A method for analyzing deep-sea soil lateral survey data

Abstract

The present invention discloses a method for analyzing data of deep-sea soil transverse survey, which belongs to the technical field of deep-sea soil survey, and includes: step 1: analyzing the force of the probe of the survey instrument that is transversely penetrated in saturated clay; step 2: deriving the expression of the hole expansion pressure p based on the hole expansion theory of finite soil; step 3: obtaining the relationship between the transverse cone tip resistance and the undrained shear strength according to step 1 and step 2: step 4: calculating the radius c of the plastic zone by iteration according to the transverse cone tip resistance measured by the probe that is transversely penetrated in actual engineering; step 5: obtaining the undrained shear strength corresponding to the transverse cone tip resistance according to the output radius c. For the transverse survey of shallow soil, the influence of the soil surface on the hole expansion is considered, so that the data analysis result is more in line with the actual working conditions, and the undrained shear strength of the soil is evaluated according to the cone tip resistance obtained by the transverse survey of the probe in the soil, which is convenient for analyzing the physical properties of the soil layer.

Description

Technical Field

[0001] The present invention relates to the technical field of deep sea soil survey, and in particular to a method for analyzing deep sea soil lateral survey data. Background Art

[0002] At present, static penetration testing is mostly used to survey the seabed soil layer. Static penetration testing refers to the use of a pressure device to press a sounding rod with a sounding head into the soil layer, and determine certain basic physical and mechanical properties of the soil layer by measuring parameters such as cone tip resistance and pore water pressure.

[0003] Traditional point-to-vertical surveying devices can survey the seabed soil layer in the longitudinal direction. CN116607493A discloses a seabed transverse detection device and detection method, which can realize the transverse survey of the seabed soil layer and meet the soil survey needs of seabed mining with a wide area and shallow soil layer.

[0004] The data analysis method of traditional point-to-vertical survey equipment is based on the spherical hole expansion theory of infinite soil, ignoring the influence of the soil surface on hole expansion, and is not suitable for the analysis of horizontal survey data. Summary of the invention

[0005] The object of the present invention is to provide a method for analyzing deep-sea soil lateral survey data, which can analyze the data obtained by a lateral survey device.

[0006] As conceived above, the technical solution adopted by the present invention is: a method for analyzing data of deep-sea soil transverse survey, comprising: step 1: analyzing the force of the probe of the survey instrument that is laterally penetrated into the saturated clay to obtain the transverse cone tip resistance The expression is formula (1): , where is the lateral cone tip resistance, kPa; p is the hole expansion pressure, kPa; is the cone angle of the probe; is the cone roughness of the probe; is the undrained shear strength of the soil, kPa.

[0007] Step 2: Based on the hole expansion theory of finite soil, the expression of hole expansion pressure p is derived; the hole where the probe is located expands during the lateral penetration process, and the initial inner radius of the hole is set to , the initial outer radius is , is equal to the buried depth of the probe; the static pressure on the soil is , the soil begins to be in the elastic stage, when the internal pressure changes from When the value increases, the elastic stress and displacement calculation formulas are as follows: (2) to (4), where (2) is , formula (3) is , formula (4) is , where is the radial stress; is the polar coordinate stress; u is the elastic displacement; r is the radius at any position; E is the elastic modulus; is Poisson’s ratio; is the radius of the initial hole and is equal to 0.

[0008] When the soil expands and enters the plastic deformation stage, it obeys the Tresca yield criterion. The yield condition is as follows: , where ; ; ; Combining equations (2), (3) and (5), the calculation formula for the cavity expansion pressure p when the inner surface begins to yield is obtained as equation (6): .

[0009] As the internal pressure continues to increase, a plastic zone is formed on the periphery of the probe, and the periphery of the plastic zone is an elastic zone. The radius of the probe is a, the radius of the plastic zone is c, and the radius of the elastic zone is b, then a<c<b. After the plastic zone is formed on the periphery of the probe, the calculation formula for the stress of the elastic zone is set to equations (19) and (20). Equation (19) is , formula (20) is , Substituting equations (19) and (20) into equation (5) yields equation (21), which is , where A is a constant. According to the elastic-plastic boundary conditions, when the material is in the elastic domain at the boundary of the plastic zone, it is determined by the conditions at the yield point. Therefore, substituting r=c into A, we get formula (22), which is , Substituting equation (22) into equation (19), we get the radial stress in the elastic zone as equation (7), which is , according to formula (7) and (2), we can get Substituting into formula (4), the radial displacement of the elastic zone is obtained as formula (8), which is , substituting equation (22) into equation (20), the polar coordinate stress in the elastic region is obtained as: .

