CN114414401B - Large shearing instrument for slide belt soil residual strength regeneration test and application - Google Patents
Large shearing instrument for slide belt soil residual strength regeneration test and application Download PDFInfo
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- CN114414401B CN114414401B CN202111547833.6A CN202111547833A CN114414401B CN 114414401 B CN114414401 B CN 114414401B CN 202111547833 A CN202111547833 A CN 202111547833A CN 114414401 B CN114414401 B CN 114414401B
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- 238000010008 shearing Methods 0.000 title claims abstract description 166
- 238000012360 testing method Methods 0.000 title claims abstract description 84
- 239000002689 soil Substances 0.000 title claims abstract description 58
- 230000008929 regeneration Effects 0.000 title claims abstract description 32
- 238000011069 regeneration method Methods 0.000 title claims abstract description 32
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 78
- 238000006073 displacement reaction Methods 0.000 claims abstract description 38
- 238000012544 monitoring process Methods 0.000 claims abstract description 32
- 230000007246 mechanism Effects 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims description 21
- 230000008569 process Effects 0.000 claims description 20
- 238000003825 pressing Methods 0.000 claims description 14
- 230000005059 dormancy Effects 0.000 claims description 10
- 230000001276 controlling effect Effects 0.000 claims description 6
- 230000009471 action Effects 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 230000009467 reduction Effects 0.000 claims description 2
- 238000004088 simulation Methods 0.000 claims description 2
- 238000013461 design Methods 0.000 abstract description 4
- 230000007547 defect Effects 0.000 abstract description 3
- 230000007958 sleep Effects 0.000 description 7
- 230000007423 decrease Effects 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 230000005389 magnetism Effects 0.000 description 3
- 230000008667 sleep stage Effects 0.000 description 3
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000008054 signal transmission Effects 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 238000000418 atomic force spectrum Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007596 consolidation process Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229940029329 intrinsic factor Drugs 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000036544 posture Effects 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000002352 surface water Substances 0.000 description 1
- 230000009974 thixotropic effect Effects 0.000 description 1
- 230000001550 time effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
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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
Abstract
The invention provides a large shear apparatus for a slide belt soil residual strength regeneration test and application thereof, comprising a shear test system, a load system, a monitoring control system, a water inlet and drainage system and a container; the load system is used for loading load on the shear test system; the load system comprises a lifting mechanism, a lifting arm, a telescopic arm horizontally sliding with the lifting arm, a force adding shaft and a pressurizing plate connected with the lower end of the force adding shaft, wherein the lifting mechanism is used for lifting or descending the lifting arm in the vertical direction; the monitoring control system comprises a displacement monitor, a pressure sensor and a computer, wherein the displacement monitor is used for monitoring horizontal displacement of a telescopic force arm and vertical displacement of a lifting arm, and the pressure sensor is arranged on a load acting surface of the load system to the shear test system. The invention adopts a large-scale shearing design, and avoids the defect that the conventional direct shear apparatus cannot shear the sliding belt soil to the residue at one time due to too small unidirectional shearing displacement.
Description
Technical Field
The invention belongs to the technical field of landslide engineering tests, and particularly relates to a shear mechanical test instrument under a linear stress path condition and application thereof.
Background
After sliding along the sliding surface for a long distance, the sliding belt soil of the sliding slope is sheared to a residual stage, and the corresponding shearing strength is reduced to the residual. Therefore, it is generally considered that the residual strength of the slide belt soil is an important parameter for evaluating the stability of the slide and the design of the anti-skid.
Since the three gorges engineering is implemented, the reservoir is periodically reserved and drained, and the old landslide restarting phenomenon is frequently encountered. After the sliding of the landslide with sliding in the geological history period stops, the landslide is stopped by a long-time dormancy, and the landslide is stimulated by external factors (such as the lifting of the water level of a warehouse) to slide along the original sliding surface again in the later period, which is called restarting of the old landslide. It is generally known that the strength of the sliding surface remains the residual strength at the time of restarting the old landslide. However, many scholars find through parameter inversion that when an old landslide is restarted, the corresponding shear strength is often larger than the residual strength, and the phenomenon of regeneration of the residual strength is shown. Some scholars explain the strength regeneration mechanism, consider that the sliding belt soil generates thixotropic hardening, consolidation creep, structural reinforcement and other series processes in the dormant period, is an intrinsic factor for causing strength regeneration, has obvious time effect, and the longer the dormant time is, the higher the regeneration strength is when the landslide is restarted.
The regeneration of the residual strength has important significance for landslide stability and anti-slip design, and the numerical value is determined by adopting a test means. At present, the residual strength regeneration test is mainly carried out by adopting the conventional direct shear test and the ring shear test. The normal practice is that firstly, forward pressure is applied to the shearing face, then a certain shearing rate is adopted to shear the soil body to residual, then shearing force is released to stop shearing, the sample is kept still for a period of time under the condition that the forward pressure is unchanged, so as to simulate the dormancy period of a landslide, the shearing is restarted after the dormancy period expires, and the shearing strength of the sliding face during restarting is measured. But has the disadvantages that: (1) The shearing distance of the conventional direct shear apparatus is small, and an experiment needs to be carried out by adopting a reciprocating shearing mode, wherein the mode has a unidirectional sliding condition of a non-landslide; (2) When the ring shear apparatus is used for the test, the shearing is stopped by releasing the shearing force, but in practice, the shearing force on the sliding surface is still present when the landslide is dormant. It is difficult for the ring shear to simulate the real conditions.
