Combined geophysical probe for soil layer and use method thereof

Abstract

The present invention relates to a combined geophysical probe for soil layers and a method of use, comprising: a combined probe, comprising a spiral plate probe and a cross plate probe, the cross plate probe being coaxially movably installed inside the spiral plate probe; a hydraulic jack, installed at the top end of the combined probe, suitable for driving the spiral plate probe and the cross plate probe to move simultaneously, or driving the cross plate probe to move alone; a reaction force system, fixed above the ground, suitable for fixing the combined probe and the hydraulic jack during the test; a measuring system, fixed above the ground, suitable for measuring the test data of the combined probe; a shear meter, installed at the top end of the cross plate probe, suitable for driving the cross plate probe to rotate. This combined geophysical probe breaks the traditional model of separating two test equipment, saving the space occupied by the equipment; during on-site operations, there is no need for complex site planning for the placement of multiple equipment, which is convenient and fast, and improves the flexibility of the overall operation.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering survey, relates to geotechnical engineering in-situ testing, and in particular to a combined geophysical probe for soil layers and a method of using the probe. Background Art

[0002] In geotechnical engineering investigations, the spiral plate load test (SPLT) and the cross-plate shear test (VST) are two commonly used in-situ testing methods: the spiral plate load test involves drilling a spiral bearing plate to a predetermined depth underground, applying pressure through a force transfer rod and measuring the amount of settlement. This can be used to determine data such as the compression modulus, consolidation coefficient, and bearing capacity of the foundation soil; the cross-plate shear test involves inserting a cross-plate probe into the soil and twisting it to measure the resistance torque when the soil fails, thereby determining the undrained shear strength and residual shear strength of the soil.

[0003] The traditional spiral plate load test and cross plate shear test have the following problems:

[0004] 1. The two tests require different equipment to operate, which not only results in more equipment costs when conducting the two tests, but also makes the test process cumbersome, greatly increases the time cost required for the test, and reduces the efficiency of the survey work;

[0005] 2. Before the cross-plate shear test is carried out, it is necessary to pre-drill holes with the help of a drilling rig or other hole-making machinery. The operation process is complicated, and the site conditions and equipment requirements are high, and there are great restrictions.

[0006] To this end, we propose a combined geophysical probe for soil layers and a method of use to solve the above problems. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a combined geophysical exploration test method with high survey quality and minimal soil disturbance.

[0008] In order to solve the above problems, the technical solution of the present invention is:

[0009] A combined geophysical probe for soil layers, comprising:

[0010] The combined probe includes a spiral plate probe and a cross plate probe, wherein the cross plate probe is coaxially movable and installed inside the spiral plate probe;

[0011] The hydraulic jack is installed at the top of the combined probe and is suitable for driving the spiral plate probe and the cross plate probe to move simultaneously, or driving the cross plate probe to move alone;

[0012] The reaction force system is fixed above the ground and is suitable for fixing the joint probe and hydraulic jack during the test;

[0013] The measuring system is fixed above the ground and is suitable for measuring the test data of the combined probe;

[0014] The shear meter is mounted on the top end of the cross-plate probe and is suitable for driving the cross-plate probe to rotate.

[0015] In a further embodiment, a conversion spacer is installed between the hydraulic jack and the combined probe;

[0016] When installing the conversion pad and disassembling the shear gauge: the spiral plate probe and the cross plate probe move downward at the same time;

[0017] When the conversion block is removed: the cross plate probe moves downward and the spiral plate probe remains stationary.

[0018] In a further embodiment, the bottom end portion of the spiral plate probe is circumferentially hinged with a probe nozzle;

[0019] When the probe nozzle is opened: the cross plate probe is pushed out by the hydraulic jack;

[0020] When the probe nozzle is closed: the cross-plate probe is located inside the spiral plate probe.

[0021] In a further embodiment, the spiral plate probe includes a spiral plate force transmission rod and a spiral load plate. The top end surface of the spiral plate force transmission rod is tightly fitted with the bottom end surface of the conversion pad. The spiral load plate is spirally fixed on the circumference of the bottom end of the spiral plate force transmission rod, and the probe nozzle is located below the spiral load plate.

[0022] In a further embodiment, the spiral plate force transmission rod is hollow.

[0023] In a further embodiment, a force sensor is fixedly mounted on the spiral plate force transmission rod.

