A spherical static penetration test device and method for simultaneously measuring the strength and sensitivity of soft clay

Abstract

The invention provides a spherical static penetration test device and method for simultaneously measuring the strength and sensitivity of soft clay. Compared with a traditional cross-plate shear test, the device and method can obtain continuous undrained shear strength of in-situ soft clay; compared with a traditional spherical static penetration test, the device and method can simultaneously measure the undrained shear strength of in-situ soft clay, the undrained shear strength of remodeled soft clay and the sensitivity of soft clay by only one penetration process, the operation is simple, and the test efficiency is greatly improved; at the same time, the undrained shear strength of remodeled soil can be measured at any time by penetration and cross-plate shear at any time, and the undrained shear strength of remodeled soft clay and the sensitivity of soft clay can be obtained by reducing the cross-plate shear test interval, thereby taking into account the advantages of the cross-plate shear test and the spherical static penetration test.

Description

Technical Field

[0001] The present invention relates to the field of testing the mechanical properties of soft clay, and more particularly to a spherical static penetration testing device and method for simultaneously measuring the strength and sensitivity of soft clay. Background Art

[0002] High-sensitivity, low-strength soft clay is widely distributed in the East my country Sea. The traditional exploration method uses drilling sampling and then conducts indoor tests on soil samples to evaluate the strength and sensitivity of soft clay. The accuracy of indoor tests is heavily dependent on the quality of drilling sampling. Due to the influence of wind, waves and currents during offshore exploration operations, and the long transportation distance and time, the soil samples are disturbed to a greater extent. High-sensitivity, low-strength soft clay is affected by the disturbance. The traditional exploration sampling-indoor test method will result in the soft clay strength s u Seriously underestimated, resulting in sensitivity S t (Sensitivity S t = undisturbed soil strength s u / Fully remolded soil strength u ') The measurement results are wrong. The sensitivity of soft clay is often used in pile driving analysis. Underestimation of the sensitivity parameter may lead to overestimation of the pile driving hammer energy, resulting in pile slippage and possible serious safety accidents.

[0003] In-situ testing technology in marine new energy exploration has less disturbance on the soil and can obtain more accurate in-situ soft clay strength s u The spherical static penetration test is suitable for soft clay with a strength of 0 to 50 kPa. The spherical probe is statically penetrated into the soft clay and the strength of the soft clay is interpreted by measuring the reaction force of the spherical probe. Its advantage is that it can obtain continuous soft clay strength, but it cannot simultaneously obtain the reshaped soft clay strength, which is used to calculate the sensitivity of soft clay.

[0004] By establishing a spherical static penetration test device and method that can simultaneously measure the strength and sensitivity of soft clay, a more accurate sensitivity of soft clay can be obtained, while greatly improving the efficiency of in-situ testing, which has important engineering significance. Summary of the invention

[0005] The first purpose of the present invention is to address the deficiencies in the prior art and to provide a spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay, which can simultaneously obtain accurate in-situ strength of soft clay, strength and sensitivity parameters of reshaped soft clay.

[0006] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0007] A spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay comprises a spherical probe, an annular permeable stone, an external thread of the spherical probe, a lower sleeve, a cross plate shaft, a cross plate head, an upper sleeve, a pore pressure sensor, a sensor data line, a lower internal thread of the lower sleeve, an upper internal thread of the lower sleeve, an axial force sensor, an external thread of the axial force sensor, a lower protective ring layer, an upper protective ring layer, a torque sensor, a rotary drive device, a drive device connecting line, a drive device controller, and a data collector.

[0008] The spherical probe has an annular hollow area in the middle, in which a pore pressure sensor is inlaid, and the pore pressure sensor is wrapped with an annular permeable stone; the top of the spherical probe has an external thread of the spherical probe; the bottom of the lower sleeve has a lower sleeve lower internal thread and a lower sleeve upper internal thread, and the lower sleeve has a lower protective ring layer inside; the spherical probe and the lower sleeve can be connected as a whole through the spherical probe external thread and the lower sleeve lower internal thread; the axial force sensor has an axial force sensor external thread, which can be connected as a whole with the lower sleeve upper internal thread of the lower sleeve; a cross plate head is welded in the middle of the cross plate shaft; the upper sleeve has an upper protective ring layer; the cross plate shaft can be just placed in the lower protective ring layer and the upper protective ring layer; the torque sensor is connected to the cross shaft and the rotary drive device; the rotary drive device is welded on the cross plate shaft, and is connected to the drive device controller through the drive device connecting line; the sensor data line connects the pore pressure sensor, the axial force sensor and the torque sensor, and finally connects to the data acquisition device.

