Experimental system for determining dense fine-particle soil dilatation area range and use method of experimental system

Abstract

The invention relates to the field of testing or analyzing materials by means of measuring chemical or physical properties of the materials, in particular to an experimental system for determining a shear expansion area range of dense fine-particle soil and a using method of the experimental system. The experimental system for determining the shear expansion area range of the dense fine-particle soil comprises a preparation subsystem (1), a cutting subsystem (2), a measuring subsystem (3) and a control subsystem (4), and is characterized in that the preparation subsystem (1) comprises a suction device (11), a gas-water separation device (12), a preparation pool (13) and the like; the cutting subsystem (2) comprises cutter teeth (21), a tooth holder (22), a force transducer (23) and the like; the measuring subsystem (3) comprises a permeable stone (31), a water pressure sensor (33) and the like; and the control subsystem (4) comprises a data acquisition instrument (41), a data line (42) and a control device (43). The method is close to reality and good in controllability.

Description

Technical Field

[0001] The invention relates to an experimental system for determining the range of the shear expansion zone of dense fine-grained soil and a use method thereof. Background Art

[0002] As the main ship in the dredging industry, the trailing suction dredger plays an important role in various waterway dredging, port construction, and land reclamation projects. However, the bottom of the main ports and port access channels located on the long coastline is complex and changeable, and densely compacted silt and fine sand are often encountered. This type of soil has the characteristics of high density, low compressibility, high strength, and high bearing capacity. It is as hard as "iron plate", so it is commonly known as "iron plate sand". The average particle size range is between 0.02~0.5mm, and the average natural density is between 1.8~1.95g / m 3 The relative density exceeds 2 / 3. In addition to the internal friction angle with an average value greater than 30°, the strength parameter also has an average cohesion of 5~15kPa, which corresponds to its material composition between sand and clay. Therefore, it exhibits the characteristics of high strength and large bearing capacity, and the standard penetration number is generally greater than 30N.

[0003] It is precisely because of the above characteristics of this type of soil that the efficiency of dredging this type of soil by a trailing suction hopper dredger is extremely low and the progress is slow. For example, the "iron plate sand" existing in Huanghua Port in Hebei Province and the Yangtze River Estuary is generally dredged by a trailing suction hopper dredger at a very low concentration, often less than 1.10t / m 3 .

[0004] In response to the above situation, the relevant construction units and design departments proposed the idea of ​​high-pressure water flushing, that is, to open a hole in the middle of the rake teeth, and then use 4~6 bar water flow to assist in breaking the soil, but the effect was minimal.

[0005] Through research, it was found that the reason why "iron plate sand" is difficult to excavate is mainly due to the obvious shear dilatancy of this type of soil. During the rake tooth cutting process, a certain range of shear dilatancy zone is formed on the rake tooth surface. The pore water pressure in the shear dilatancy zone is negative, which leads to an increase in the effective stress of the soil, thereby significantly improving the shear strength of the soil, and then greatly increasing the cutting resistance of the rake teeth. The main reason why high-pressure water flushing is used to assist in the excavation of "iron plate sand" but has little effect is that due to the failure to recognize the existence of the shear dilatancy zone, although flushing holes are set for flushing, water is not injected into the shear dilatancy zone, or water is not injected into the area with the strongest shear dilatancy, so the shear strength of the soil cannot be reduced, and the resistance reduction effect is very limited. Summary of the invention

[0006] In order to overcome the defects of the prior art and provide a soil dilatancy zone testing device which is close to reality and has good controllability, the present invention discloses an experimental system for determining the dilatancy zone range of dense fine-grained soil and a method for using the same.

[0007] The present invention achieves the purpose of the invention through the following technical solutions: An experimental system for determining the shear expansion zone range of dense fine-grained soil includes: a preparation subsystem, a cutting subsystem, a measurement subsystem and a control subsystem. The preparation subsystem is arranged on the ground, the cutting subsystem is arranged on the preparation subsystem, the measurement subsystem is arranged on the cutting subsystem, and the control subsystem is connected to the measurement subsystem. The system is characterized in that: The preparation subsystem includes a suction device, a gas-water separation device, a preparation tank, a supply device, a vibrating compacting device and a leveling device. The preparation subsystem is used to prepare various types of dense fine-grained soils for experiments, including dense fine sand, dense silt sand and dense silt soil. The preparation pool is arranged on the ground, and soil is arranged in the preparation pool. The suction device and the air-water separation device are arranged on one side of the preparation pool, and the supply device is arranged on the other side of the preparation pool. The vibrating and compacting device and the leveling device are arranged above the soil in the preparation pool. The suction device sucks air from the soil in the preparation pool through the air-water separation device, and the air-water separation device separates the water contained in the air sucked by the suction device. The supply device outputs air-free water to the preparation pool, and the vibrating and compacting device vibrates and compacts the soil in the preparation pool, and the leveling device smoothes the surface of the soil in the preparation pool. The cutting subsystem includes cutter teeth, tooth holders, force sensors, cutting connection devices, angle adjustment hydraulic cylinders, height adjustment hydraulic cylinders, trolleys, tracks and traction systems. The cutting subsystem is used for dynamic cutting of soil. The traction system is arranged on both sides of the top of the preparation pool, the track is fixed above the preparation pool, the trolley is movably arranged on the track through the wheels at the bottom, the traction system ties the two ends of the trolley, the top of the cutting connection device and the height adjustment hydraulic cylinder are fixed to the bottom of the trolley in turn, the moving end of the piston rod of the height adjustment hydraulic cylinder is connected to the middle of the cutting connection device, the cylinder body of the angle adjustment hydraulic cylinder is fixed to the front of the cutting connection device, the moving end of the piston rod of the angle adjustment hydraulic cylinder is connected to the front of the cutting connection device, the tooth seat is fixed to the top of the cutting connection device, the cutter teeth and the force sensor are fixed on the tooth seat, and the trolley moves along the track under the traction of the traction system, thereby driving the cutter teeth to linearly cut the soil; The measurement subsystem includes permeable stone, water pressure sensor, silica gel and communication cable. The measurement subsystem is used to measure the pore water pressure at various locations on the interface between the cutter teeth and the soil in real time during soil cutting. The water pressure sensor is arranged in the hole drilled by the blade teeth in the soil and fixed with silica gel. A communication cable is arranged at one end of the water pressure sensor and the communication cable passes through the hole. A permeable stone is arranged at the other end of the water pressure sensor. The upper surface of the permeable stone is flush with the blade teeth. The water body under pressure in the soil is between the lower surface of the permeable stone and the water pressure sensor. The control subsystem includes a data acquisition instrument, a data line and a control device. The control subsystem is used to automatically collect and store the pore water pressure data generated during the soil cutting process. The communication cable at one end of the water pressure sensor is connected to the data acquisition instrument through the communication cable, the force sensor is also connected to the data acquisition instrument through the communication cable, the data acquisition instrument is connected to the control device through the data cable, and the control device is also connected to the cutting subsystem through the data cable. The control device is equipped with a parameter setting module, a cutting control module, an acquisition control module and a data processing module. While automatically storing the pore water pressure data, the data can be transmitted to other electronic devices through the network.