[0024] In a further embodiment, the cross-plate probe includes a cross-plate force transmission rod, a cross-plate shaft and a cross-plate. The top end of the cross-plate force transmission rod is fixedly mounted on the hydraulic jack, the outer side of the top end of the cross-plate force transmission rod is suitable for mounting a conversion pad, the bottom end of the cross-plate force transmission rod is mounted with the top end of the cross-plate shaft, and the bottom end of the cross-plate shaft is fixedly mounted with the cross-plate.

[0025] In a further embodiment, the outer side of the bottom end of the cross plate is configured to be an acute angle.

[0026] In a further embodiment, the cross section of the conversion pad is a C-shaped structure suitable for installation and removal.

[0027] A method for using a combined geophysical probe for soil layers, the method comprising the following steps:

[0028] Step S101: Drilling a hole with a spiral plate probe:

[0029] Fix the combined probe on the ground of the soil to be tested, and use the spiral plate probe to drill into the soil until the predetermined test position;

[0030] Step S103: spiral plate load test:

[0031] Use the spiral plate probe to carry out the spiral plate load test on the surrounding soil;

[0032] Step S105: Cross-plate shear test:

[0033] Remove the conversion pad, push out the cross plate probe, and then install the shear meter

[0034] A cross-plate shear test is performed on the soil below the spiral plate probe.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The spiral plate force transmission rod of this combined geophysical probe adopts a hollow rod structure, in which the cross-plate probe and the cross-plate force transmission rod are cleverly set. This design breaks the traditional mode of separating the two test equipment, greatly saving the space occupied by the equipment; and during the transportation process, it reduces the space and labor costs required for transporting multiple equipment separately. During on-site operations, there is no need for complex site planning for the placement of multiple equipment. It is convenient and fast, and improves the flexibility of the overall operation.

[0037] 2. This combined geophysical probe uses a spiral plate probe as a drilling rig to complete the drilling operation during the process of screwing into the soil. Subsequently, the spiral plate load test and cross-plate shear test are carried out directly in the original soil. The drilling can meet the requirements of both tests at the same time, eliminating the tedious steps of pre-drilling required in traditional cross-plate shear tests, reducing the investment and operation time of drilling equipment, significantly shortening the entire test cycle, and improving the work efficiency of geotechnical engineering surveys.

[0038] 3. The bottom end of the spiral plate force transmission rod of this combined geophysical probe is hinged with a probe nozzle, which can be opened and closed. When conducting a spiral load test, the probe nozzle is closed. When switching to the cross-plate shear test, the cross-plate pushes the probe nozzle downward and pushes it into the soil below the spiral load plate, avoiding interference of the soil after the spiral load test on the cross-plate shear test process, ensuring that the cross-plate is tested in a purely original soil shear environment, ensuring the reliability of the two test results; and the entire test process is carried out in the original soil, without disturbing the soil or taking samples for testing, which truly reflects the mechanical properties of the soil in its natural state.

[0039] 4. This combined geophysical probe sets a conversion pad between the hydraulic jack and the spiral plate probe and the cross plate probe. During the jacking drilling and spiral plate load tests, the conversion pad is installed so that the hydraulic jack can jointly support the cross plate dowel rod and the conversion pad, and then simultaneously jack the spiral plate dowel rod and the cross plate dowel rod; during the cross plate shear test, the conversion pad is removed so that the hydraulic jack only supports the cross plate dowel rod, which is suitable for pushing the cross plate downward out of the probe nozzle; the switching is flexible and convenient, and the original structure is utilized, with low cost.

[0040] 5. The combined geophysical probe integrates the spiral plate probe and the cross-plate probe into an integrated structure, which reduces the purchase and maintenance costs of various equipment. At the same time, the efficient test process shortens the operation time and reduces labor and time costs. In addition, the test can be carried out in the original soil, avoiding the costs incurred by additional operations such as sampling and transporting samples. This reduces the overall cost of in-situ testing in geotechnical engineering investigations and provides a more cost-effective solution for engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A flow chart of a method for using a combined geophysical probe for soil layers;

[0042] Figure 2 is a schematic diagram of a combined geophysical probe for soil layers;

[0043] Figure 3 A schematic diagram of a conversion pad for a combined geophysical probe for soil layers;

[0044] Figure 4 This is one of the schematic diagrams of a combined geophysical probe for soil layers;

[0045] Figure 5 This is the second schematic diagram of a combined geophysical probe for soil layers.