[0010] The equilibrium equation of the plastic zone is (9) , Substitute equation (5) into equation (9) to obtain equation (10) , where B is a constant.

[0011] According to the continuity condition of radial stress at the elastic-plastic boundary, substituting r = c into equations (7) and (10), we obtain equation (11): , substituting equation (11) into equation (10), we get the stress solution equation (12) in the plastic zone: , at r = a, the radial stress in the plastic zone exerts equal magnitude and opposite direction on the hole expansion pressure p of the probe and the hole where the probe is located. Substituting r = a into equation (12), the expression of the hole expansion pressure p is obtained (13): .

[0012] Step 3: Substitute equation (13) into equation (1) and substitute the cone angle of the probe When the angle is equal to 60°, the relationship between the lateral cone tip resistance and the undrained shear strength is obtained as equations (14) and (15). Equation (14) is , formula (15) is , where N is the transverse cone tip coefficient; is the cone roughness of the probe.

[0013] Step 4: Measure the lateral cone tip resistance based on the transverse penetration probe in the actual project , substituted into formula (14), and the radius c of the plastic zone is calculated by iteration; comprising: step 41: the equation for iterative calculation controlled by undrained conditions is formula (16): , where is the initial radial position of soil particles; is the radial position of soil particles after expansion; is the radius of the initial hole; is the radius of the hole after expansion.

[0014] Before the probe penetrates horizontally, the radius of the initial hole is 0. During the penetration of the probe, the hole expands until the radius of the hole is equal to the radius of the probe. The soil particles in the plastic zone move away from the probe. According to the elastic-plastic boundary conditions, equation (16) is transformed into equation (17): , where is the displacement of the plastic boundary.

[0015] At the elastic-plastic boundary, the elastic displacement is equal to the plastic displacement. Substituting r = c into equation (8), the displacement of the plastic boundary is obtained as , and based on Substituting into equation (17) we get equation (18): .

[0016] Step 42: Given the initial value of the radius c of the shaping zone; Step 43: Solve according to equation (14) to obtain Recorded as , according to equation (18), we can obtain Recorded as ; Step 44: If , then output the radius c; otherwise, change the value of c and repeat steps 43 and 44.

[0017] Step 5: Substitute the radius c output in step 44 into equations (14) and (15) to obtain the lateral cone tip resistance Corresponding undrained shear strength .

[0018] Preferably, in step 2, by combining equations (11), (10) and (5), the polar coordinate stress in the plastic zone is obtained as follows: .

[0019] As a preference, the cone angle of the probe Equal to 60°, the cone roughness of the probe When it is equal to 0.5, equation (1) is converted to: .

[0020] As a preferred method, when the radius a of the probe is equal to 0.018 m, the buried depth b0 of the probe is equal to 0.15 m, and the Poisson's ratio =0.50, elastic modulus E=1000kPa, when the soil is subjected to static pressure p0=1.83kPa, according to formula (15) in step 3, we get .

[0021] Preferably, in step 4, a curve of the lateral cone tip resistance versus displacement is measured by a probe that is laterally penetrated in an actual project. The average value of the lateral cone tip resistance is taken according to the curve and substituted into formula (14), and the radius c of the plastic zone is calculated by iteration.

[0022] As a preference, it also includes: step 6: verifying the relationship between the transverse cone tip resistance and the undrained shear strength in step 3, including: step 61: preparing M kinds of kaolin with different strengths, M being a positive integer greater than or equal to 2; step 62: measuring the actual undrained shear strength of the M kinds of kaolin through a cross-plate shear test, and testing multiple transverse positions in the kaolin according to the displacement of the surveying instrument to measure multiple groups of undrained shear strengths; step 63: using the surveying instrument to laterally penetrate the M kinds of kaolin in step 61 to obtain a curve of the transverse cone tip resistance versus displacement, taking the transverse cone tip resistances corresponding to multiple different displacements according to the curve, respectively substituting them into formula (14), and iteratively calculating the radii c of different plastic zones respectively, obtaining multiple undrained shear strengths according to step 5, and obtaining a curve of the undrained shear strength versus displacement; step 64: comparing the undrained shear strength calculated in step 63 with the undrained shear strength measured in the experiment in step 62. If the difference between the two is within the set range, the transverse cone tip resistance in step 3 is Undrained shear strength The relationship meets the requirements.