[0009] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0010] As a preferred technical solution of the present invention: the lower protective ring layer and the upper protective ring layer are hollowed out inside to just accommodate the cross plate shaft rod, so as to ensure that the cross plate shaft rod will not tilt during the rotation process.

[0011] As a preferred technical solution of the present invention: the lower protective ring layer and the upper protective ring layer can be made of Teflon material, and the interface friction coefficient is low, which can ensure that the cross plate shaft is less affected by the lower protective ring layer and the upper protective ring layer during rotation, thereby reducing the torque test error.

[0012] As a preferred technical solution of the present invention: the torque sensor is directly welded to the cross plate shaft or the torque sensor adopts a strain gauge sensor, which is attached to the cross plate shaft by strong glue, and then the torque exerted on the cross plate shaft is calculated by the measured strain.

[0013] As a preferred technical solution of the present invention: the spherical probe, the axial force sensor, the lower protective ring layer, the cross plate shaft rod and the upper protective ring layer are all hollowed out in the middle to allow the sensor data line to pass through.

[0014] Another object of the present invention is to provide a method for performing a penetration test based on the spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay as described above, in view of the deficiency that the existing spherical static penetration test device cannot simultaneously measure the strength of remolded soft clay.

[0015] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0016] A method for performing a penetration test based on the spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay as described above comprises the following steps:

[0017] Step 1: Install the equipment:

[0018] Step 101: Pass the sensor data line of the spherical probe through the lower sleeve, and connect the spherical probe external thread of the spherical probe with the lower sleeve through the lower internal thread of the lower sleeve;

[0019] Step 102: Pass the sensor data line through the axial force sensor, and install the axial force sensor on the lower sleeve through the external thread of the axial force sensor;

[0020] Step 103: Pass the sensor data line through the lower protective ring layer and the cross plate shaft rod, place the lower protective ring layer in the lower sleeve, and install the cross plate shaft rod in the lower protective ring layer;

[0021] Step 104: Place the upper protective ring layer in the upper sleeve and sleeve it on the outer ring of the cross plate shaft rod, and connect the sensor data line to the data collector;

[0022] Step 2: Spherical probe penetration:

[0023] Step 201: Turn on the data logger, vertically and uniformly penetrate the test device formed in step 1 into the soft clay, and record the probe resistance q obtained by the axial force sensor. m , pore pressure u2 measured by pore pressure sensor;

[0024] Step 202: Calculate the corrected spherical probe resistance:

[0025] q ball =q m -[σ v0 -u2*(1-α)]·A s / A p

[0026] Where: q ball is the modified spherical probe resistance; q m is the measured spherical probe resistance; σ v0 is the total vertical stress of the soil at the measurement location; u2 is the measured pore pressure; α is the area ratio, which is generally around 0.75; A sis the cross-sectional area of ​​the sleeve; A p is the cross-sectional area of ​​the spherical probe.

[0027] Step 203: Calculate the undrained shear strength of the original soft clay:

[0028] s u =q ball / N ball

[0029] Where: s u is the undrained shear strength of original soft clay; N ball It is an empirical coefficient, which can generally be taken as 10.5.

[0030] Step 3: Cross-plate shearing to reshape soft clay:

[0031] Step 301: When the testing device reaches a specified depth, the penetration is stopped. At this time, the soft clay at the cross plate head is reshaped by the penetration of the spherical probe;

[0032] Step 302: Turn on the driving device controller, control the cross-plate shaft to drive the cross-plate head to shear the soft clay at a rate of 0.1° / s, and measure the torque T at the peak value;

[0033] Step 303: Calculate the undrained shear strength of remolded soft clay:

[0034]

[0035] Where: s u ′ is the undrained shear strength of remolded soft clay; D is the cross-plate head diameter; H is the cross-plate head height; T is the measured peak torque.

[0036] Step 304: Calculate the sensitivity of soft clay:

[0037]

[0038] Step 4: Perform the penetration process of step 2 again to the next soft clay depth (which can be about 0.1m). After reaching the test depth, stop and perform step 3 again to obtain the continuous in-situ undrained shear strength of soft clay. The intermittently measured undrained shear strength of reshaped soft clay is used to characterize the undrained shear strength of reshaped soft clay with a length of 0.1m, and the continuous soft clay sensitivity parameter can be obtained.