Disclosure of Invention
In order to overcome the defects of the conventional direct shear apparatus and ring shear apparatus in the landslide soil regeneration strength test, the invention aims to provide a novel shear apparatus suitable for the landslide soil residual strength regeneration test by combining the basic characteristics of landslide evolution development. The equipment is matched with a computer servo control system, can make regulation and control instructions to the power component according to monitoring data transmitted in real time, and improves the automation and multifunction level of the instrument. The equipment simultaneously meets the innovative requirements and actual demands of strong lapping property, great engineering significance and the like.
For this purpose, the above object of the present invention is achieved by the following technical solutions:
a large-scale shearing machine for slide belt soil residual strength regeneration test, its characterized in that: the large shearing instrument for the slide belt soil residual strength regeneration test comprises a shearing test system, a load system, a monitoring control system, a water inlet and drainage system and a container;
the shear test system is arranged in the container, and the load system is used for loading the shear test system;
the water inlet and drainage system is used for adding water into the container or draining water;
the load system comprises a lifting mechanism, a lifting arm, a telescopic arm which horizontally and smoothly slides with the lifting arm, a stress application shaft and a pressurizing plate connected with the lower end of the stress application shaft, wherein the lifting mechanism is used for lifting or descending the lifting arm in the vertical direction. The lower part of the free end of the telescopic arm of force is provided with a force-adding shaft and a pressure plate connected with the lower end of the force-adding shaft, and the telescopic arm of force drives the force-adding shaft and the pressure plate arranged at the lower end of the force-adding shaft to load the shear test system under the lifting action of the lifting mechanism.
Meanwhile, the telescopic arm is a driven component, one side of the telescopic arm penetrates into the lifting arm, and the telescopic arm and the lifting arm are in friction-free contact through smooth balls. On the one hand, when the lifting arm descends, the telescopic arm of force can be driven to move downwards together. On the other hand, when the shearing dislocation causes the displacement of the upper disc mould, the telescopic arm of force can be pulled to move horizontally smoothly along the inside of the lifting arm.
The monitoring control system comprises a displacement monitor, a pressure sensor and a computer, wherein the computer is used for controlling the lifting mechanism to lift or descend the lifting arm in the vertical direction, the displacement monitor and the pressure sensor are connected with the computer in a signal manner, the displacement monitor is used for monitoring the horizontal displacement of the telescopic force arm and the vertical displacement of the lifting arm, and the pressure sensor is arranged on a load acting surface of the load system to the shear test system.
The invention can also adopt or combine the following technical proposal when adopting the technical proposal:
as a preferable technical scheme of the invention: the shearing test system comprises an upper disc die, a lower disc die and an upper shearing box and a lower shearing box which are arranged between the upper disc die and the lower disc die, wherein the upper shearing box and the lower shearing box are respectively clamped into the upper disc die and the lower disc die, and the contact surface between the upper shearing box and the lower shearing box forms a certain inclination angle with the horizontal direction; and the upper shearing box and the lower shearing box are filled with sliding belt soil. The inclined shearing surface is arranged to ensure that the normal stress and the shearing stress on the steel plate are decomposed by the vertical resultant force at the upper part of the steel plate. On the one hand, a linear stress path is controlled, and on the other hand, the maintenance of the shear stress of the shear plane in the sleep stage is ensured.
The main functions of the upper disc die and the lower disc die are to load the shearing box and control the shearing angle. Push grooves are respectively arranged in the bottom surface of the upper disc die and the top surface of the lower disc die, and the push grooves are symmetrical and form a certain inclination angle. The inner side wall of the push groove is provided with a telescopic bolt hole.
The upper disc die and the lower disc die with pushing grooves with different inclined angles can be matched, and shearing tests under different shearing angles can be carried out.
A gap with a certain width is reserved between the upper shearing box and the lower shearing box so as to control the formation of shearing surfaces in the test, and correspondingly, the shearing surfaces divide the sliding belt soil sample into a sliding belt soil upper disc and a sliding belt soil lower disc. The upper shearing box and the lower shearing box respectively correspond to the inner pushing grooves of the upper disc mould and the lower disc mould, the sizes of the upper shearing box and the lower shearing box are matched, and the shearing box can be installed in the pushing grooves. The external surface of the shearing box is provided with a telescopic bolt, the telescopic bolt is retracted into the shearing box before the shearing box is installed into the pushing groove, after the shearing box is installed into the pushing groove, the computer sends out an instruction to extend the bolt into a bolt hole in the inner wall of the pushing groove, so that the shearing box is fixedly connected with the pushing groove, and the angle of a shearing surface is controlled by the inclination angle of the pushing groove.