[0023] Preferably, in step 61, three kinds of kaolin with different strengths are prepared, and in step 62, the actual undrained shear strengths of the three kinds of kaolin are measured by a cross plate shear test to be 0.6 kPa, 1.25 kPa and 1.75 kPa, respectively.

[0024] Beneficial effects of the present invention: The method for analyzing data of deep-sea soil transverse survey proposed in the present invention is based on the pore expansion theory of finite soil, and derives an expression for the pore expansion pressure p. For transverse survey of shallow soil, the influence of the soil surface on pore expansion is taken into account, so that the data analysis results are more in line with actual working conditions. The undrained shear strength of the soil is evaluated based on the cone tip resistance obtained by the transverse survey of the probe in the soil, which is convenient for analyzing the physical properties of the soil layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a force analysis diagram of the probe provided by an embodiment of the present invention.

[0026] Figure 2 It is a schematic diagram of hole expansion of a finite soil body provided by an embodiment of the present invention.

[0027] Figure 3 It is a flow chart of iteratively calculating the radius c of the plastic zone provided by an embodiment of the present invention.

[0028] Figure 4 It is a schematic diagram of the variation of undrained shear strength with displacement obtained by the cross-plate shear test provided in an embodiment of the present invention.

[0029] Figure 5 It is a schematic diagram of the variation of the lateral cone tip resistance with displacement obtained by the surveying instrument provided in an embodiment of the present invention.

[0030] Figure 6 It is the first schematic diagram for comparing undrained shear strength provided by an embodiment of the present invention.

[0031] Figure 7 It is a second schematic diagram for comparing undrained shear strength provided by an embodiment of the present invention.

[0032] Figure 8 It is a third schematic diagram for comparing undrained shear strength provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0034] See also Figures 1 to 8This embodiment provides a method for analyzing transverse survey data of deep-sea soil, which theoretically derives the relationship between transverse cone tip resistance and undrained shear strength, and uses a survey instrument to provide data through transverse detection in the soil, so as to realize the analysis of transverse survey data of deep-sea soil. The survey instrument is an existing transverse detection device, including a probe with a cone tip, which moves transversely at a certain burial depth so that the probe is in full contact with the soil, thereby obtaining the cone tip resistance of the probe.

[0035] The method for analyzing the data of deep-sea soil transverse survey includes: Step 1: Performing force analysis on the probe of the survey instrument that is laterally penetrated into the saturated clay, such as Figure 1 As shown in Figure 1, it is assumed that within the vertical height of the probe, that is, the entire diameter D of the probe, the undrained shear strength of the soil and the variation of the earth pressure along the depth are negligible. The normal stress on the cone tip is replaced by the hole expansion pressure p, and the lateral cone tip resistance is obtained. The expression is formula (1): , where is the lateral cone tip resistance, kPa; p is the hole expansion pressure, kPa; is the cone angle of the probe; is the cone roughness of the probe; is the undrained shear strength of the soil, kPa.

[0036] Step 2: Based on the pore expansion theory of finite soil, the expression of the pore expansion pressure p is derived; the influence of the soil surface on the pore expansion is taken into account, making the data analysis results more consistent with the actual working conditions.

[0037] The probe’s lateral penetration causes the hole in which it is located to expand. The initial inner radius of the hole is set to , the initial outer radius is The static pressure on the soil is The initial outer radius of the hole The buried depth of the probe is usually taken as the distance between the probe location and the water-soil interface. The in-situ pressure of the soil is calculated based on the gravity and water pressure of the soil at the buried depth of the probe. The in-situ pressure of the soil is a commonly used pressure in this field.

[0038] The soil is initially in the elastic stage. When the internal pressure changes from When the value increases, the elastic stress and displacement are calculated as follows: is the radial stress in the elastic region , in formula (3) is the polar stress in the elastic region , u in formula (4) is the elastic displacement , where r is the radius at any position; E is the elastic modulus; is Poisson’s ratio; is the radius of the initial hole and is equal to 0.