[0008] The experimental system for determining the range of the shear expansion zone of dense fine-grained soil is characterized by: In the preparation subsystem: The suction device includes a vacuum pump, a suction air pipe and a suction valve. The air inlet end of the vacuum pump is connected to the air-water separation device through the suction air pipe, and the suction air pipe is connected in series with the suction valve; The gas-water separation device comprises a separation valve, a gas-water separation tank, a separation gas pipeline and a vacuum gauge. The gas outlet of the gas-water separation tank is connected to the suction gas pipeline, and the gas inlet of the gas-water separation tank is connected to the preparation pool through the separation gas pipeline. Water is collected in the gas-water separation tank, and the air of the soil in the preparation pool is sucked by the vacuum pump and first input into the gas-water separation tank through the separation gas pipeline. The moisture in the air is collected at the lower part of the gas-water separation tank and accumulated into a water body. The air separated from the moisture is discharged by the vacuum pump through the suction gas pipeline. Separation valves are respectively arranged on the upper part and the bottom part of the side of the gas-water separation tank, and the separation valve is also connected in series on the separation gas pipeline. A vacuum gauge is arranged on the top of the gas-water separation tank. The gas-water separation device is used to separate the gas-water mixture extracted by the vacuum pump to avoid damaging the vacuum pump. The preparation pool includes side walls, foundation, gravel, non-woven fabric, filter, sealing membrane, joint, film discharge device and drainage board. The foundation is built on the ground, and the side walls are built around the foundation. The foundation and the side walls are both masonry structures or concrete structures. The inner and outer surfaces of the foundation and the side walls are coated with waterproof layers. The top surface of the foundation and the lower part of the inner side of the side wall are paved with gravel as a drainage and exhaust channel. The top surface of the gravel is paved with non-woven fabric and filter from bottom to top as an anti-filtration layer. The soil used for the experiment is piled on the filter. The top surface of the soil is paved with filter, non-woven fabric, drainage board and sealing membrane from bottom to top, thereby forming a closed space around the soil. The drainage board is connected to the film discharge device through a joint, and the film discharge device is connected to the separation gas transmission pipe. The length of the inner cavity of the preparation pool is not less than 40m. The supply device includes a water delivery pipe, a supply valve and a water tank for still water. The water tank contains still water. The water tank is connected to the preparation pool through a water delivery pipe at the bottom to input the still water into the preparation pool. The water delivery pipe is connected in series with a supply valve to control the start and stop of the delivery of the still water and the water volume. The vibrating compaction device is used to further compact the soil after the soil is sucked and compacted by the vacuum pump, so that the voids inside the soil are reduced and the density of the soil is increased; The leveling device is fixed on the truss of the trolley, and when the trolley moves, it drives the leveling device to level the soil surface.

[0009] The experimental system for determining the range of the shear expansion zone of dense fine-grained soil is characterized by: In the cutting subsystem: The cutter teeth are fixed on the tooth seat, and the force sensor is fixed on the tooth seat through a flange joint. When the cutter teeth cut the soil, the force sensor synchronously measures the cutting resistance; The cutting connection device comprises a cutting connection device, a cutting connection plate, a cutting connection frame and a cutting connection arm, one end of the cutting connection plate is connected to the force sensor through a bolt-nut assembly, the other end of the cutting connection plate is connected to one end of the cutting connection frame through a bolt-nut assembly, the other end of the cutting connection frame is rotatably arranged on one end of the cutting connection arm through a hinge, and the other end of the cutting connection arm is rotatably arranged on the trolley through a hinge; The cylinder body of the angle adjustment hydraulic cylinder is fixed on the cutting connection arm, and the movable end of the piston rod of the angle adjustment hydraulic cylinder is rotatably connected to the cutting connection frame through a hinge, and the cutting connection frame is driven to rotate by the extension and contraction of the piston rod of the angle adjustment hydraulic cylinder to adjust the cutting angle of the cutter teeth; The cylinder body of the height adjustment hydraulic cylinder is fixed at the bottom of the trolley. The movable end of the piston rod of the height adjustment hydraulic cylinder is rotatably connected to the cutting connecting arm through a hinge. The piston rod of the height adjustment hydraulic cylinder drives the cutter teeth to move up and down to adjust the height of the cutter teeth, thereby adjusting the thickness of the soil cut by the cutter teeth. The traction system includes a wire rope, a power system, a traction controller and a frame. The frame is fixed on one side of the preparation tank. The power system and the traction controller are both arranged on the frame. The traction controller is respectively connected to the power system, the angle adjustment hydraulic cylinder and the height adjustment hydraulic cylinder through signal lines. The traction controller is also connected to the control device through signal lines. The wire rope is led out from the power system and tied to both sides of the trolley. The traction controller adjusts the direction and speed of the traction trolley by controlling the power system under the command of the control device.

[0010] The experimental system for determining the range of the shear expansion zone of dense fine-grained soil is characterized by: The power system uses a winch or electric hoist, and the traction controller uses a programmable controller, single-chip microcomputer or microcomputer; The water pressure sensor uses a micro pressure sensor; The control device uses a microcomputer; The control device controls the power system, the angle adjustment hydraulic cylinder and the height adjustment hydraulic cylinder through the traction controller according to the set parameters, so as to control the cutter teeth to reciprocate according to the set parameters to cut the soil. The data acquisition instrument collects the cutting resistance value measured by the force sensor and the pore water pressure value measured by the water pressure sensor in real time according to the set parameters and transmits them to the controller. The controller stores the received cutting resistance value and the pore water pressure value. The controller can also transmit the cutting resistance value and the pore water pressure value to other electronic devices through the network. After the cutting meets the set requirements, the control device controls the power system, the angle adjustment hydraulic cylinder and the height adjustment hydraulic cylinder to stop running and return to the initial position through the traction controller. The control device then processes the received cutting resistance value and the pore water pressure value.