As a preferable technical scheme of the invention: the bottom of the lower disc mould is provided with a support, and the lower end of the support is propped against the inner bottom of the container and fixed.
As a preferable technical scheme of the invention: the top of shear test system is fixed with the bearing plate, bearing plate top has the recess that holds the pressure board, so, the pressure board can down remove the embedding bearing plate recess in to the bearing plate application of pressure for shearing dislocation in-process, upper disc mould can pull the pressure board and take place horizontal displacement component together with the pressure axle and the flexible arm of force of its upper portion.
As a preferable technical scheme of the invention: an electromagnet is arranged in the bearing plate and used for attracting the pressurizing plate in an electrified state. When the sample is loaded before the test, the magnetism of the sample is electrified and started, the upper disc mould is attracted with the pressurizing plate at the upper part of the upper disc mould, the upper disc mould is driven by the lifting arm to rise and fall to a preset position, and a preset space is formed just with the lower disc mould, so that the shearing box containing the sliding soil sample can be loaded into the upper disc mould and the lower disc mould. And after the sample loading is completed, the magnetism of the bearing plate is released after the power is cut off, and then the shearing test stage of fixing the lower disc and moving the upper disc can be started.
As a preferable technical scheme of the invention: the lifting mechanism comprises a stand column, a hydraulic pump, a vertical guide rail and a frequency converter, wherein the hydraulic pump is arranged at the top of the stand column, the vertical guide rail is arranged along the column shaft of the stand column, and the frequency converter is used for regulating and controlling the hydraulic pump to drive the lifting arm to ascend or descend along the vertical guide rail.
The lifting arm support is a driving component, the hollow structure is adopted, the telescopic arm is a driven component, one side of the telescopic arm is penetrated in the lifting arm, and the two components are in friction-free contact. On the one hand, the frequency converter can drive the lifting arm to lift along the vertical guide rail by regulating and controlling the hydraulic pump, and drive the telescopic force arm and the pressurizing shaft connected with the telescopic force arm to lift, so that the pressurizing plate can be used for loading and unloading the bearing plate. On the other hand, when the shearing box is staggered to cause the horizontal displacement component of the upper disc die in the test, the telescopic arm of force can be driven to smoothly move along the inside of the lifting arm, and no mechanical friction resistance is ensured.
As a preferable technical scheme of the invention: the displacement monitor is arranged on a lifter at the monitoring column for raising or lowering the displacement monitor along the monitoring column. Meanwhile, the data is fed back to the computer through the signal transmission cable, so that the displacement control of the computer on the test is realized.
As a preferable technical scheme of the invention: the water inlet and outlet system comprises a water level monitoring scale, a water inlet tap and a water outlet pipe arranged at the bottom of the container, wherein the water level monitoring scale is used for monitoring the corresponding water storage level when the shearing surface restarts to slide in real time, the water outlet pipe is used for adjusting the height of the water level in the container, the water inlet tap is used for injecting water into the groove-type container until the water storage level in the container is over part or all of the sliding surface, and the water storage level is enough to enable the shearing surface to restart to slide due to effective normal stress reduction. After the water level monitoring scale reads the water level when the shearing surface restarts and slides, the experiment is finished, and the drain pipe can be opened to drain the water in the container.
As a preferable technical scheme of the invention: the invention is matched with a computer servo control system, and can monitor the monitoring data fed back by the displacement monitor in real time according to the preset shearing rate, thereby realizing the rate control of the shearing process by timely coordinating the stress state of the shearing surface, and simultaneously, the invention can also be combined with the use of a pressure sensor to start a force control mode in the dormancy and restarting stages.
A second object of the present invention is to provide the use of a large shear apparatus for a slide soil residual strength regeneration test as described above in a slide soil shear test, comprising individual shear stages, such as an initial stage, a peak stage, a residual stage, a sleep stage and a restart stage, and shear plane stress analysis corresponding to the stages.
It is still another object of the present invention to provide the use of the large shearing apparatus for the test for regenerating the residual strength of a slide belt soil as described above for acquiring the regenerated strength of the slide belt soil, and to quantify the friction angle and cohesion of the regenerated strength based on the test measurement results.
Compared with the prior art, the invention has the following beneficial effects:
1) The invention adopts a large-scale shearing design, and avoids the defect that the conventional direct shear apparatus cannot shear the sliding belt soil to the residue at one time due to small unidirectional shearing displacement.
2) The invention adopts the inclined shearing surface to ensure that the shearing surface is automatically acted by shearing stress in the test process, thereby ensuring the existence of the shearing stress in the sleep slip-stopping stage. Whereas conventional ring shears typically cancel shear forces during the rest of the test due to the horizontal annular shear face setting. Therefore, the invention is more in line with the actual situation of shearing force existing in landslide dormancy.
3) The invention adopts the inclined shearing surface arrangement, so that the normal stress and the shearing stress on the shearing surface are decomposed by the vertical resultant force acting on the upper part of the shearing surface, thereby ensuring a linear stress path and having clear mechanical conditions.