[0039] When the soil expands and enters the plastic deformation stage, it obeys the Tresca yield criterion. The Tresca yield criterion is a criterion used in material mechanics to describe the yield behavior of materials. It points out that when the maximum shear stress in the stressed object (particle) reaches a certain constant value, the material will yield. Specifically, the maximum shear stress of the material in the plastic state is a constant value, which depends only on the properties of the material under deformation conditions and has nothing to do with the stress state.

[0040] The yield condition is formula (5): , where ; ; From the above, we can know is the undrained shear strength of the soil, kPa.

[0041] Combining equations (2), (3) and (5), we can obtain the calculation formula of the cavity expansion pressure p when the inner surface begins to yield as equation (6): , from the above, we can know that is the initial inner radius of the hole, is the buried depth of the probe, The soil bears static pressure.

[0042] As the internal pressure continues to increase, a plastic zone is formed on the periphery of the probe, and the periphery of the plastic zone is an elastic zone, such as Figure 2 As shown, the radius of the probe is a, the radius of the plastic zone is c, and the radius of the elastic zone is b, then a<c<b; according to the elastic-plastic boundary conditions, combining equations (2), (4) and (6), the radial stress and displacement of the elastic zone are obtained as equations (7) and (8) respectively.

[0043] In formula (7) is the radial stress in the elastic region , u in formula (8) is the elastic displacement . Among them, the radius c of the plastic zone is unknown, r is the radius at any position; E is the elastic modulus; is Poisson's ratio.

[0044] The equilibrium equation of the plastic zone is formula (9): The equilibrium equation of the plastic zone mainly involves the distribution and change of the internal stress of the object in the plastic state. In plastic mechanics, the equilibrium equation usually refers to the mathematical relationship that the stress generated inside the object due to the external force in the plastic zone must satisfy.

[0045] Substituting equation (5) into equation (9) yields equation (10): , where B is a constant. According to the continuity condition of radial stress at the elastic-plastic boundary, r=c is substituted into equations (7) and (10) to obtain equation (11): , Substituting equation (11) into equation (10), we can obtain the stress solution in the plastic zone.

[0046] Formula (12) , among which is the radial stress in the plastic zone; at r = a, the radial stress in the plastic zone exerts equal magnitude and opposite direction on the hole expansion pressure p of the probe and the hole where the probe is located. Substituting r = a into formula (12), the expression of the hole expansion pressure p is obtained as formula (13): .

[0047] Step 3: Substitute equation (13) into equation (1) and substitute the cone angle of the probe When the angle is equal to 60°, the relationship between the lateral cone tip resistance and the undrained shear strength is obtained as equation (14) and equation (15). Equation (14) , where N is the transverse cone tip coefficient; Formula (15) ,in, is the cone roughness of the probe, and the radius c of the plastic zone is unknown.

[0048] From the above derived equations (14) and (15), it can be seen that in the relationship between the lateral cone tip resistance and the undrained shear strength, there is only one unknown variable, which is the radius c of the plastic zone.

[0049] Step 4: Measure the lateral cone tip resistance based on the transverse penetration probe in the actual project , substituted into formula (14), and the radius c of the plastic zone is calculated by iteration. Specifically, the following steps 41 to 44 are included.

[0050] Step 41: The equation for the iterative calculation under undrained conditions is (16): , where is the initial radial position of soil particles; is the radial position of soil particles after expansion; is the radius of the initial hole; is the radius of the hole after expansion.

[0051] Before the probe penetrates horizontally, the radius of the initial hole is 0. During the penetration of the probe, the hole expands until the radius of the hole is equal to the radius of the probe. The soil particles in the plastic zone move away from the probe. According to the elastic-plastic boundary conditions, equation (16) is transformed into equation (17): , where is the displacement of the plastic boundary.

[0052] At the elastic-plastic boundary, the elastic displacement is equal to the plastic displacement. Substituting r = c into equation (8), the displacement of the plastic boundary is obtained as , and based on Substituting into equation (17), we get equation (18): .

[0053] The radius c of the plastic zone can be calculated by iterative calculation by writing Matlab code.

[0054] Step 42: Give an initial value of the radius c of the shaping zone. Figure 3 , enter the basic parameters in the matlab code, including the cone roughness , Probe cone angle , the radius of the probe a, the buried depth of the probe b0, the static pressure on the soil , elastic modulus E, Poisson's ratio , lateral cone tip resistance And the initial value of the radius c of the given shaping zone.