[0011] The method for using the experimental system for determining the range of the shear expansion zone of dense fine-grained soil is characterized by being implemented in the following steps: S1. Soil preparation: Soil is placed in the preparation pool. The air in the soil is sucked by the vacuum pump and first input into the air-water separation tank through the separation air pipe. The moisture in the air is collected at the bottom of the air-water separation tank and accumulated into water. The air separated from the moisture is discharged by the vacuum pump through the suction air pipe. The water tank is connected to the preparation pool through the water pipe at the bottom to input air-free water into the preparation pool. S2. Setting: In the maintenance mode, the control device controls the power system through the traction controller to perform zero-position correction on the trolley and the wire rope respectively. The control device sets the cutting speed of the cutter teeth, the acquisition frequency of the force sensor and the acquisition frequency of the water pressure sensor through the parameter setting module, powers on the inverter of the power system to put the inverter in a ready state, and ensures that the braking and tensioning hydraulics of the traction system work normally. S3. Cutting: The cutting control module of the control device controls the power system, the angle adjustment hydraulic cylinder and the height adjustment hydraulic cylinder respectively through the traction controller. The piston rod of the angle adjustment hydraulic cylinder is extended and retracted to drive the cutting connection frame to rotate, thereby adjusting the cutting angle of the cutter teeth. The piston rod of the height adjustment hydraulic cylinder is extended and retracted to drive the cutter teeth to move up and down to adjust the height of the cutter teeth, thereby adjusting the thickness of the soil cut by the cutter teeth. The trolley moves along the track under the traction of the traction system, thereby driving the cutter teeth to linearly cut the soil at the set cutting speed. S4. Measurement: When the cutter teeth cut the soil, the force sensor synchronously measures the cutting resistance according to the set acquisition frequency, and the water pressure sensor synchronously measures the pore water pressure at various locations on the interface between the cutter teeth and the soil during the soil cutting process according to the set acquisition frequency; S5. Collection: The collection control module of the control device receives and stores the cutting resistance value measured by the force sensor and the pore water pressure value measured by the water pressure sensor through the data acquisition device; S6. Analysis: The data processing module of the control device determines the range of the dilatancy zone according to the received cutting resistance value and pore water pressure value. The specific steps are as follows: First, the positions where the measured pore water pressure is positive are marked with "+" and the negative values ​​are marked with "-". Then, for the areas adjacent to the positive and negative values, difference processing is performed to obtain the positions where the pore water pressure is 0. The positions where the pore water pressure is 0 are then plotted as data points on the tooth surface plane of the cutter tooth. Finally, the points where the pore water pressure is 0 are connected into a line, which is the boundary between the dilatancy zone and the non-dilatancy zone. The area with negative pore water pressure is the final determined dilatancy zone range. S7. Reset: Stop the trolley to stop the cutting of the soil by the blade teeth, and then make the trolley retreat to the initial zero position at the set speed.

[0012] The method for using the experimental system for determining the range of the shear expansion zone of dense fine-grained soil is characterized by: In step S1, the soil to be put into the preparation pool is dug from the excavation construction site, and impurities (such as stones, garbage, branches, etc.) are removed to ensure the uniformity of the soil. The various indicators of the soil put into the preparation pool should be basically consistent with the soil at the excavation construction site; In step S3, the moving speed of the cutter teeth when cutting the soil is not more than 3m / s and the fluctuation range of the moving speed is not more than 5%. When cutting, the first 5m is an acceleration section where the speed increases from zero to the moving speed, and the last 5m is a deceleration section where the speed drops from the moving speed to zero. The section between the acceleration section and the deceleration section is a cutting section of the moving speed, and the length of the cutting section is not less than 30m. In step S5, the collection control module of the control device receives and stores the cutting resistance value measured by the force sensor and the pore water pressure value measured by the water pressure sensor at a frequency of once every 1 mm of movement of the cutter teeth.

[0013] In order to eliminate the dilatancy effect of soil, thereby reducing the shear strength of soil and further reducing the cutting resistance of rake teeth, it is necessary to develop a relevant experimental system to truly reproduce the actual process of rake teeth cutting soil at the construction site. A series of model experiments are carried out through the experimental system to determine the distribution of negative pore water pressure along the tooth surface, and the distribution range of the dilatancy zone along the tooth surface of the rake teeth during soil cutting is determined by the experimental results.

[0014] During the cutting process of dense fine-grained soil under undrained conditions, negative pore water pressure is generated due to the shear expansion of the soil. Therefore, the pore water pressure data automatically stored by the data acquisition instrument are sorted out, and the shear expansion zone range is determined by the area corresponding to the negative pore water pressure measured by each pore water pressure sensor buried on the tooth surface of the cutter.

[0015] Aiming at the common difficulties in the current "iron plate sand" dredging construction, the present invention first proposes a soil preparation subsystem for preparing soil parameters equivalent to those of the on-site soil, so as to restore the on-site construction soil, and various main indicators can reach the indicator range of "iron plate sand"; a cutting subsystem is proposed, which can reproduce the actual situation of rake teeth cutting soil, including cutting speed, cutting angle and cutting thickness, which can be completely consistent with the on-site; a measuring subsystem is proposed, which can measure the pore water pressure value generated in the process of rake teeth cutting soil, and store it in real time, providing a data source for the subsequent determination of shear expansion zone; in addition, a control subsystem is proposed to realize the automatic control of the rake teeth cutting soil process, and its accuracy can be guaranteed.

[0016] The present invention can truly reproduce the actual process of rake teeth cutting soil at a construction site, and conduct a series of model experiments through an experimental system to determine the distribution of negative pore water pressure along the tooth surface. The distribution range of the shear expansion zone along the tooth surface of the rake teeth during soil cutting is determined by the experimental results, further providing a basis for actively replenishing water to the shear expansion zone to reduce the shear expansion effect and thus reduce the cutting resistance of the cutter teeth.

[0017] The present invention is suitable for dense silt and fine sand with a relative density greater than 2 / 3 and a standard penetration number greater than 30N, that is, soil commonly known as "iron plate sand", which will show shear expansion when the soil needs to be cut by rake teeth. After determining the range of the shear expansion zone, one or two high-pressure flushing holes are set near the maximum negative pore water pressure area, and the flushing pressure reaches more than 10 bar. By actively replenishing water to the shear expansion zone, the pore water pressure in the shear expansion zone changes from negative to positive, thereby effectively reducing the effective stress of the soil, and then reducing the cutting resistance of the rake teeth.

[0018] The invention is applicable to dredging engineering and is used to determine the range of the shear expansion zone formed on the surface of the cutter teeth during the dredging of dense fine-grained soil, and provides a basis for actively replenishing water to the shear expansion zone to reduce the shear expansion effect and thus reduce the cutting resistance of the cutter teeth.

[0019] The present invention can simulate different soil types at a construction site and can simulate the actual situation of a prototype cutter tooth cutting a soil body, and can also perform real-time measurement of pore water pressure and real-time collection of experimental data.