[0046] In the figure: 1. Reaction system; 11. Reaction system anchor; 2. Measuring system; 21. Measuring system anchor; 3. Hydraulic jack; 31. Conversion pad; 4. Shear gauge; 41. Rotating handle; 42. Dial indicator; 5. Screw plate probe; 51. Screw plate force transfer rod; 52. Screw load plate; 53. Probe nozzle; 54. Force sensor; 6. Cross plate probe; 61. Cross plate force transfer rod; 62. Cross plate shaft; 63. Cross plate. DETAILED DESCRIPTION

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0048] Example 1:

[0049] A combined geophysical probe for soil layers, such as Figures 2 to 5 As shown, the combined geophysical probe is fixedly installed on the ground above the soil to be tested, with the bottom end penetrating into the soil. The above-ground part includes a reaction system 1, a measuring system 2, a hydraulic jack 3, a shear meter 4 and the upper end of the combined probe. The two ends of the reaction system 1 are respectively fixedly installed with the top ends of the reaction system anchors 11. The bottom ends of the two reaction system anchors 11 are fixedly installed in the soil, which is suitable for providing reaction force during the jacking process of the combined probe to ensure the smooth progress of the test; the bottom end of the reaction system 1 is fixedly installed with the top end of the hydraulic jack 3, and the hydraulic jack 3 is fixedly installed. The top end of the combined probe is mounted on the bottom end of the hydraulic jack 3, and a shear gauge 4 is removably mounted on the top end of the combined probe. The shear gauge 4 is located below the hydraulic jack 3 and is suitable for providing jacking pressure and torque to the combined probe during the test. The top end of the combined probe is also fixedly mounted with a measurement system 2, which is located below the shear gauge 4. The top ends of the measurement system ground anchors 21 are fixedly mounted on each end of the measurement system 2. The bottom ends of the two measurement system ground anchors 21 are fixedly installed in the soil, suitable for monitoring test data during the test. For detailed information on the specific structure, connection method, function, and model of the reaction system 1, measurement system 2, hydraulic jack 3, and shear gauge 4, please refer to the "Engineering Geology Handbook" (Fifth Edition) published by China Architecture & Building Press, and will not be repeated in this embodiment.

[0050] like Figure 2 、 Figure 4 、 Figure 5As shown, the combined probe includes a spiral plate probe 5 and a cross plate probe 6. The cross plate probe 6 is installed inside the spiral plate probe 5. The spiral plate probe 5 is made of stainless steel. The spiral plate probe 5 includes a spiral plate force transmission rod 51, a spiral load plate 52, a probe nozzle 53 and a force sensor 54. The spiral plate force transmission rod 51 is a hollow structure, and the cross plate probe 6 is installed inside the spiral plate force transmission rod 51. The force sensor 54 is fixedly installed at the lower end of the spiral plate force transmission rod 51. The spiral spiral load plate 52 is fixedly installed on the circumference of the bottom end of the spiral plate force transmission rod 51. The spiral load plate 52 Located below the force sensor 54, the bottom end of the spiral plate force transmission rod 51 is hinged with a probe nozzle 53. The probe nozzle 53 is located below the spiral load plate 52. The probe nozzle 53 includes two semi-conical structures, and the probe nozzle 53 can be opened or closed. During the top drilling and spiral plate load test, the probe nozzle 53 is in a closed state, forming a conical structure. During the cross-plate shear test, the probe nozzle 53 is opened, and the outer surface of the probe nozzle 53 is still tilted inward, so that after the cross-plate probe 6 is pulled back into the spiral plate probe 5, when drilling downward again, the probe nozzle 53 can gradually close under the action of the soil. Preferably, the outer diameter of the spiral plate force transmission rod 51 is 180mm, the inner diameter is 130mm, and the wall thickness is 25mm; the diameter of the spiral load plate 52 is 252mm, and the projected area is 500cm 2 The thickness of the spiral load plate 52 is 5 mm and the pitch is 80 mm; the surface of the spiral load plate 52 should be processed smoothly to reduce the disturbance to the soil.