[0055] Step 43: Solve according to formula (14) to obtain Recorded as , according to formula (18), we can obtain Recorded as Step 44: If , then output the radius c; otherwise, change the value of c and repeat steps 43 and 44.

[0056] Step 5: Substitute the radius c output in step 44 into equations (14) and (15) to obtain the lateral cone tip resistance Corresponding undrained shear strength .

[0057] Among them, the lateral cone tip resistance input in step 42 is It is the transverse cone tip resistance measured by the transversely penetrated probe in actual engineering. In actual engineering, as the transversely penetrated probe moves forward, the transverse cone tip resistance will also change with the change of displacement. Therefore, the curve of the transverse cone tip resistance changing with displacement is obtained. For soil with basically uniform strength, the fluctuation range of the transverse cone tip resistance is not large.

[0058] In this embodiment, in step 4, a curve of the transverse cone tip resistance versus displacement is measured by a probe that is laterally penetrated in an actual project. The average value of the transverse cone tip resistance is taken according to the curve and substituted into equation (14), and the radius c of the plastic zone is calculated by iteration.

[0059] In step 2, after the plastic zone is formed on the periphery of the probe, the calculation formulas for setting the stress in the elastic zone are respectively as follows: and , Substituting equations (19) and (20) into equation (5), we get equation (21) , where A is a constant, which is determined according to the condition that the material is at the yield point when it is in the elastic domain at the boundary of the plastic zone. Therefore, substituting r=c into A, we get formula (22) .

[0060] Substituting equation (22) into equation (19) yields equation (7), and substituting equation (22) into equation (20) yields the polar coordinate stress in the elastic region: .

[0061] According to formula (7) and (2), we can get , substituting into formula (4), the radial displacement of the elastic zone is obtained as formula (8).

[0062] In step 2, by combining equations (11), (10) and (5), the polar coordinate stress in the plastic zone is obtained as: .

[0063] For example, at the cone angle of the probe Equal to 60°, the cone roughness of the probe When it is equal to 0.5, equation (1) is converted to: .

[0064] When the radius a of the probe is equal to 0.018m and the buried depth b0 of the probe is equal to 0.15m, the Poisson's ratio =0.50, elastic modulus E=1000kPa, when the soil is subjected to static pressure p0=1.83kPa, according to formula (15) in step 3, we get .

[0065] For example, in actual engineering, the transverse cone tip resistance measured by the transverse penetration probe is 3.77 kPa, and the radius c of the plastic zone calculated by iteration is equal to 0.156 m, corresponding to N=9.337, and the corresponding undrained shear strength is 0.599 kPa.

[0066] The method for analyzing deep-sea soil transverse survey data also includes: Step 6: verifying the relationship between the transverse cone tip resistance and the undrained shear strength in Step 3. Specifically, the following steps are included.

[0067] Step 61: Prepare M kinds of kaolin with different strengths, where M is a positive integer greater than or equal to 2. In this embodiment, three kinds of kaolin with different strengths are prepared. In other embodiments, two or more kinds of kaolin may be prepared, which is not limited here.

[0068] Step 62: The actual undrained shear strength of the M types of kaolin is measured by a cross-plate shear test. According to the lateral displacement of the survey instrument, multiple lateral positions in the kaolin are tested to measure multiple groups of undrained shear strength. Figure 4 As shown, the multiple undrained shear strengths in each soil are substantially the same. In this embodiment, the actual undrained shear strengths of three kaolins with different strengths were measured by cross plate shear test to be 0.6 kPa, 1.25 kPa and 1.75 kPa respectively.

[0069] The cross-plate shear test is a test that uses a cross-plate to measure the undrained shear strength and sensitivity of saturated soft clay soil. It is a type of in-situ soil test. It presses the cross-plate head into the soft soil at the bottom of the hole through the drill hole and rotates it at a uniform speed. Through a certain measurement system, the torque required for its rotation is measured until the soil is destroyed, and the shear strength of the soil is calculated. The shear strength measured by the cross-plate shear test represents the natural strength of the soil in the hole, that is, the undrained shear strength.