[0020] The invention has the following beneficial effects: close to engineering practice, high integration, remote automatic control, real-time display and automatic storage of data. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention, Figure 2 is a schematic diagram of the structure of the preparation subsystem in the present invention, Figure 3 is a schematic diagram of the structure of the suction device in the present invention, Figure 4is a schematic diagram of the structure of the gas-water separation device in the present invention, Figure 5 It is a schematic diagram of the structure of the preparation pool in the present invention, Figure 6 is a schematic diagram of the structure of the supply device in the present invention, Figure 7 is a schematic diagram of the structure of the cutting subsystem in the present invention, Figure 8 is a schematic diagram of the structure of the cutting connection device in the present invention, Fig. 9 is a schematic diagram of the structure of the traction system in the present invention, Fig.10 is a schematic diagram of the structure of the measurement subsystem in the present invention, Fig.11 is a schematic diagram of the control subsystem in the present invention, Fig.12 It is a connection diagram of the control device in the present invention connecting the force sensor, the water pressure sensor, the power system, the angle adjustment hydraulic cylinder and the height adjustment hydraulic cylinder through the data acquisition instrument and the traction controller. Fig.13 is a control flow chart of the traction controller in the present invention, Fig.14 It is a schematic diagram of the shear expansion zone range of the tooth surface determined by the present invention.

[0022] The component names corresponding to the reference numerals are as follows: 1: Prepare subsystem, 11: Suction device, 111: Vacuum pump, 112: Suction gas pipe, 113: Suction valve, 12: Gas-water separation device, 121: Separation valve, 122: Gas-water separation tank, 123: water bodies, 124: Separate the gas pipeline, 125: vacuum gauge, 13: Preparation pool, 131: side wall, 132: Foundation, 133: Gravel, 134: non-woven fabric, 135: filter, 136: Sealing film, 137: connector, 138: Film discharging device, 139: Drainage board, 14: Supply device, 141: Water pipe, 142: Supply valve, 143: Jug, 144: Still water, 15: Vibrating compaction device, 16: Leveling device, 2: Cutting subsystem, 21: Knife teeth, 211: Tooth surface, 22: Gear seat, 23: Force sensor, 24: Cutting connection device, 241: Cutting connecting plate, 242: Cutting connecting frame, 243: Cutting connecting arm, 25: Angle adjustment hydraulic cylinder, 26: Height adjustment hydraulic cylinder, 27: Trolley, 28: Track, 29: Traction system, 291: Wire rope, 292: Power system, 293: Traction controller, 294: rack, 3: Measurement subsystem, 31: Permeable stone, 32: Water bodies, 33: Water pressure sensor, 34:Silica gel, 35: Communication cable, 4: Control subsystem, 41: Data acquisition instrument, 42: Data cable, 43: Control device, 5: Soil. DETAILED DESCRIPTION

[0023] The present invention is further described below by means of specific examples.

[0024] Example 1 An experimental system for determining the range of the shear expansion zone of dense fine-grained soil includes: a preparation subsystem 1, a cutting subsystem 2, a measurement subsystem 3 and a control subsystem 4, such as Figure 1 As shown, the specific structure is: The preparation subsystem 1 is arranged on the ground, the cutting subsystem 2 is arranged on the preparation subsystem 1 , the measurement subsystem 3 is arranged on the cutting subsystem 2 , and the control subsystem 4 is connected to the cutting subsystem 2 .

[0025] Preparation subsystem 1 Figure 2 As shown: the preparation subsystem 1 includes a suction device 11, an air-water separation device 12, a preparation pool 13, a supply device 14, a vibration compaction device 15 and a leveling device 16. The preparation subsystem 1 is used to prepare various types of dense fine-grained soils including dense fine sand, dense silt sand and dense silt soil for experiments.

[0026] A preparation pool 13 is arranged on the ground, and a soil body 5 is arranged in the preparation pool 13. A suction device 11 and an air-water separation device 12 are both arranged on one side of the preparation pool 13, and a supply device 14 is arranged on the other side of the preparation pool 13. A vibrating and compacting device 15 and a leveling device 16 are both arranged above the soil body 5 in the preparation pool 13. The suction device 11 sucks the air of the soil body 5 in the preparation pool 13 through the air-water separation device 12, and the air-water separation device 12 separates the moisture contained in the air sucked out by the suction device 11. The supply device 14 outputs air-free water 144 to the preparation pool 13, the vibrating and compacting device 15 vibrates and compacts the soil body 5 in the preparation pool 13, and the leveling device 16 smoothes the surface of the soil body 5 in the preparation pool 13.

[0027] Suction device 11 such as Figure 3 As shown: the suction device 11 includes a vacuum pump 111, a suction air pipe 112 and a suction valve 113. The air inlet end of the vacuum pump 111 is Figure 3 The IN end of the vacuum pump 111 is connected to the gas-water separation device 12 through the suction gas pipe 112, and the gas outlet end of the vacuum pump 111 is Figure 3 At the OUT end, a suction valve 113 is connected in series on the suction gas pipe 112.

[0028] Gas-water separation device 12 Figure 4 As shown in the figure, the gas-water separation device 12 includes a separation valve 121, a gas-water separation tank 122, a separation gas pipeline 124 and a vacuum gauge 125. The gas outlet of the gas-water separation tank 122 is connected to the suction gas pipeline 112, and the gas inlet of the gas-water separation tank 122 is connected to the preparation pool 13 through the separation gas pipeline 124. The water body 123 is collected in the gas-water separation tank 122. The air of the soil body 5 in the preparation pool 13 is sucked by the vacuum pump 111 and firstly input into the gas-water separation tank 122 through the separation gas pipeline 124. The moisture in the air gathers at the lower part of the air-water separation tank 122 and accumulates into a water body 123. The air separated from the moisture is discharged by the vacuum pump 111 through the suction air pipe 112. Separation valves 121 are respectively provided on the upper and bottom parts of the side of the air-water separation tank 122. The separation valve 121 is also connected in series on the separation air pipe 124. A vacuum gauge 125 is provided on the top of the air-water separation tank 122. The air-water separation device 12 is used to separate the air-water mixture extracted by the vacuum pump 111 to avoid damaging the vacuum pump 111.

[0029] Preparation pool 13 Figure 5As shown, the preparation pool 13 includes a side wall 131, a foundation 132, gravel 133, a non-woven fabric 134, a filter 135, a sealing film 136, a joint 137, a film discharge device 138 and a drainage board 139. The foundation 132 is built on the ground, and the side walls 131 are built around the foundation 132. The foundation 132 and the side walls 131 are both masonry structures or concrete structures. The inner and outer surfaces of the foundation 132 and the side walls 131 are coated with a waterproof layer. The top surface of the foundation 132 and the lower part of the inner side of the side wall 131 are paved with gravel 133 as For drainage and exhaust passage, non-woven fabric 134 and filter screen 135 are laid on the top surface of gravel 133 from bottom to top as anti-filtration layer, soil 5 used for experiment is piled on filter screen 135, filter screen 135, non-woven fabric 134, drainage board 139 and sealing film 136 are laid on the top surface of soil 5 from bottom to top, thereby forming a closed space around soil 5, drainage board 139 is connected to film outlet device 138 through joint 137, film outlet device 138 is connected to separation gas pipeline 124, and the length of inner cavity of preparation pool 13 is not less than 40m.