[0039] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0040] As a preferred technical solution of the present invention: in step 103 and step 104, silicone grease can be applied on the outside of the cross plate shaft to reduce the friction between the cross plate shaft and the lower protective ring layer and the upper protective ring layer, so that the torque during the rotation of the cross plate shaft is only generated by the reaction force of the soft clay when the cross plate rotates, thereby improving the test accuracy.

[0041] As a preferred technical solution of the present invention: in step 201, the test device formed can be connected by adding an external thread to the outer ring of the upper sleeve, using a probe rod with an inner diameter the same as the outer diameter of the upper sleeve, and the test device is penetrated into the soft clay through a uniform and stable reaction force static pressure device.

[0042] As a preferred technical solution of the present invention: in step 301, the cross-sectional area of ​​the spherical probe is much larger than the cross-sectional area of ​​the sleeve, which can be 20:1. For soft clay, the penetration of the spherical probe can cause structural destruction of the soft clay and exhibit clay flow characteristics, and flow to the vicinity of the cross-plate head, completely wrapping the cross-plate head, providing necessary conditions for the smooth implementation of the shearing of the cross plate in step 302.

[0043] As a preferred technical solution of the present invention: in step 302, the soft clay is sheared by rotating the cross plate, and the resistance torque of the reshaped soft clay can be directly measured, and then the undrained shear strength is directly calculated through step 303, thereby realizing the direct measurement of the undrained shear strength of the reshaped soil during the single spherical probe penetration process, and the direct acquisition of the sensitivity of the soft clay in step 304.

[0044] The present invention provides a spherical static penetration test device and method that can simultaneously measure the strength and sensitivity of soft clay, which has the following beneficial effects:

[0045] 1) The lower and upper protective rings are hollowed out to accommodate the cross plate shaft, which ensures that the cross plate shaft will not tilt during rotation. The lower and upper protective rings can be made of Teflon material. At the same time, silicone grease is applied to the outside of the cross plate shaft to minimize the friction during the rotation of the cross plate shaft, ensuring that the torque is generated by the reaction force of the soft clay near the cross plate head, which greatly improves the test accuracy.

[0046] 2) The cross-sectional area of ​​the spherical probe is much larger than that of the sleeve. After the spherical probe is penetrated, it can cause structural damage to the soft clay and present clay flow characteristics, and flow to the vicinity of the cross-plate head, completely wrapping the cross-plate head, providing the necessary conditions for the smooth implementation of subsequent cross-plate shearing.

[0047] 3) This test device is used to measure the mechanical properties of soft clay. Unlike the traditional cross-plate shear test, it can obtain the continuous undrained shear strength of in-situ soft clay. Generally, the traditional cross-plate shear test has a basic test spacing (usually 0.5m) to ensure that the undrained shear strength of the original soil can be measured;

[0048] 4) The mechanical properties of soft clay are measured by this test device. Unlike the traditional spherical static penetration test, the undrained shear strength of the in-situ soft clay, the undrained shear strength of the reshaped soft clay and the sensitivity of the soft clay can be measured simultaneously with only one penetration process. The operation is simple and the test efficiency is greatly improved.

[0049] 5) This test device is used to measure the mechanical properties of soft clay. The undrained shear strength of the remolded soil can be measured at any time by penetration and cross-plate shear test. Unlike the traditional cross-plate shear test, there is no basic test spacing (generally 0.5m). Therefore, by reducing the cross-plate shear test spacing, a more continuous undrained shear strength of the remolded soft clay and the sensitivity of the soft clay can be obtained.

[0050] In summary, the present invention has a simple structure and a reasonable design. Compared with the traditional cross-plate shear test, the present invention can obtain the continuous undrained shear strength of in-situ soft clay; compared with the traditional spherical static penetration test, only one penetration process can be used to simultaneously measure the undrained shear strength of in-situ soft clay, the undrained shear strength of reshaped soft clay and the sensitivity of soft clay, the operation is simple, and the test efficiency is greatly improved; the undrained shear strength of reshaped soil can be measured at any time by penetration and cross-plate shear at any time. Compared with the traditional cross-plate shear test, there is no most basic test spacing (generally 0.5m), therefore, by reducing the cross-plate shear test spacing, a relatively continuous undrained shear strength of reshaped soft clay and the sensitivity of soft clay can be obtained, taking into account the advantages of the cross-plate shear test and the spherical static penetration test. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a front view of a spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay provided by the present invention.