[0051] The cross-plate probe 6 is made of stainless steel. The cross-plate probe 6 includes a cross-plate force transmission rod 61, a cross-plate shaft 62 and a cross-plate 63. The top end of the cross-plate force transmission rod 61 is installed on the bottom end of the hydraulic jack 3, and the bottom end of the cross-plate force transmission rod 61 is fixedly installed with the top end of the cross-plate shaft 62. The diameter of the cross-plate force transmission rod 61 is larger than the diameter of the cross-plate shaft 62. The bottom end of the cross-plate shaft 62 is fixedly installed with the cross-plate 63. The cross-plate 63 is vertically installed together using two plate-like structures, and the cross-section forms a cross-shaped structure. The outer sides of the bottom ends of the two plate-like structures are acute angles, which are suitable for the cross-plate 63 to push downward. During the jacking drilling and spiral plate load tests, the cross-plate 63 is located in the spiral plate force transmission rod 51. In the cross-plate shear test, the cross-plate 63 pushes downward to open the probe nozzle 53, and a cross-plate shear test is performed in the soil below the spiral load plate 52. Preferably, the surface roughness of the cross plate 63 is no more than 6.3 μm; a 75 mm × 150 mm cross plate 63 is more appropriate in shallow soft silt, silty clay and soft clay, and a 50 mm × 100 mm cross plate 63 is used in slightly harder soil; the curvature of the cross plate shaft 62 and the cross plate force transmission rod 61 within the length range of the lowest 5 m is no more than 0.05%, and the curvature of the remaining cross plate force transmission rods 61 is no more than 0.1%; the connection of the cross plate force transmission rod 61 should have good interchangeability. If the cross plate force transmission rod 61 is connected with a tapered thread, there should be no shaking after connection. If the cross plate force transmission rod 61 is connected with a cylindrical thread, the root and shoulder of the thread should be able to fit tightly after tightening. Preferably, the plate-like structure of the cross plate 63 has a height of 100 mm, a width of 50 mm, a height-to-width ratio of 2, a thickness-to-width ratio of 0.04, a radius of rotation of the cross plate 63 of 25 mm, an acute angle of the outer side of the bottom end of the cross plate 63 of 60°, a diameter of the cross plate shaft 62 of 13 mm, and a length of 50 mm.

[0052] like Figure 2 、 Figure 3As shown, the bottom end face of the hydraulic jack 3 is in close contact with the top face of the conversion pad 31, and the bottom end face of the conversion pad 31 is in close contact with the top face of the spiral plate force transmission rod 51. The conversion pad 31 is a cylindrical structure, and a long hole is formed in the middle of the conversion pad 31, and a cross plate force transmission rod 61 is passed through the long hole. The top end of the cross plate force transmission rod 61 is flush with the top end of the conversion pad 31, and the top face of the cross plate force transmission rod 61 is in close contact with the bottom end face of the hydraulic jack 3; during the jacking drilling and spiral plate load tests, the conversion pad 31 is installed and the shear instrument 4 is removed, so that the hydraulic jack 3 can jointly support the cross plate force transmission rod 61 and the conversion pad 31, and then simultaneously jack the spiral plate force transmission rod 51 and the cross plate force transmission rod 61; during the cross plate shear test, the conversion pad 31 is removed, so that the hydraulic jack 3 only supports the cross plate force transmission rod 61 and the conversion pad 31. The cross plate force transfer rod 61 is suitable for pushing the cross plate 63 downward out of the probe nozzle 53; then the shearing instrument 4 is installed at the position of the conversion pad 31, that is, the shearing instrument 4 is installed at the top end of the cross plate force transfer rod 61, the shearing instrument 4 includes a horizontally arranged rotating handle 41 and a dial indicator 42 for measuring the deformation of the steel ring, the rotating handle 41 is fixedly mounted on the cross plate force transfer rod 61, and the dial indicator 42 is fixedly mounted on one end of the rotating handle 41, which is suitable for measuring the data in the cross plate shear test; when the cross plate 63 is located in the spiral plate force transfer rod 51, that is, during the jacking drilling and spiral plate load test, the height difference between the top end of the cross plate force transfer rod 61 and the top end of the spiral plate force transfer rod 51, that is, the length of the conversion pad 31, is greater than the height difference between the spiral load plate 52 and the cross plate 63, which is suitable for the cross plate 63 to be able to push out the probe nozzle 53. Preferably, the conversion pad 31 can be made of a hard metal material with a certain deformation ability, and the cross-section of the conversion pad 31 is a C-shaped structure, so that the conversion pad 31 can be disassembled by a snap; the conversion pad 31 can also be set as two parts that are snapped together and can be detachably installed together by bolts or hinges.