[0030] The supply device 14 is as follows Figure 6 As shown: the supply device 14 includes a water pipe 141, a supply valve 142 and a water tank 143. The water tank 143 contains air-free water 144. The water tank 143 is connected to the preparation pool 13 through the water pipe 141 at the bottom to input the air-free water 144 into the preparation pool 13. The supply valve 142 is connected in series on the water pipe 141 to control the start and stop of the delivery of the air-free water 144 and the water volume.

[0031] The vibrating and compacting device 15 is used to further compact the soil 5 after the soil 5 is sucked and compacted by the vacuum pump 111 , so that the voids inside the soil 5 are reduced, thereby increasing the density of the soil 5 .

[0032] The leveling device 16 is fixed on the truss of the trolley 27 , and when the trolley 27 moves, it drives the leveling device 16 to level the surface of the soil body 16 .

[0033] Cutting subsystem 2 Figure 7 As shown: the cutting subsystem 2 includes a cutter tooth 21, a tooth seat 22, a force sensor 23, a cutting connection device 24, an angle adjustment hydraulic cylinder 25, a height adjustment hydraulic cylinder 26, a trolley 27, a track 28 and a traction system 29. The cutting subsystem 2 is used for dynamically cutting soil. The traction system 29 is arranged on both sides of the top of the preparation pool 13, the track 28 is fixed above the preparation pool 13, the trolley 27 is movably arranged on the track 28 through the wheels at the bottom, the traction system 29 fastens the two ends of the trolley 28, the top of the cutting connection device 24 and the height adjustment hydraulic cylinder 26 are fixed to the bottom of the trolley 27 in sequence, the moving end of the piston rod of the height adjustment hydraulic cylinder 26 is connected to the middle of the cutting connection device 24, the cylinder body of the angle adjustment hydraulic cylinder 25 is fixed to the front of the cutting connection device 24, the moving end of the piston rod of the angle adjustment hydraulic cylinder 25 is connected to the front of the cutting connection device 24, the tooth seat 22 is fixed to the top of the cutting connection device 24, the cutter teeth 21 and the force sensor 23 are both fixed on the tooth seat 22, and the trolley 27 moves along the track 28 under the traction of the traction system 29, thereby driving the cutter teeth 21 to linearly cut the soil 5; The cutter teeth 21 are fixed on the tooth seat 22, and the force sensor 23 is fixed on the tooth seat 22 through a flange joint. When the cutter teeth 21 cut the soil 5, the force sensor 23 synchronously measures the cutting resistance; Cutting connecting device 24 as Figure 8 As shown: the cutting connection device 24 comprises a cutting connection device 24, a cutting connection plate 241, a cutting connection frame 242 and a cutting connection arm 243, one end of the cutting connection plate 241 is connected to the force sensor 23 through a bolt-nut assembly, the other end of the cutting connection plate 241 is connected to one end of the cutting connection frame 242 through a bolt-nut assembly, the other end of the cutting connection frame 242 is rotatably arranged on one end of the cutting connection arm 243 through a hinge, and the other end of the cutting connection arm 243 is rotatably arranged on the trolley 27 through a hinge; The cylinder body of the angle adjustment hydraulic cylinder 25 is fixed on the cutting connection arm 243, and the movable end of the piston rod of the angle adjustment hydraulic cylinder 25 is rotatably connected to the cutting connection frame 242 through a hinge. The cutting connection frame 242 is driven to rotate by the extension and contraction of the piston rod of the angle adjustment hydraulic cylinder 25, thereby adjusting the cutting angle of the cutter tooth 21; The cylinder body of the height adjustment hydraulic cylinder 26 is fixed at the bottom of the trolley 27. The movable end of the piston rod of the height adjustment hydraulic cylinder 26 is rotatably connected to the cutting connecting arm 243 through a hinge. The piston rod of the height adjustment hydraulic cylinder 26 is extended and retracted to drive the cutter teeth 21 to move up and down to adjust the height of the cutter teeth 21, thereby adjusting the thickness of the soil body 5 cut by the cutter teeth 21. Traction system 29 Fig. 9As shown: the traction system 29 includes a wire rope 291, a power system 292, a traction controller 293 and a frame 294. The frame 294 is fixed on one side of the preparation pool 13. The power system 292 and the traction controller 293 are both arranged on the frame 294. The traction controller 293 is connected to the power system 292, the angle adjustment hydraulic cylinder 25 and the height adjustment hydraulic cylinder 26 through signal lines respectively. The traction controller 293 is also connected to the control device 43 through a signal line. The wire rope 291 is led out from the power system and tied to both sides of the trolley 27. The power system 292 uses a winch or an electric hoist. The traction controller 293 uses a programmable controller, a single-chip microcomputer or a microcomputer. The traction controller 293 adjusts the direction and speed of the traction trolley 27 by controlling the power system 292 under the command of the control device 43.

[0034] Measurement subsystem 3 Fig.10 As shown in the figure, the measuring subsystem 3 includes a permeable stone 31, a water pressure sensor 33, a silica gel 34 and a communication cable 35. The measuring subsystem 3 is used to measure the pore water pressure at various locations of the interface between the cutter teeth 21 and the soil 5 in real time during the cutting process of the soil 5. The water pressure sensor 33 is arranged in the hole drilled by the blade teeth 21 in the soil body 5 and fixed with silica gel 34. A communication cable 35 is arranged at one end of the water pressure sensor 33 and the communication cable 35 passes through the hole. A permeable stone 31 is arranged at the other end of the water pressure sensor 33. The upper surface of the permeable stone 31 is flush with the blade teeth 21. Between the lower surface of the permeable stone 31 and the water pressure sensor 33 is a water body 32 under pressure in the soil body 5. The water pressure sensor 33 uses a micro pressure sensor with a diameter of no more than 5 mm and a thickness of no more than 1 mm. Control subsystem 4 Fig.11 As shown: the control subsystem 4 includes a data acquisition device 41, a data line 42 and a control device 43. The control subsystem 4 is used to automatically collect and store the pore water pressure data generated during the process of the cutter teeth 21 cutting the soil 5. The communication cable 35 at one end of the water pressure sensor 33 is connected to the data acquisition device 41, and the force sensor 23 is also connected to the data acquisition device 41 through the communication cable 35. The data acquisition device 41 is connected to the control device 43 through the data line 42. The control device 43 is also connected to the cutting subsystem 2 through the data line 42. The control device 43 is provided with a parameter setting module, a cutting control module, a collection control module and a data processing module; The control device 43 is a microcomputer; The control device 43 controls the power system 292, the angle adjustment hydraulic cylinder 25 and the height adjustment hydraulic cylinder 26 through the traction controller 293 according to the set parameters, thereby controlling the cutter teeth 21 to reciprocate according to the set parameters to cut the soil 5. The data acquisition instrument 41 collects the cutting resistance value measured by the force sensor 23 and the pore water pressure value measured by the water pressure sensor 33 in real time according to the set parameters and transmits them to the controller 43. The controller 43 stores the received cutting resistance value and the pore water pressure value. The controller 43 can also transmit the cutting resistance value and the pore water pressure value to other electronic devices through the network. After the cutting meets the set requirements, the control device 43 controls the power system 292, the angle adjustment hydraulic cylinder 25 and the height adjustment hydraulic cylinder 26 to stop running and return to the initial position through the traction controller 293. The control device 43 then processes the received cutting resistance value and the pore water pressure value.