[0052] Figure 2 This is the front view of the spherical probe.

[0053] Figure 3 for Figure 1 a-a' cross-section.

[0054] Figure 4 for Figure 3 b-b' section view.

[0055] Figure 5 for Figure 3c-c' section view. DETAILED DESCRIPTION

[0056] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0057] like Figure 1 to Figure 3 As shown, a spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay comprises a spherical probe 1, an annular permeable stone 2, an external thread of the spherical probe 3, a lower sleeve 4, a cross plate shaft 5, a cross plate head 6, an upper sleeve 7, a pore pressure sensor 8, a sensor data line 9, a lower internal thread 10 of the lower sleeve, an upper internal thread 11 of the lower sleeve, an axial force sensor 12, an external thread 13 of the axial force sensor, a lower protective ring layer 14, an upper protective ring layer 15, a torque sensor 16, a rotation drive device 17, a drive device connecting line 18, a drive device controller 19, and a data collector 20.

[0058] The spherical probe 1 has an annular hollow area in the middle, inlaid with a pore pressure sensor 8, and the pore pressure sensor 8 is wrapped with an annular permeable stone 2; the top of the spherical probe 1 has a spherical probe external thread 3; the bottom of the lower sleeve 4 has a lower sleeve lower internal thread 10 and a lower sleeve upper internal thread 11, and the lower sleeve 4 has a lower protective ring layer 14; the spherical probe 1 and the lower sleeve 4 can be connected into one through the spherical probe external thread 3 and the lower sleeve lower internal thread 10; the axial force sensor 12 has an axial force sensor external thread 13, which can be connected with the lower sleeve upper internal thread 11 of the lower sleeve 4. The groove 11 is connected into one body; a cross plate head 6 is welded in the middle of the cross plate shaft 5; the upper sleeve 7 has an upper protective ring layer 15; the cross plate shaft 5 can be placed just in the lower protective ring layer 14 and the upper protective ring layer 15; the torque sensor 16 is connected to the cross plate shaft 5 and the rotation drive device 17; the rotation drive device 17 is welded to the cross plate shaft 5, and is connected to the drive device controller 19 through the drive device connecting line 18; the sensor data line 9 is connected to the pore pressure sensor 8, the axial force sensor 12 and the torque sensor 16, and finally connected to the data acquisition device 20.

[0059] The lower protective ring layer 14 and the upper protective ring layer 15 are hollowed out inside to just accommodate the cross plate shaft rod 5, so as to ensure that the cross plate shaft rod 5 will not tilt during the rotation process.

[0060] The lower protective ring layer 14 and the upper protective ring layer 15 can be made of Teflon material, and the interface friction coefficient is low, which can ensure that the cross plate shaft 5 is less affected by the lower protective ring layer 14 and the upper protective ring layer 15 during rotation, thereby reducing the test error of the torque.

[0061] The torque sensor 16 can be directly welded to the cross plate shaft 5, or a strain gauge sensor can be used. The strain gauge sensor is attached to the cross plate shaft 5 by strong glue, and the torque on the cross plate shaft 5 is calculated by the measured strain.

[0062] The spherical probe 1, the axial force sensor 12, the lower protective ring layer 14, the cross plate shaft 5 and the upper protective ring layer 15 are all hollowed out in the middle, so that the sensor data line 9 can pass through.

[0063] A spherical static penetration test method for simultaneously measuring the strength and sensitivity of soft clay comprises the following steps:

[0064] Step 1: Install the equipment:

[0065] Step 101: Pass the sensor data line 9 of the spherical probe 1 through the lower sleeve 4, and connect the spherical probe external thread 3 of the spherical probe 1 with the lower sleeve 4 through the lower sleeve internal thread 10;

[0066] Step 102: Pass the sensor data line 9 through the axial force sensor 12, and install the axial force sensor 12 on the lower sleeve 4 through the axial force sensor external thread 13;

[0067] Step 103: Pass the sensor data line 9 through the lower protective ring layer 14 and the cross plate shaft rod 5, place the lower protective ring layer 14 in the lower sleeve 4, and install the cross plate shaft rod 5 in the lower protective ring layer 14;

[0068] Step 104: Place the upper protective ring layer 15 in the upper sleeve 7 and sleeve it on the outer ring of the cross plate shaft 5, and connect the sensor data line 9 to the data collector 20;

[0069] Step 2: Spherical probe penetration:

[0070] Step 201: Turn on the data collector 20, vertically and uniformly penetrate the test device formed in step 1 into the soft clay, and record the probe resistance q obtained by the axial force sensor. m , pore pressure u2 measured by pore pressure sensor 8;

[0071] Step 202: Calculate the corrected spherical probe resistance:

[0072] q ball =q m -[σ v0 -u2*(1-α)]·A s / A p

[0073] Where: q ball is the modified spherical probe resistance; q m is the measured spherical probe resistance; σ v0 is the total vertical stress of the soil at the measurement location; u2 is the measured pore pressure; α is the area ratio, which is generally around 0.75; A s is the cross-sectional area of ​​the sleeve; A p is the cross-sectional area of ​​the spherical probe.

[0074] Step 203: Calculate the undrained shear strength of the original soft clay:

[0075] s u =q ball / N ball

[0076] Where: s u is the undrained shear strength of original soft clay; N ball It is an empirical coefficient, which can generally be taken as 10.5.

[0077] Step 3: Cross-plate shearing to reshape soft clay:

[0078] Step 301: When the testing device reaches a specified depth, the penetration is stopped. At this time, the soft clay at the cross plate head 6 is in a reshaped state due to the penetration of the spherical probe 1;

[0079] Step 302: Turn on the driving device controller 19, control the cross-plate shaft 5 to drive the cross-plate head 6 to shear the soft clay at a rate of 0.1° / s, and measure the torque T at the peak value;

[0080] Step 303: Calculate the undrained shear strength of remolded soft clay:

[0081]

[0082] Where: s u ' is the undrained shear strength of reshaped soft clay; D is the cross-plate head diameter; H is the cross-plate head height; T is the measured peak torque.

[0083] Step 304: Calculate the sensitivity of soft clay:

[0084]

[0085] Step 4: Perform the penetration process of step 2 again to the next soft clay depth (which can be about 0.1m). After reaching the test depth, stop and perform step 3 again to obtain the continuous in-situ undrained shear strength of soft clay. The intermittently measured undrained shear strength of reshaped soft clay is used to characterize the undrained shear strength of reshaped soft clay with a length of 0.1m, and the continuous soft clay sensitivity parameter can be obtained.

[0086] In step 103 and / or step 104, silicone grease is applied to the outer side of the cross plate shaft to reduce the friction between the cross plate shaft and the lower protective ring layer and the upper protective ring layer, so that the torque during the rotation of the cross plate shaft is only generated by the reaction force of the soft clay on the rotation of the cross plate, thereby improving the test accuracy.

[0087] In step 201, the test device formed can be connected by adding external threads to the outer ring of the upper sleeve, using a probe rod with an inner diameter the same as the outer diameter of the upper sleeve, and the test device is penetrated into the soft clay through a uniform and stable reaction static pressure device.

[0088] In step 301, the cross-sectional area of ​​the spherical probe is much larger than the cross-sectional area of ​​the sleeve, for example, in this embodiment, it is 20:1. For soft clay, after the spherical probe is penetrated, the soft clay may be structurally destroyed and exhibit clay flow characteristics, and flow to the vicinity of the cross plate head, completely wrapping the cross plate head, providing the necessary conditions for the smooth implementation of the shearing of the cross plate in step 302.

[0089] In step 302, the soft clay is sheared by rotating the cross plate, and the resistance torque of the reshaped soft clay can be directly measured, and then the undrained shear strength can be directly calculated in step 303, realizing the direct measurement of the undrained shear strength of the reshaped soil during a single spherical probe penetration process, and the direct acquisition of the sensitivity of the soft clay in step 304.