4) The invention is arranged by the inclined shearing surface, so that the shearing stress of the shearing surface in the dormancy stage is ensured to be maintained, and the shearing surface sliding is restarted by adopting a water level lifting mode. In principle, the restarting process of reservoir landslide is restored.
5) The invention is matched with a computer servo control system, and can monitor the monitoring data fed back by the displacement monitor in real time according to the preset shear rate, thereby realizing rate control. Meanwhile, the force control mode can be started when necessary by combining the use of the pressure sensor.
6) The invention attaches importance to the influence of mechanical friction resistance of the instrument, adopts two measures to eliminate, firstly controls the gap width between the upper shearing box and the lower shearing box, and avoids the mechanical friction between the shearing boxes during shearing; second, by, for example: smooth ball control flexible arm of force and the smooth removal between the lifting arm ensure that shearing face receives vertical resultant force only.
Drawings
FIG. 1 is a diagram of a large shear apparatus for a slide belt soil residual strength regeneration test provided by the invention;
FIG. 2 is a schematic representation of the direction A-A of FIG. 1;
FIG. 3 is a schematic representation of the B-B direction of FIG. 1;
FIG. 4 is a graphical representation of the direction C-C of FIG. 1;
FIG. 5 is a perspective view of a shear test system;
FIG. 6 is a schematic representation of a shear box and a preform mold containing different shear inclinations;
FIG. 7 is a graphical representation of a shear test stage;
FIG. 8 is a load-displacement graph;
FIG. 9 is a schematic view of the addition and depressurization of water to the shear face;
FIG. 10 is a graphical representation of the linear stress path experienced by the shear plane during the entire test;
FIG. 11 is a schematic view of various shear dip conditions;
FIG. 12 is a graphical representation of determination of the residual strength and regeneration strength of the slide belt soil;
wherein, the device comprises a 1-container right side wall, a 1 a-water level monitoring scale, a 1 b-container left side wall, a 2-water inlet tap, a 3-water level, a 4-upper tray die, a 5-upper tray sliding belt soil, a 6-upper shearing box, a 7-telescopic bolt, an 8-drain pipe, a 9-support, a 10-shearing inclination angle, a 11-lower tray die, a 12-base, a 13-lower shearing box, a 14-shearing surface and a 15-lower tray sliding belt soil,16-upright post, 17-pressure sensor, 18-monitoring post, 19-displacement monitor, 20-lifter, 21-transducer, 21 a-vertical guide rail, 22-computer, 23-hydraulic pump, 24-lifting arm, 24 a-smooth ball, 25-telescopic arm, 26-shear surface subjected to vertical resultant force, 27-force axis, 28-bearing plate, 29-pressing plate, 30-shear surface length, 31-shear surface width, 32-lower plate mold push slot, 32 a-upper plate mold push slot, 33-telescopic bolt hole, 34-gravity W intercept, 35-horizontal dislocation distance, 36-horizontal dislocation of peak position, 37-horizontal dislocation of residual position one, 38-horizontal dislocation of residual stage two, 39-horizontal dislocation of sleep position, 40-vertical force of peak position, 41-vertical force of residual position one, 42-vertical force of residual position two, 43-vertical force of sleep position, 44-vertical force curve of horizontal dislocation distance, 45-water level line, 46-water level H 1 47-the height of the water pressure at point C at the end of the effective shear plane, 48-the water level H 2 49-effective shear of water pressure height at point B at the front end.
Detailed Description
The present invention will be described in detail with reference to the drawings and examples, but the present invention is not limited to the following examples.
The invention provides a large shearing instrument for a slide belt soil residual strength regeneration test, which is structurally shown in figure 1 and mainly comprises five functional parts, namely a shearing part, a hydraulic loading system, a monitoring control system, a water inlet and drainage system and a container. The container is the cell type, settles on base 12, and the functional part of other experimental usefulness is all arranged in the container except computer 22, and computer 22 locates outside the container, can be operated by the experimenter, realizes the automatic control to the experiment. The computer 22 is the core of the monitoring control system, and is connected with a signal transmission cable, can receive real-time data fed back by a pressure sensor, a displacement monitor and the like, and can send real-time instructions to components such as a frequency converter, a bearing plate (with an electromagnet) and the like according to preset target parameters, automatically regulate and control test steps and servo-control test processes.