[0035] The control device 43 is connected to the force sensor 23, the water pressure sensor 33, the power system 292, the angle adjustment hydraulic cylinder 25 and the height adjustment hydraulic cylinder 26 through the data acquisition device 41 and the traction controller 293. Fig.12 shown.

[0036] When this embodiment is used, it is implemented according to the following steps: S1. Soil preparation: The soil 5 is placed in the preparation pool 13, and the air in the soil 5 in the preparation pool 13 is sucked by the vacuum pump 111, and firstly input into the air-water separation tank 122 through the separation air pipe 124, and the moisture in the air is collected at the lower part of the air-water separation tank 122 to accumulate into the water body 123, and the air separated from the moisture is discharged by the vacuum pump 111 through the suction air pipe 112, and the water tank 143 is connected to the preparation pool 13 through the water pipe 141 at the bottom to input the air-free water 144 into the preparation pool 13; The soil 5 put into the preparation pool 13 is dug from the excavation construction site, and impurities (such as stones, garbage, branches, etc.) are removed to ensure the uniformity of the soil 5. The various indicators of the soil 5 put into the preparation pool 13 should be basically consistent with the soil at the excavation construction site; S2. Setting: In the maintenance mode of the trolley 27, the control device 43 controls the power system 292 through the traction controller 293 to perform zero correction on the trolley 27 and the wire rope 291 respectively. The control device 43 sets the cutting speed of the cutter teeth 22, the acquisition frequency of the force sensor 23 and the acquisition frequency of the water pressure sensor 33 in the parameter setting module, powers on the inverter of the power system 292 to put the inverter in a ready state, and ensures that the braking and tensioning hydraulics of the traction system 29 work normally; S3. Cutting: The cutting control module of the control device 43 controls the power system 292, the angle adjustment hydraulic cylinder 25 and the height adjustment hydraulic cylinder 26 respectively through the traction controller 293, and drives the cutting connection frame 242 to rotate by the extension and retraction of the piston rod of the angle adjustment hydraulic cylinder 25, thereby adjusting the cutting angle of the cutter teeth 21, and drives the cutter teeth 21 to move up and down by the extension and retraction of the piston rod of the height adjustment hydraulic cylinder 26 to adjust the height of the cutter teeth 21, thereby adjusting the thickness of the soil body 5 cut by the cutter teeth 21, and the trolley 27 moves along the track 28 under the traction of the traction system 29, thereby driving the cutter teeth 21 to linearly cut the soil body 5 at the set cutting speed; The moving speed of the cutter teeth 21 when cutting the soil 5 is not more than 3m / s and the fluctuation range of the moving speed is not more than 5%. When cutting, the first 5m is an acceleration section where the speed increases from zero to the moving speed, and the last 5m is a deceleration section where the speed drops from the moving speed to zero. The section between the acceleration section and the deceleration section is a cutting section of the moving speed, and the length of the cutting section is not less than 30m. S4 measurement: the blade 21 cutting soil 5 force sensor 23 synchronously measures the cutting resistance according to the set acquisition frequency, the water pressure sensor 33 synchronously measures the pore water pressure at each interface of the blade 21 and the soil 5 during the cutting process according to the set acquisition frequency; S5. Collection: The collection control module of the control device 43 receives and stores the cutting resistance value measured by the force sensor 23 and the pore water pressure value measured by the water pressure sensor 33 through the data acquisition device 41 at a frequency of 1mm per operation of the cutter teeth 21; S6. Analysis: The data processing module of the control device 43 determines the range of the dilatancy zone according to the received cutting resistance value and pore water pressure value, and the specific steps are as follows: First, using drawing software, the positions where the measured pore water pressure is positive are marked with "+" and the negative values ​​are marked with "-". Next, for the areas adjacent to the positive and negative values, difference processing is performed to obtain the positions where the pore water pressure is 0. The positions where the pore water pressure is 0 are then plotted as data points on the plane diagram of the tooth surface 211 of the cutter tooth 21. Finally, the points where the pore water pressure is 0 are connected into a line, which is the boundary line between the dilatancy zone and the non-dilatancy zone. The area where the pore water pressure value is negative is the final determined dilatancy zone range. S7. Reset: Stop the trolley 27 to stop the cutting of the soil 5 by the cutter teeth 21, and then retreat the trolley 27 to the initial zero position at a set speed.

[0037] In the above steps, S2 to S7 are as follows: Fig.13 shown.

[0038] The specific method and process of the above difference processing are as follows: Using this embodiment, for fine sand with a standard penetration hammer number N of 32, under the conditions of cutting angle α=45°, cutting speed v=0.5m / s, and cutting thickness h=0.1m, the pore pressure values ​​collected on the surface of the cutter teeth 21 are shown in Table 1, and the range of the shear expansion zone is determined as follows Fig.14 As shown, Fig.14 The SD in the middle is the shear expansion zone.

[0039] Table 1 shows that the measured pore water pressure values ​​are basically symmetrical along the central axis of the cutter tooth 21, and the pore pressure value gradually changes from negative to positive from the tooth tip of the cutter tooth 21 to the tooth seat 22. It can be known from the relevant theories of soil mechanics that saturated dense fine-grained soil will undergo shear expansion when subjected to shear (cutting), which is macroscopically manifested as a negative pore water pressure value. According to the effective stress principle, the generation of negative pore pressure will increase the effective stress, making the soil more difficult to shear (cut) and dig. Compared with other positions, the negative pore water pressure values ​​at the central axis and tooth tip are the largest, indicating that the shear expansion of the soil here is the strongest.

[0040] Fig.14 It shows that the shear expansion zone does not exist on the tooth surface 211 of the entire tooth 21, but is mainly distributed in the lower half of the tooth 21 and near the center axis of the tooth 21. The shear expansion zone is in a pointed cone shape and is basically symmetrical left and right along the center axis of the tooth 21.

