure QLYQS_25
It can be seen that: />
Figure QLYQS_27
，/>
Figure QLYQS_29
，
Figure QLYQS_24
Obtain->
Figure QLYQS_26
The method comprises the steps of carrying out a first treatment on the surface of the Wherein: />
Figure QLYQS_28
Is the weight of the soil sample of the movable layer; />
Figure QLYQS_30
Stopping the sliding angle for the movable layer;cfor residual cohesion>
Figure QLYQS_23
Is the residual internal friction angle;
according to the following formula
Figure QLYQS_31
；/>
Figure QLYQS_32
；
Figure QLYQS_33
Calculating +.>
Figure QLYQS_34
、/>
Figure QLYQS_35
The third formula is carried to verify the accuracy of the data;
the long-term shear strength test method for the sliding surface of the movable layer bottom plate comprises the following steps:
(1) instantaneous with the sliding surface of the movable layer bottom plate the method comprises the following steps of (1) carrying out a shear strength test;
(2) starting from the horizontal, adjusting the inclined plate (2) to a set inclination angle in a small-to-large manner; under the condition of a certain inclination angle, if the sliding distance in the appointed time is smaller than a certain standard, the sliding surface of the bottom plate of the movable layer is considered to be stable under the current inclination angle condition; if the sliding surface of the bottom plate of the movable layer slides under the condition of two adjacent inclination angles, the sliding surface of the bottom plate of the movable layer slides under the condition of a larger inclination angle, and the smaller inclination angle is regarded as a long-term creeping inclination angle of the sliding surface of the bottom plate of the movable layer;
(3) repeating the step (2), and adjusting the loading condition of the movable layer to obtain the long-term creep inclination angle of the sliding surface of the bottom plate of the movable layer under different overlying load conditions;
(4) and (3) according to the long-term creep inclination angle and the overlying load obtained by multiple tests, the reference step is a calculation method of the instantaneous shear strength parameter of the sliding surface of the movable layer bottom plate, and the long-term shear strength parameter of the frozen soil sliding surface of the movable layer bottom plate is obtained.
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CN104007025A (en) * 2014-05-08 2014-08-27 河海大学 Multifunctional tilt table device used for testing interfacial shear strength characteristics of geotechnical synthetic material
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