The bottom part, a lower disc mould 11 is fixed at the bottom of the container through a support 9 and is kept motionless in the test; a drain pipe 8 is provided at the bottom of the vessel and extends through the base 12 to drain the water at the end of the test. The middle part can see that the top surface of the lower disc mould 11 and the bottom surface of the upper disc mould 4 are symmetrical, a certain inclination angle alpha (marked as 10) is arranged, a certain distance is controlled between the two, pushing grooves are respectively formed, a shearing box containing a sliding belt soil sample is just filled in the shearing box, and the shearing box is fixedly connected with the mould through a telescopic bolt 7. Corresponding to the upper and lower disc molds, the shearing boxes are equally divided into an upper shearing box 6 and a lower shearing box 13 which are symmetrical, a slit width is reserved between the upper shearing box 6 and the lower shearing box 13, the formation of a shearing surface 14 can be guided in the test, the shearing angle of the shearing surface 14 is controlled to be alpha (marked as 10), and the shearing surface 14 divides the slide belt soil sample into an upper slide belt soil 5 and a lower slide belt soil 15. The upper part, the top surface of the upper plate mould 4 is provided with a square groove, a groove-shaped bearing plate 28 with an electrically controllable electromagnet is fixedly connected in the groove-shaped bearing plate 28, a pressure sensor 17 is arranged in the bearing plate 28, and when the pressure sensor 17 presses down the embedded groove-shaped bearing plate 28 in the test process, the pressure F applied to the bearing plate 28 by the pressure sensor 29 can be measured. The pressing plate 29 drives the telescopic arm 25 and the stressing shaft 27 to move downwards through the lifting arm 24, so that the pressing plate 29 presses the bearing plate 28. Or before loading, the electromagnet arranged in the bearing plate 28 is started, the electromagnet is attracted by the pressing plate 29, and the upper disc die 4 is pre-positioned under the drive of the lifting arm 24. Meanwhile, the telescopic arm 25 is a driven member, the left side of the telescopic arm penetrates into the hollow lifting arm 24, and smooth balls 24a are arranged between the telescopic arm and the hollow lifting arm to contact with the telescopic arm, so that the telescopic arm 25 can move up and down along with the lifting arm 24 and can also move smoothly along the lifting arm 24 along with the horizontal dislocation of the sample. The left side, stand 16 installs in the container bottom, and the hydraulic pump 23 is erect at the post top, and the column shaft is equipped with vertical guide rail 21a, and lift arm 24 is put on it, can freely go up and down along vertical guide rail 21a under the regulation and control of converter 21. The monitoring column 18 is arranged on the left side in the container, a lifter 20 is arranged on the monitoring column, the displacement monitor 19 can move up and down along the lifter 20, and the horizontal displacement of the telescopic arm 25 and the vertical displacement of the lifting arm 24 are monitored in real time. The periphery is limited by the container wall to form a groove-shaped closed space for water storage. The water inlet tap 2 is arranged on the right side wall 1 of the container, and a water level monitoring scale 1a is marked on the right side wall 1. Opposite the right side wall 1 is a left side wall 1b of the container. In addition, in the shearing test, the shearing surface receives a vertical resultant force G (denoted as 26, the total weight of the upper disc die, the bearing plate, the pressure sensor, the upper shearing box and the slide belt soil upper disc is W, and in the test process, the W and the pressure F applied to the bearing plate by the pressing plate together form a vertical resultant force g=w+f acting on the shearing surface, and the shearing surface angle is α, so that the positive pressure on the shearing surface is g·cos α, and the shearing force is g·sin α.
Fig. 2 is a view in the direction A-A of fig. 1, showing the relationship between the components on the top surface of the upper plate mold 4. The upper plate mold 4, the pressing plate 29 and the bearing plate 28 are all in a strip shape on a plane, and the upper part of the pressing plate 29 is connected with a pressing shaft 27 and is propped against the groove-shaped bearing plate 28 at the lower part of the pressing plate 29.
Fig. 3 is a view in the direction B-B in fig. 1, showing the lower shear box 13 containing a slide belt soil sample loaded in the pushing groove 32 of the lower tray die 11, and the length of the long shearing surface 14 is designated as a (designated as 30) and the width is designated as B (designated as 31).
Fig. 4 is a view in the direction C-C of fig. 1, showing the spatial relationship between the telescopic arm 25 and the lifting arm. The telescopic arm 25 is seen to pass through the hollow lifting arm 24, and smooth balls 24a are arranged between the telescopic arm 25 and the hollow lifting arm 24 to contact the telescopic arm, and the telescopic arm 25 can move smoothly along the inside of the lifting arm 24.
Fig. 5 is a perspective view of the shear test system showing the positional relationship between the shear box and the mold push groove after loading of the sample is completed. It will be seen that the shear box may be fitted into the lower shear box 13 and the upper shear box 6 along the push grooves so that they are respectively inserted into the lower disc mould push groove 32 and the upper disc mould push groove 32 a. Above the upper plate mold 4, a pressing plate 29 fixedly connected with a pressing shaft 27 can be abutted against a bearing plate 28, so that the upper plate mold can be loaded and unloaded.
Fig. 6 is a schematic representation of a shear box and a prefabricated mold with different shear inclinations. As can be seen in fig. 6 (a), the shear box is equally divided into symmetrical upper and lower shear boxes 6, 13, between which the slide belt soil sample is packed, leaving a certain slit width to guide the formation of the shear face 14. The side of the shearing box is provided with a telescopic bolt 7 which is retracted into the shearing box before being installed in the pushing groove of the die, and after the shearing box is pushed into the pushing groove of the die, the shearing box can be controlled to extend out and be inserted into a bolt hole 33 on the side of the pushing groove by a computer instruction, so that the shearing box is embedded with the die. Fig. 6 (b) to 6 (d) show prefabricated molds with different shearing inclinations, and it can be seen that the shearing boxes can be put into corresponding mold pushing grooves with different postures, and the pushing grooves are provided with bolt holes 33. When the test is performed, the test can be performed based on different prefabricated dies, so that the research on the regeneration of the residual strength under different shearing angles can be realized.