[0070] Step 63: Use a survey instrument to laterally penetrate the M types of kaolin in step 61 to obtain a curve of the lateral cone tip resistance varying with displacement. According to the curve, obtain the lateral cone tip resistances corresponding to multiple different displacements, substitute them into equation (14), and iteratively calculate the radii c of different plastic zones. According to step 5, obtain multiple undrained shear strengths and obtain a curve of the undrained shear strength varying with displacement.

[0071] In this embodiment, the three types of kaolin in step 61 are respectively penetrated laterally by a survey instrument to obtain a curve of the change of the lateral cone tip resistance with the displacement, such as Figure 5 As shown in Figure 2, different curves are obtained for soils of different strengths.

[0072] Take the lateral cone tip resistance corresponding to multiple different displacements in each curve, substitute them into formula (14), and iteratively calculate the radius c of different plastic zones. According to step 5, multiple undrained shear strengths are obtained: , we can get the curves of undrained shear strength of different soils changing with displacement, such as Figures 6 to 8 As shown. Among them, Figure 6 For an undrained soil with a shear strength of 0.6 kPa, Figure 7 For an undrained soil with a shear strength of 1.25 kPa, Figure 8 The corresponding undrained shear strength of the soil is 1.75 kPa.

[0073] Step 64: Compare the undrained shear strength calculated in step 63 with the undrained shear strength measured in step 62. If the difference between the two is within the set range, the transverse cone tip resistance in step 3 is Undrained shear strength The relationship meets the requirements.

[0074] The above embodiments are only to illustrate the basic principles and characteristics of the present invention. The present invention is not limited by the above embodiments. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and modifications, which are within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for analyzing deep-sea soil lateral survey data, characterized in that: include: Step 1: Perform force analysis on the probe of the survey instrument that penetrates horizontally into saturated clay to obtain the lateral cone tip resistance The expression is: （1） In the formula, is the lateral cone tip resistance, kPa; p is the hole expansion pressure, kPa; is the cone angle of the probe; is the cone roughness of the probe; is the undrained shear strength of the soil, kPa; Step 2: Based on the pore expansion theory of finite soil, derive the expression of pore expansion pressure p; The probe’s lateral penetration causes the hole in which it is located to expand. The initial inner radius of the hole is set to , the initial outer radius is , is equal to the buried depth of the probe; the static pressure on the soil is , the soil begins to be in the elastic stage, when the internal pressure changes from When the value increases, the elastic stress and displacement are calculated as follows: （2） （3） （4） In the formula, is the radial stress; is the polar coordinate stress; u is the elastic displacement; r is the radius at any position; E is the elastic modulus; is Poisson’s ratio; is the radius of the initial hole and is equal to 0; When the soil expands and enters the plastic deformation stage, it obeys the Tresca yield criterion, and the yield condition is: （5） In the formula, ; ; ; Combining equations (2), (3) and (5), we can obtain the calculation formula for the cavity expansion pressure p when the inner surface begins to yield: （6） As the internal pressure continues to increase, a plastic zone is formed on the periphery of the probe, and the periphery of the plastic zone is an elastic zone. The radius of the probe is a, the radius of the plastic zone is c, and the radius of the elastic zone is b, then a<c<b; After the plastic zone is formed on the periphery of the probe, the calculation formula for setting the stress in the elastic zone is: （19） （20） Substituting equations (19) and (20) into equation (5), we obtain: （21） Among them, A is a constant. According to the elastic-plastic boundary conditions, when the material is in the elastic domain at the boundary of the plastic zone, it is determined by the conditions at the yield point. Therefore, substituting r=c into A, we get: （22） Substituting equation (22) into equation (19), the radial stress in the elastic zone is obtained as: （7） According to formula (7) and (2), we can get , substituting into formula (4), the radial displacement of the elastic zone is obtained as: （8） Substituting equation (22) into equation (20), the polar coordinate stress in the elastic region is obtained as: ; The equilibrium equation in the plastic zone is: （9） Substituting equation (5) into equation (9), we can obtain: （10） In the formula, B is a constant; According to the continuity condition of radial stress at the elastic-plastic boundary, substituting r = c into equations (7) and (10), we obtain: （11） Substituting equation (11) into equation (10), we obtain the stress solution in the plastic zone: （12） At r = a, the radial stress in the plastic zone exerts the same magnitude and opposite direction on the cavity expansion pressure p of the probe and the hole where the probe is located. Substituting r = a into equation (12), the expression of the cavity expansion pressure p is obtained: （13） Step 3: Substitute equation (13) into equation (1) and substitute the cone angle of the probe Equal to 60°, the relationship between the lateral cone tip resistance and the undrained shear strength is obtained: （14） （15） Where N is the transverse cone tip coefficient; is the cone roughness of the probe; Step 4: Measure the lateral cone tip resistance based on the transverse penetration probe in the actual project , substituted into formula (14), the radius c of the plastic zone is calculated by iteration; including: Step 41: The equation for the undrained condition control iterative calculation is: （16） In the formula, is the initial radial position of soil particles; is the radial position of soil particles after expansion; is the radius of the initial hole; is the radius of the hole after expansion; Before the probe penetrates horizontally, the radius of the initial hole is 0. During the penetration of the probe, the hole expands until the radius of the hole is equal to the radius of the probe. The soil particles in the plastic zone move away from the probe. According to the elastic-plastic boundary conditions, equation (16) is converted to: （17） In the formula, is the displacement of the plastic boundary; At the elastic-plastic boundary, the elastic displacement is equal to the plastic displacement. Substituting r = c into equation (8), the displacement of the plastic boundary is obtained as , and based on Substituting into formula (17) we get: （18） Step 42: giving an initial value of the radius c of the shaping zone; Step 43: Solve according to formula (14) to obtain Recorded as , according to equation (18), we can obtain Recorded as ; Step 44: If , then output the radius c; otherwise, change the value of c and repeat steps 43 and 44; Step 5: Substitute the radius c output in step 44 into equations (14) and (15) to obtain the lateral cone tip resistance Corresponding undrained shear strength .