[0041] Table 1:

Claims

1. An experimental system for determining the range of the shear expansion zone of dense fine-grained soil, characterized by: The invention comprises a preparation subsystem (1), a cutting subsystem (2), a measuring subsystem (3) and a control subsystem (4) which are arranged on the ground. The cutting subsystem (2) is arranged on the preparation subsystem (1), the measuring subsystem (3) is arranged on the cutting subsystem (2), and the control subsystem (4) is connected to the measuring subsystem (3). The preparation subsystem (1) comprises a suction device (11), a gas-water separation device (12), a preparation pool (13), a supply device (14), a vibration compaction device (15) and a leveling device (16). A preparation pool (13) is arranged on the ground, a soil body (5) is arranged in the preparation pool (13), a suction device (11) and an air-water separation device (12) are arranged on one side of the preparation pool (13), a supply device (14) is arranged on the other side of the preparation pool (13), a vibrating and compacting device (15) and a leveling device (16) are arranged above the soil body (5) in the preparation pool (13), the suction device (11) sucks air from the soil body (5) in the preparation pool (13) through the air-water separation device (12), the air-water separation device (12) separates the water contained in the air sucked out by the suction device (11), the supply device (14) outputs air-free water (144) to the preparation pool (13), the vibrating and compacting device (15) vibrates and compacts the soil body (5) in the preparation pool (13), and the leveling device (16) smoothes the surface of the soil body (5) in the preparation pool (13); The cutting subsystem (2) includes a cutting tooth (21), a tooth seat (22), a force sensor (23), a cutting connection device (24), an angle adjustment hydraulic cylinder (25), a height adjustment hydraulic cylinder (26), a trolley (27), a track (28) and a traction system (29). The traction system (29) is arranged on both sides of the top of the preparation pool (13), the track (28) is fixed above the preparation pool (13), the trolley (27) is movably arranged on the track (28) through the wheels at the bottom, the traction system (29) fastens the two ends of the trolley (28), the top of the cutting connection device (24) and the height adjustment hydraulic cylinder (26) are fixed to the bottom of the trolley (27) in sequence, the movable end of the piston rod of the height adjustment hydraulic cylinder (26) is connected to the middle of the cutting connection device (24), the cylinder body of the angle adjustment hydraulic cylinder (25) is fixed to the front of the cutting connection device (24), the tooth seat (22) is fixed to the top of the cutting connection device (24), and the cutter teeth (21) and the force sensor (23) are both fixed on the tooth seat (22); The measuring subsystem (3) includes a permeable stone (31), a water pressure sensor (33), silica gel (34) and a communication cable (35). A water pressure sensor (33) is arranged in a hole drilled by the blade teeth (21) in the soil body (5) and fixed with silica gel (34); a communication cable (35) is arranged at one end of the water pressure sensor (33) and the communication cable (35) passes through the hole; a permeable stone (31) is arranged at the other end of the water pressure sensor (33); the upper surface of the permeable stone (31) is flush with the blade teeth (21); and a water body (32) under pressure in the soil body (5) is located between the lower surface of the permeable stone (31) and the water pressure sensor (33); The control subsystem (4) includes a data acquisition device (41), a data line (42) and a control device (43). A communication cable (35) at one end of the water pressure sensor (33) is connected to a data acquisition device (41), and the force sensor (23) is also connected to the data acquisition device (41) via the communication cable (35). The data acquisition device (41) is connected to a control device (43) via a data line (42), and the control device (43) is also connected to a cutting subsystem (2) via a data line (42). The control device (43) is provided with a parameter setting module, a cutting control module, a collection control module and a data processing module.

2. The experimental system for determining the shear expansion zone of dense fine-grained soil according to claim 1, characterized in that: In the preparation subsystem (1): The suction device (11) comprises a vacuum pump (111), a suction air pipe (112) and a suction valve (113); the air inlet end of the vacuum pump (111) is connected to the air-water separation device (12) via the suction air pipe (112); and the suction valve (113) is connected in series to the suction air pipe (112); The gas-water separation device (12) comprises a separation valve (121), a gas-water separation tank (122), a separation gas transmission pipe (124) and a vacuum gauge (125); the gas outlet end of the gas-water separation tank (122) is connected to the suction gas transmission pipe (112); the gas inlet end of the gas-water separation tank (122) is connected to the preparation pool (13) via the separation gas transmission pipe (124); a water body (123) is collected in the gas-water separation tank (122); the upper part and the bottom part of the side of the gas-water separation tank (122) are respectively provided with separation valves (121); the separation gas transmission pipe (124) is also connected in series with the separation valve (121); and the top of the gas-water separation tank (122) is provided with a vacuum gauge (125); The preparation pool (13) includes a side wall (131), a foundation (132), gravel (133), a non-woven fabric (134), a filter (135), a sealing film (136), a joint (137), a film discharge device (138) and a drainage board (139). The foundation (132) is built on the ground, and the side walls (131) are built around the foundation (132). Both the foundation (132) and the side walls (131) are turned masonry structures or concrete structures. The inner and outer surfaces of the foundation (132) and the side walls (131) are coated with a waterproof layer. The top surface of the foundation (132) and the inner surface of the side walls (131) are The lower part is paved with gravel (133), the top surface of the gravel (133) is paved with non-woven fabric (134) and filter screen (135) as a filter layer from bottom to top, the soil (5) used in the experiment is piled on the filter screen (135), the top surface of the soil (5) is paved with filter screen (135), non-woven fabric (134), drainage board (139) and sealing film (136) from bottom to top, the drainage board (139) is connected to the film outlet device (138) through the joint (137), the film outlet device (138) is connected to the separation gas transmission pipe (124), and the length of the inner cavity of the preparation pool (13) is not less than 40m; The supply device (14) comprises a water delivery pipe (141), a supply valve (142) and a water tank (143). The water tank (143) contains still water (144). The water tank (143) is connected to the preparation pool (13) via the water delivery pipe (141) at the bottom. The supply valve (142) is connected in series to the water delivery pipe (141). The vibrating and compacting device (15) is used to further compact the soil (5) after the soil (5) is sucked and compacted by the vacuum pump (111), so that the voids inside the soil (5) are reduced, thereby increasing the density of the soil (5); The leveling device (16) is fixed on the truss of the trolley (27). When the trolley (27) moves, it drives the leveling device (16) to level the surface of the soil body (16).