The following test steps are performed in conjunction with fig. 7 to 12:
1. sample loading
First, a slide belt soil sample was taken as it is, and trimmed to a size suitable for the shear box so that the upper and lower shear boxes can be nested thereon, to form a shear box sample as shown in fig. 6 (a).
And then, selecting a corresponding die to carry out sample loading according to the shearing angle. The electromagnet of the bearing plate 28 of the upper disc mould 4 is started by electric control, so that the pressurizing plate 29 is attracted with the electromagnet, and the lifting arm 24 is started to vertically lift the upper disc mould 4 to a preset height. And then, fixing the lower disc mould 11 on the support 9 to realize the alignment of the upper disc mould and the lower disc mould, and enabling the space between the upper disc mould and the lower disc mould to just allow the shear box to be installed. Then pushing the shear box sample into the groove along the mould pushing groove, regulating and controlling the telescopic bolt 7 on the shear box to be inserted into the bolt hole 33 in the groove, so that the shear box is embedded with the mould. After the sample loading is completed, the magnetism of the bearing plate 28 is released by power failure, the suction force is removed, and the loading and unloading of the bearing plate 28 by the pressing plate 29 can be normally performed, and the shearing test stage of fixing the lower disc and moving the upper disc is performed.
2. Loading shear
After the sample loading is completed, a shear test is performed. The test was carried out by applying a vertical load G26 to the specimen to effect shearing with its shear component G.sin. Alpha. Along the shearing plane.
As shown in fig. 7, the test adopts a shear rate control mode from an initial position to a residual position two, that is, the horizontal displacement component of the telescopic arm 25 (the component is the horizontal displacement component caused by the shear dislocation) is monitored in real time in the loading process, and is fed back to the computer 22 to convert the corresponding shear rate, and the computer 22 reversely regulates and controls the load applied to the shear plane 14 according to the preset shear rate value, so as to ensure that the shear rate caused by the load effect is controlled to be the preset rate in real time, and realize the servo control of the shear rate. Since the shear is kept constant, according to Newton's secondThe law is that the shearing force and the shearing resistance moment on the shearing surface 12 are kept equal to obtain the formula (1), wherein c is the cohesive force, phi is the friction angle, a is the length of the shearing surface, b is the width of the shearing surface, l is the horizontal offset, and alpha is the shearing inclination angle. Analysis of the test mechanics curve features from fig. 8: g26 is composed of the total weight W (34) of the upper disc mold 4, the bearing plate 28, the pressure sensor 17, the upper shear box 6, the upper disc slide belt soil 5 and the force F applied by the pressing plate 29, so that the shear curve 44 in fig. 8 starts with W34; in the process of shearing the initial position to the peak position, the horizontal offset distance l35 is increased to l p 36, the friction parameters c, phi are gradually increased to the peak value c p 、φ p Therefore, from formula (1) and experience, it is suggested that G26 should be increased by G p 40, a step of performing a; in the process of clipping the peak position to the residual position I (namely the residual stage starting position) p 36 to l r1 37, c, phi from c p 、φ p Gradually decrease to a residual value c r 、φ r Therefore, G is known from formula (1) p 40 need to be non-linearly reduced to G r1 41; in the process of continuously cutting the first residual position to the second residual position, l r1 37 to l r2 38, residual value c r 、φ r Is unchanged, therefore G is known from formula (1) r1 41 decreases linearly to G r2 42, judging whether the shearing reaches the residual stage or not according to the characteristics in the test.
After the residues, the residual position II is cut to a dormant position I by decelerating as shown in FIG. 7 r2 38 to l s 39, the process maintains the residual strength (c r 、φ r ) And the shear rate gradually decreases to 0. According to Newton's third law, the process can be represented by formula (2), it can be seen that G r2 42 is continuously reduced to G s 43, at which time the shear is stopped. Then keep G s 43, and to sleep for a long period of time. As shown in FIG. 7, in order to avoid the upper disc slide belt soil from overturning around the lower disc slide belt soil bottom point C during the shearing process, the upper disc slide belt soil midpoint P (the action point of the resultant force G26) cannot be sheared through the point C, and therefore needs to be controlled
3. After dormancy, adding water for restarting
After stopping sliding, keep G s 43 is unchanged for a long time (stop time is selected according to requirements), and sleep simulation is performed on the shearing surface. After the sleep is finished, the sliding is restarted in a water level 45 rising mode.
Fig. 9 shows the case of adding water to the container to cause the upper disc slide belt soil 5 to restart along the shear plane. A, C in the figure are the head and tail marking points of the soil on the lower disc, and the upper part Cheng Ji of the A point is H because the lower disc is fixed A The elevation of the point C is H C . The point B is the front end contact point of the upper disc and the lower disc after the sliding belt soil moves in a staggered way, and the horizontal moving distance between the point B and the point A is l s 39. The effective shear plane is the BC segment, and the shear plane inclination angle is marked as alpha.