[0053] Example 2:

[0054] A method for using a combined geophysical probe for soil layers, such as Figures 1 to 5 As shown, the following steps are included:

[0055] S101, spiral plate probe 5 drilling

[0056] First, use the spiral plate probe 5 to drill downward at the predetermined test position, and use the hydraulic jack 3 to push the spiral plate probe 5 downward to achieve this. When drilling, stop drilling 20cm to 30cm above the predetermined test depth, and remove the compressed or disturbed soil layer at the bottom of the hole;

[0057] The spiral plate probe 5 is slowly pushed against the top to continue drilling downward. Since the spiral load plate 52 is a spiral structure, the spiral plate probe 5 will rotate during the drilling process under the action of the surrounding soil. It operates according to the principle of drilling one pitch per rotation, which is suitable for reducing disturbance to the soil.

[0058] S103, spiral plate load test

[0059] After the spiral plate probe 5 reaches the test depth, the spiral plate load test is started. During the test, the loading classification and stability standards are adopted, and the hydraulic jack is used to add load in 3 stages. For sand, medium and low compressible clay, and silt, the load value for each stage should be 50kPa, and for highly compressible soil, 25kPa should be used.

[0060] After each level of loading, the settlement of the spiral load plate 52 is read at intervals of 5 minutes, 5 minutes, 10 minutes, 10 minutes, 15 minutes, and 15 minutes, and then readings are taken every half hour. When the settlement is less than 0.1 mm per hour for two consecutive hours, the relative stability standard is reached and the next level of load can be applied; repeat this step until the spiral plate load test is completed.

[0061] Undrained deformation modulus of soil E u It can be calculated by formula (1):

[0062] (1)

[0063] Where, E u is the undrained deformation modulus of the soil, in MPa; Δp is the pressure increment, in MPa; s is the settlement value after consolidation under the pressure increment Δp; D2 is the diameter of the spiral loading plate 52, in mm.

[0064] S105, cross plate shear test

[0065] like Figure 4 As shown, after the spiral plate load test is completed, the conversion pad 31 is removed, and the hydraulic jack 3 is continued to be controlled to push the cross plate probe 6, so that the cross plate 63 pushes open the probe nozzle 53 and pushes into the soil below the spiral plate probe 5, and then the shear instrument 4 is installed at the top end of the cross plate force transmission rod 61 to perform the cross plate shear test.

[0066] The shearing instrument 4 consists of a horizontal rotating handle 41 and a dial indicator 42 for measuring the deformation of the steel ring. After installation, it needs to be leveled and calibrated. A level ruler can be used to calibrate the position and adjust the dial indicator 42 to zero.

[0067] At the beginning of the test, the stopwatch is started and the cross plate 63 is rotated 1° to 2° every 10 seconds, that is, the cross plate shaft 62 is rotated at a rate of about one to two turns every 10 seconds. The deformation reading of the steel ring is recorded once every turn until the soil is sheared (that is, the maximum reading is read). The reading is continued for 1 minute. The force applied to the steel ring at this time is the total force when the original soil is sheared, that is, the maximum degree of the dial indicator 42 when the damage is reduced. For details about the specific structure and connection method of the steel ring, please refer to the "Engineering Geology Handbook" (Fifth Edition) published by China Architecture & Building Press, which will not be described in detail in this embodiment.

[0068] After completing the above-mentioned undisturbed soil shear test, the soil is completely destroyed and left to stand for 60 seconds. Then, the test is repeated according to the above steps at a rate of one to two turns per 10 seconds to obtain the total force of the disturbed soil, which is the maximum degree of the dial indicator 42 during friction. value;

[0069] Shear strength of soil C u It can be calculated by formula (2) and formula (3):

[0070] (2)

[0071] (3)

[0072] Where C u is the shear strength of the soil; β is the reduction coefficient, which is 0.7-0.8 for clay soil and 0.8-0.9 for sandy soil; K is the cross plate 63 constant, unit is m -2 ; C is the steel ring coefficient, unit is kN / 0.01mm; R y The maximum degree of the dial indicator 42 when the loss is reduced, the unit is 0.01mm, measured by the shear instrument 4; R g is the maximum degree of the dial indicator 42 during friction, the unit is 0.01 mm, measured by the shear meter 4; R is the radius of the cross plate 63 when rotating; D is the plate structure width of the cross plate 63; H is the plate structure height of the cross plate 63.

[0073] Continue to push downward to the next test point and repeat the above-mentioned S103 spiral plate load test and S105 cross plate shear test until the measurement of all test points in the same test hole is completed; the vertical distance between test points in the same test hole should generally be greater than or equal to 1m, and should be arranged in combination with soil layer changes and uniformity.