2. The deep sea soil lateral survey data analysis method according to claim 1, characterized in that: In step 2, by combining equations (11), (10) and (5), the polar coordinate stress in the plastic zone is obtained as: .

3. The deep sea soil lateral survey data analysis method according to claim 1, characterized in that: The cone angle of the probe Equal to 60°, the cone roughness of the probe When it is equal to 0.5, equation (1) is converted to: .

4. The method for analyzing deep sea soil lateral survey data according to claim 3, characterized in that: When the radius a of the probe is equal to 0.018m and the buried depth b0 of the probe is equal to 0.15m, the Poisson's ratio =0.50, elastic modulus E=1000kPa, when the soil is subjected to static pressure p0=1.83kPa, according to formula (15) in step 3, we get .

5. The deep sea soil lateral survey data analysis method according to claim 1, characterized in that: In step 4, the curve of the transverse cone tip resistance versus displacement is measured by the probe that is laterally penetrated in the actual project. The average value of the transverse cone tip resistance is taken according to the curve and substituted into equation (14), and the radius c of the plastic zone is calculated by iteration.

6. The method for analyzing deep sea soil lateral survey data according to any one of claims 1 to 5, characterized in that: Also includes: Step 6: Verify the relationship between the lateral cone tip resistance and the undrained shear strength in step 3, including: Step 61: preparing M kinds of kaolin with different strengths, where M is a positive integer greater than or equal to 2; Step 62: measuring the actual undrained shear strength of the M types of kaolin by a cross-plate shear test, and performing tests at multiple transverse positions in the kaolin according to the displacement of the survey instrument to measure multiple groups of undrained shear strength; Step 63: Use a survey instrument to laterally penetrate the M types of kaolin in step 61 to obtain a curve of lateral cone tip resistance versus displacement. Take multiple lateral cone tip resistances corresponding to different displacements according to the curve, substitute them into equation (14), and iteratively calculate the radii c of different plastic zones. According to step 5, obtain multiple undrained shear strengths and obtain a curve of undrained shear strength versus displacement. Step 64: Compare the undrained shear strength calculated in step 63 with the undrained shear strength measured in step 62. If the difference between the two is within the set range, the transverse cone tip resistance in step 3 is Undrained shear strength The relationship meets the requirements.

7. The method for analyzing deep sea soil lateral survey data according to claim 6, characterized in that: In step 61, three kinds of kaolin with different strengths are prepared. In step 62, the actual undrained shear strengths of the three kinds of kaolin are measured by a cross plate shear test and are found to be 0.6 kPa, 1.25 kPa and 1.75 kPa, respectively.

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