The water pressure on the shear plane was calculated in two cases.
Case one: when the water level is high H 1 When 46 does not exceed point B, the effective sliding surface BC segment and the water line are intersected at point O, the OC segment is immersed by water, and the shear surface water pressure is calculated as follows:
the water pressure height at the O point is 0, and the water pressure height at the C point is deltah C 47，Δh C ＝H 1 -H C OC segment length ofThus water pressure U 1 ＝0.5·b·γ w ·Δh C 2 And/sin alpha, b31 is the shear plane width.
And a second case: when the water level is high H 2 When 48 exceeds point B, the effective slide BC segment is immersed in water, and the slide water pressure is calculated as follows:
the horizontal offset between the point B and the point A is l s 39, thus giving the elevation of the B point H B ＝H A -l s Tan α. The water pressure height at the point B is delta h B ＝H 2 -H B The water pressure height at the point C is delta h C ＝H 2 -H C BC segment length ofa30 is the total length of the shearing surface, thus the water pressure U 2 ＝0.5·b·γ w ·(Δh B +Δh c )·(a-l s Cos a), b31 is the shear plane width.
In the water adding process, the change of the water level is monitored in real time, and the water pressure on the effective shear surface BC can be calculated in real time according to the first situation or the second situation. The real-time change value of the effective normal stress sigma' of the shear surface BC in the water adding process can be obtained by dividing the forward pressure G.cos alpha on the effective shear surface BC by the area of the effective shear surface BC after subtracting the water pressure. Since G.cosα is a constant value in the sleep stage, σ' decreases as the water level rises during the water addition. While the shear force g·sinα remains unchanged at this stage.
This step requires the continuous addition of water until the shear surface is restarted.
4. Shear plane effective stress path
The shear plane effective stress path may be obtained by transformation from the test loading curve 44 of fig. 8.
Since the angle of inclination α of the shear surface 14 is fixed, the ratio of the shear stress τ and the effective normal stress σ' on the shear surface during the shearing process (except for the water level 45 rise) is always tan α. Accordingly, a stress path on the shear face 14 during the shearing process can be obtained as shown in fig. 10. It can be seen that: (1) the starting point e starts from the initial stress plane (circular, radius p=w/ab) and rises at an angle α to the horizontal to the peak point f, which corresponds to the starting to peak G in fig. 8 p 40 sections; (2) from point f again, the angle alpha from horizontal drops to a residual point G, which corresponds to peak G in FIG. 8 p 40 to residual G r2 42 segments due to residual phase friction parameter (c r 、φ r ) The G point is unchanged, and thus, as seen in formula (1), includes G in FIG. 8 r1 41 to G r2 A residual shear stage between 42; (3) the g point is declined to rest at an angle alpha with the horizontalSleep point h and sleep for a long time at point h, which segment corresponds to peak G in FIG. 8 r2 42 to G s 43 segments.
After the dormancy is finished, continuously increasing the water level from the point h, reducing the effective normal stress sigma', keeping the shearing stress tau unchanged, and developing a stress path along hj until the shearing surface at the point j restarts shearing.
5. Regeneration intensity parameter acquisition
By using the prefabricated die, respectively selecting different shearing inclination angle conditions (figure 11) to carry out the test, the effective stress path of the whole test process under different shearing inclination angles as shown in figure 12 can be obtained. FIG. 12 shows the shear tilt angle α i 、α i+1 、α i+1 For example, the respective effective stress paths are shown, from which the residual strength parameters of the slide belt soil (friction angle phi can be fitted according to the molar coulomb criterion r Cohesive force c r ) And regeneration strength parameter (friction angle phi) z Cohesive force c z ). Since the residual strength is regenerated during dormancy, the regenerated strength envelope is typically located above the residual strength envelope and the tilt angle is increased.
Parameter control:
in order to ensure that the test is performed normally, the relevant parameters of a (shearing inclination angle), W (total weight of upper disc mould, bearing plate, pressure sensor, upper shearing box and slide belt soil upper disc), a (shearing surface length) and b (shearing surface width) of the experimental instrument need to meet the following conditions:
(1) firstly, in order to ensure that the shearing surface can move in a staggered way, the set shearing inclination angle needs to meet the formula (3);
(2) to ensure that the loading G is increased when clipping from the initial position to the peak position, the parameters need to satisfy equation (4);
(3) to ensure that the shear surface is controlled to stop shearing after the residual stage, and to avoid overturning of the upper shear box around the bottom point C of the lower shear box during shearing, the midpoint P (i.e., the resultant force action point, see FIG. 7) of the upper shear box must not shear past the bottom point C of the lower disc shear box, and therefore the parameters must satisfy equation (5).
α＞φ p (3)
c p 、φ p C is the peak cohesion and peak friction angle r 、φ r For residual cohesion and residual friction angle, l p Sec alpha is the shear displacement at the peak, which is the attribute of the slide belt soil itself, and can be obtained in advance by a conventional direct shear test. And then, according to the formulas (3) to (5), corresponding instrument parameters can be designed to ensure that the regeneration test of the residual strength of the sliding belt soil is developed.