[0074] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A combined geophysical probe for soil layers, characterized in that: include: A combined probe comprises a spiral plate probe (5) and a cross plate probe (6), wherein the cross plate probe (6) is coaxially movably installed in the spiral plate probe (5); An oil pressure jack (3) is installed at the top end of the combined probe and is suitable for driving the spiral plate probe (5) and the cross plate probe (6) to move simultaneously, or driving the cross plate probe (6) to move alone; A reaction force system (1) fixed above the ground, suitable for fixing the combined probe and the hydraulic jack (3) during the test; A measuring system (2), fixed above the ground, adapted to measure the test data of the combined probe; A shear meter (4) is mounted on the top end of the cross-plate probe (6) and is suitable for driving the cross-plate probe (6) to rotate; A conversion pad (31) is installed between the oil pressure jack (3) and the combined probe: When the conversion pad (31) is installed and the shearing instrument (4) is disassembled: the spiral plate probe (5) and the cross plate probe (6) move downward simultaneously; When the conversion pad (31) is removed: the cross plate probe (6) moves downward, and the spiral plate probe (5) remains stationary; The bottom end of the spiral plate probe (5) is circumferentially hinged with a probe nozzle (53); When the probe nozzle (53) is opened: the cross plate probe (6) is pushed out by the hydraulic jack (3); When the probe nozzle (53) is closed, the cross plate probe (6) is located inside the spiral plate probe (5).

2. The combined geophysical probe for soil layer according to claim 1, characterized in that: The spiral plate probe (5) comprises a spiral plate force transmission rod (51) and a spiral load plate (52). The top end surface of the spiral plate force transmission rod (51) is tightly fitted with the bottom end surface of the conversion pad (31). The spiral load plate (52) is fixedly mounted on the circumference of the bottom end of the spiral plate force transmission rod (51) by a spiral, and the probe nozzle (53) is located below the spiral load plate (52).

3. The combined geophysical probe for soil layer according to claim 2, characterized in that: The spiral plate force transmission rod (51) is hollow.

4. The combined geophysical probe for soil layer according to claim 3, characterized in that: A force sensor (54) is fixedly mounted on the spiral plate force transmission rod (51).

5. The combined geophysical probe for soil layer according to claim 4, characterized in that: The cross-plate probe (6) comprises a cross-plate force transmission rod (61), a cross-plate shaft rod (62) and a cross-plate (63); the top end of the cross-plate force transmission rod (61) is fixedly mounted on the hydraulic jack (3), and the outer side of the top end of the cross-plate force transmission rod (61) is suitable for fitting the conversion pad (31); the bottom end of the cross-plate force transmission rod (61) is mounted on the top end of the cross-plate shaft rod (62), and the bottom end of the cross-plate shaft rod (62) is fixedly mounted on the cross-plate (63).

6. The combined geophysical probe for soil layers according to claim 5, characterized in that: The outer side of the bottom end of the cross plate (63) is set to an acute angle.

7. The combined geophysical probe for soil layer according to claim 6, characterized in that: The cross section of the conversion pad (31) is a C-shaped structure, which is suitable for installation and removal.

8. A method for using a combined geophysical probe for soil layers, characterized in that: The combined geophysical probe according to claim 7, wherein the method of using the combined geophysical probe comprises the following steps: Step S101, drilling a hole with the spiral plate probe (5): The combined probe is fixed on the ground of the soil to be tested, and the spiral plate probe (5) is used to drill a hole in the soil until a predetermined test position is reached; Step S103: spiral plate load test: Using the spiral plate probe (5) to perform a spiral plate load test on the surrounding soil; Step S105: Cross-plate shear test: The conversion pad (31) is disassembled, the cross plate probe (6) is pushed out, and the shearing instrument (4) is installed. The shearing instrument (4) includes a horizontally arranged rotating handle (41) and a dial indicator (42) for measuring the deformation of the steel ring; Performing a cross-plate shear test on the soil below the spiral plate probe (5); The shear strength of soil can be calculated using the formula: C u =β·K·C(R y -R g ); Where C u is the shear strength of the soil; β is the reduction coefficient, which is 0.7-0.8 for clay soil and 0.8-0.9 for sandy soil; K is the cross plate constant, in m -2 ; C is the steel ring coefficient, unit is kN / 0.01mm; R y The maximum degree of the dial indicator when shearing is in units of 0.01 mm, measured by the shear instrument; R g It is the maximum degree of the dial indicator during friction, the unit is 0.01mm, and it is measured by a shear instrument.

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