3. The experimental system for determining the range of the shear expansion zone of dense fine-grained soil as claimed in claim 2, characterized in that: In the cutting subsystem (2): The blade teeth (21) are fixed on the tooth seat (22), and the force sensor (23) is fixed on the tooth seat (22) through a flange joint; The cutting connection device (24) comprises a cutting connection device (24), a cutting connection plate (241), a cutting connection frame (242) and a cutting connection arm (243); one end of the cutting connection plate (241) is connected to the force sensor (23) via a bolt-nut assembly; the other end of the cutting connection plate (241) is connected to one end of the cutting connection frame (242) via a bolt-nut assembly; the other end of the cutting connection frame (242) is rotatably arranged on one end of the cutting connection arm (243) via a hinge; the other end of the cutting connection arm (243) is rotatably arranged on the trolley (27) via a hinge; The cylinder body of the angle adjustment hydraulic cylinder (25) is fixed on the cutting connection arm (243), and the movable end of the piston rod of the angle adjustment hydraulic cylinder (25) is rotatably connected to the cutting connection frame (242) through a hinge; The cylinder body of the height adjustment hydraulic cylinder (26) is fixed to the bottom of the trolley (27), and the movable end of the piston rod of the height adjustment hydraulic cylinder (26) is rotatably connected to the cutting connecting arm (243) through a hinge; The traction system (29) comprises a steel wire rope (291), a power system (292), a traction controller (293) and a frame (294). The frame (294) is fixed on one side of the preparation pool (13). The power system (292) and the traction controller (293) are both arranged on the frame (294). The traction controller (293) is respectively connected to the power system (292), the angle adjustment hydraulic cylinder (25) and the height adjustment hydraulic cylinder (26) through signal lines. The traction controller (293) is also connected to the control device (43) through signal lines. The steel wire rope (291) is led out from the power system and then tied to both sides of the trolley (27).

4. The experimental system for determining the range of the shear expansion zone of dense fine-grained soil as claimed in claim 3, characterized in that: The power system (292) is selected from a winch or an electric hoist, and the traction controller (293) is selected from a programmable controller, a single chip microcomputer or a microcomputer; The water pressure sensor (33) is a micro pressure sensor; The control device (43) is selected from a microcomputer; The control device (43) controls the power system (292), the angle adjustment hydraulic cylinder (25) and the height adjustment hydraulic cylinder (26) through the traction controller (293) according to the set parameters, thereby controlling the cutter teeth (21) to reciprocate according to the set parameters to cut the soil (5). The data acquisition instrument (41) collects the cutting resistance value measured by the force sensor (23) and the pore water pressure value measured by the water pressure sensor (33) in real time according to the set parameters and transmits them to the controller (43). The controller (43) stores the received cutting resistance value and the received pore water pressure value. After the cutting reaches the set requirements, the control device (43) controls the power system (292), the angle adjustment hydraulic cylinder (25) and the height adjustment hydraulic cylinder (26) through the traction controller (293) to stop running and return to the initial position. The control device (43) then processes the received cutting resistance value and the received pore water pressure value.

5. The method for using the experimental system for determining the range of the shear expansion zone of dense fine-grained soil according to claim 4, characterized in that: Follow these steps to implement: S1. Soil preparation: A soil body (5) is placed in a preparation pool (13). The air in the soil body (5) in the preparation pool (13) is sucked by a vacuum pump (111) and firstly input into an air-water separation tank (122) through a separation air delivery pipe (124). The moisture in the air is collected at the lower part of the air-water separation tank (122) and accumulated into a water body (123). The air separated from the moisture is discharged by the vacuum pump (111) through the suction air delivery pipe (112). The water tank (143) is connected to the preparation pool (13) through a water delivery pipe (141) at the bottom to input airless water (144) into the preparation pool (13); S2. Setting: In the maintenance mode, the control device (43) controls the power system (292) through the traction controller (293) to perform zero-position correction on the trolley (27) and the wire rope (291), respectively. The control device (43) sets the cutting speed of the cutter teeth (22), the acquisition frequency of the force sensor (23), and the acquisition frequency of the water pressure sensor (33) through the parameter setting module, and powers on the inverter of the power system (292) to put the inverter in a ready state, while ensuring that the braking and tensioning hydraulics of the traction system (29) work normally. S3. Cutting: The cutting control module of the control device (43) controls the power system (292), the angle adjustment hydraulic cylinder (25) and the height adjustment hydraulic cylinder (26) respectively through the traction controller (293), and drives the cutting connecting frame (242) to rotate by the extension and retraction of the piston rod of the angle adjustment hydraulic cylinder (25), thereby adjusting the cutting angle of the cutter teeth (21), and drives the cutter teeth (21) to move up and down by the extension and retraction of the piston rod of the height adjustment hydraulic cylinder (26) to adjust the height of the cutter teeth (21), thereby adjusting the thickness of the soil body (5) cut by the cutter teeth (21), and the trolley (27) moves along the track (28) under the traction of the traction system (29), thereby driving the cutter teeth (21) to linearly cut the soil body (5) at a set cutting speed; S4. Measurement: When the blade (21) cuts the soil (5), the force sensor (23) synchronously measures the cutting resistance at a set acquisition frequency, and the water pressure sensor (33) synchronously measures the pore water pressure at various locations of the interface between the blade (21) and the soil (5) during the cutting process of the soil (5); S5. Collection: The collection control module of the control device (43) receives and stores the cutting resistance value measured by the force sensor (23) and the pore water pressure value measured by the water pressure sensor (33) through the data acquisition device (41); S6. Analysis: The data processing module of the control device (43) determines the range of the dilatancy zone according to the received cutting resistance value and pore water pressure value, and the specific steps are as follows: First, the positions where the measured pore water pressure is positive are marked with "+" and the negative values ​​are marked with "-". Then, for the areas adjacent to the positive and negative values, difference processing is performed to obtain the position where the pore water pressure is zero. Then, the position where the pore water pressure is zero is plotted as a data point on the plane diagram of the tooth surface (211) of the cutter tooth (21); Finally, connect the points where the pore water pressure is zero into a line, which is the boundary between the dilatancy zone and the non-dilatancy zone. The area with negative pore water pressure is the final dilatancy zone range. S7. Reset: The control device (43) controls the power system (292) through the traction controller (293) to stop the trolley (27) from running so as to stop the cutting of the soil (5) by the blade (21), and retracts the piston rods of both the angle adjustment hydraulic cylinder (25) and the height adjustment hydraulic cylinder (26). Then, the control device (43) controls the power system (292) through the traction controller (293) to make the trolley (27) retreat to the initial zero position at a set speed.

6. The method for using the experimental system for determining the range of the shear expansion zone of dense fine-grained soil as claimed in claim 5, characterized in that: In step S1, the soil (5) placed in the preparation pool (13) is dug from the excavation construction site, and impurities therein are removed to ensure the uniformity of the soil (5); In step S3, the moving speed of the cutter teeth (21) when cutting the soil (5) is not greater than 3 m / s and the fluctuation range of the moving speed is not greater than 5%. During cutting, the first 5 m is an acceleration section where the speed increases from zero to the moving speed, and the last 5 m is a deceleration section where the speed decreases from the moving speed to zero. The section between the acceleration section and the deceleration section is a cutting section of the moving speed, and the length of the cutting section is not less than 30 m. In step S5, the collection control module of the control device (43) receives and stores the cutting resistance value measured by the force sensor (23) and the pore water pressure value measured by the water pressure sensor (33) at a frequency of once every 1 mm of movement of the cutter tooth (21).

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