The above detailed description is intended to illustrate the present invention by way of example only and not to limit the invention to the particular embodiments disclosed, but to limit the invention to the precise embodiments disclosed, and any modifications, equivalents, improvements, etc. that fall within the spirit and scope of the invention as defined by the appended claims.
Claims (9)
1. A large-scale shearing machine for slide belt soil residual strength regeneration test, its characterized in that: the large shearing instrument for the slide belt soil residual strength regeneration test comprises a shearing test system, a load system, a monitoring control system, a water inlet and drainage system and a container;
the shear test system is arranged in the container, and the load system is used for loading the shear test system;
the water inlet and drainage system is used for adding water into the container or draining water;
the load system comprises a lifting mechanism, a lifting arm, a telescopic arm horizontally sliding with the lifting arm, a force adding shaft and a pressurizing plate connected with the lower end of the force adding shaft, wherein the lifting mechanism is used for lifting or descending the lifting arm in the vertical direction;
the lower part of the free end of the telescopic arm of force is provided with a force-adding shaft and a pressure plate connected with the lower end of the force-adding shaft, and the telescopic arm of force drives the force-adding shaft and the pressure plate arranged at the lower end of the force-adding shaft to load the shear test system under the lifting action of the lifting mechanism;
the telescopic arm is a driven component, one side of the telescopic arm penetrates into the lifting arm, and the telescopic arm and the lifting arm are in friction-free contact through smooth balls; on one hand, when the lifting arm descends, the telescopic arm of force can be driven to move downwards together, and on the other hand, when the shearing dislocation causes the displacement of the upper disc die, the telescopic arm of force can be pulled to move horizontally smoothly along the inside of the lifting arm;
the monitoring control system comprises a displacement monitor, a pressure sensor and a computer, wherein the computer is used for controlling the lifting mechanism to lift or descend the lifting arm in the vertical direction, the displacement monitor and the pressure sensor are both connected with the computer through signals, the displacement monitor is used for monitoring the horizontal displacement of the telescopic force arm and the vertical displacement of the lifting arm, and the pressure sensor is arranged on a load acting surface of the load system on the shear test system;
the shearing test system comprises an upper disc die, a lower disc die and an upper shearing box and a lower shearing box which are arranged between the upper disc die and the lower disc die, wherein the upper shearing box and the lower shearing box are respectively clamped into the upper disc die and the lower disc die, and the contact surface between the upper shearing box and the lower shearing box forms a certain inclination angle with the horizontal direction; the upper shearing box and the lower shearing box are filled with sliding belt soil, and a gap with a certain width is reserved between the upper shearing box and the lower shearing box so as to control the shearing surface.
2. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 1, wherein: the bottom of the lower disc mould is provided with a support, and the lower end of the support is propped against the inner bottom of the container.
3. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 1, wherein: the top of the shear test system is fixed with a bearing plate, and the top of the bearing plate is provided with a groove for accommodating the bearing plate, so that when shearing dislocation is ensured, the upper disc die can pull the bearing plate pressed into the groove of the bearing plate, and the bearing plate, together with a pressing shaft and a telescopic force arm at the upper part of the bearing plate, generates a horizontal displacement component.
4. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 3, wherein: an electromagnet is arranged in the bearing plate, and can attract the pressurizing plate in an electrified state and is used for pre-positioning the upper disc die before the test starts.
5. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 1, wherein: the lifting mechanism comprises a stand column, a hydraulic pump, a vertical guide rail and a frequency converter, wherein the hydraulic pump is arranged at the top of the stand column, the vertical guide rail is arranged along the column shaft of the stand column, and the frequency converter is used for regulating and controlling the hydraulic pump to drive the lifting arm to ascend or descend along the vertical guide rail.
6. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 1, wherein: the displacement monitor is arranged on a lifter at the monitoring column for raising or lowering the displacement monitor along the monitoring column.
7. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 1, wherein: the water inlet and outlet system comprises a water level monitoring scale, a water inlet tap and a water outlet pipe, wherein the water inlet tap is arranged at the bottom of the container and is used for injecting water into the container, the water level monitoring scale is used for monitoring the water level, and the water outlet pipe is used for adjusting the water level in the container; the water is injected into the container to improve the water level, so that the shearing surface is promoted to restart and slide due to the reduction of effective normal stress, and the high simulation of restarting the old landslide is realized.
8. The large shear apparatus for a slide belt soil residual strength regeneration test according to claim 1, wherein: the monitoring control system can monitor the monitoring data fed back by the displacement monitor in real time according to the preset shearing rate, so that the rate control of the shearing process is realized by timely coordinating the stress state of the shearing surface, and meanwhile, the force control mode can be started in the dormancy and restarting stages by combining the use of the pressure sensor.
9. The use of a large shear apparatus for a slide soil residual strength regeneration test according to claim 1 in a slide soil shear test and regeneration strength acquisition.
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