[0090] The above-mentioned specific implementation methods are used to explain the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay, characterized in that: The spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay comprises a spherical probe, an annular permeable stone, an external thread of the spherical probe, a lower sleeve, a cross plate shaft, a cross plate head, an upper sleeve, a pore pressure sensor, a sensor data line, a lower internal thread of the lower sleeve, an upper internal thread of the lower sleeve, an axial force sensor, an external thread of the axial force sensor, a lower protective ring layer, an upper protective ring layer, a torque sensor, a rotation drive device, a drive device connecting line, a drive device controller, and a data collector; The spherical probe has an annular hollow area in the middle, in which a pore pressure sensor is inlaid, and the pore pressure sensor is wrapped with an annular permeable stone; The top of the spherical probe is provided with a spherical probe external thread; The bottom of the lower sleeve has a lower sleeve lower internal thread and a lower sleeve upper internal thread, and the interior of the lower sleeve has a lower protective ring layer; The spherical probe and the lower sleeve are connected as one body through the external thread of the spherical probe and the internal thread of the lower sleeve; The axial force sensor has an axial force sensor external thread, which is connected to the internal thread on the lower sleeve of the lower sleeve as a whole; A cross plate head is welded to the middle of the cross plate shaft; The upper sleeve has an upper protective ring layer; The cross plate shaft is just placed in the lower protective ring layer and the upper protective ring layer; The torque sensor is connected to the cross shaft and the rotation drive device; The rotary drive device is welded to the cross plate shaft and connected to the drive device controller via a drive device connecting line; The sensor data line is connected to the pore pressure sensor, the axial force sensor and the torque sensor, and finally connected to the data collector; The cross-sectional area of ​​the spherical probe is larger than that of the sleeve, so that for soft clay, after the spherical probe penetrates, the soft clay is structurally destroyed and exhibits clay flow characteristics, and flows to the cross-plate head, completely wrapping the cross-plate head.

2. The spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay according to claim 1, characterized in that: The lower protective ring layer and the upper protective ring layer are hollowed out to just accommodate the cross plate shaft rod.

3. The spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay according to claim 1, characterized in that: The lower protective ring layer and the upper protective ring layer are made of Teflon material.

4. The spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay according to claim 1, characterized in that: The torque sensor is directly welded to the cross plate shaft or the torque sensor adopts a strain gauge sensor, which is attached to the cross plate shaft by strong glue, and the torque applied to the cross plate shaft is calculated by the measured strain.

5. The spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay according to claim 1, characterized in that: The spherical probe, the axial force sensor, the lower protective ring layer, the cross plate shaft rod and the upper protective ring layer are all hollowed out in the middle to allow the sensor data line to pass through.

6. A method for performing a penetration test using the spherical static penetration test device for simultaneously measuring the strength and sensitivity of soft clay as claimed in claim 1, characterized in that: The method comprises the following steps: Step 1: Install the equipment to form a test device: Step 101: Pass the sensor data line of the spherical probe through the lower sleeve, and connect the spherical probe external thread of the spherical probe to the lower sleeve through the lower internal thread of the lower sleeve; Step 102: Pass the sensor data line through the axial force sensor, and install the axial force sensor on the lower sleeve through the external thread of the axial force sensor; Step 103: Pass the sensor data line through the lower protective ring layer and the cross plate shaft rod, place the lower protective ring layer in the lower sleeve, and install the cross plate shaft rod in the lower protective ring layer; Step 104: Place the upper protective ring layer in the upper sleeve and sleeve it on the outer ring of the cross plate shaft rod, and connect the sensor data line to the data acquisition device; Step 2: Spherical probe penetration: Step 201: Turn on the data logger, vertically and uniformly penetrate the test device formed in step 1 into the soft clay, and record the probe resistance q obtained by the axial force sensor. m , pore pressure u2 measured by pore pressure sensor; Step 202: Calculate the corrected spherical probe resistance: q ball =q m -[σ v0 -u2*(1-α)]·A s / A p Where: q ball is the modified spherical probe resistance; q m is the measured spherical probe resistance; σ v0 is the total vertical stress of the soil at the measurement location; u2 is the measured pore pressure; α is the area ratio, which is 0.75; A s is the cross-sectional area of ​​the sleeve; A p is the cross-sectional area of ​​the spherical probe; Step 203: Calculate the undrained shear strength of the original soft clay: s u =q ball / N ball Where: s u is the undrained shear strength of original soft clay; N ball is the empirical coefficient, and its value is 10.5; Step 3: Cross-plate shearing to reshape soft clay: Step 301: When the testing device reaches a specified depth, the penetration is stopped. At this time, the soft clay at the cross plate head is reshaped by the penetration of the spherical probe; Step 302: Turn on the driving device controller, control the cross-plate shaft to drive the cross-plate head to shear the soft clay at a rate of 0.1° / s, and measure the torque T at the peak value; Step 303: Calculate the undrained shear strength of remolded soft clay: Where: s u ' is the undrained shear strength of reshaped soft clay; D is the cross plate head diameter; H is the cross plate head height; T is the measured peak torque; Step 304: Calculate the sensitivity of soft clay: Step 4: Perform the penetration process of step 2 again to the next soft clay depth. After reaching the test depth, stop and perform step 3 again to obtain the continuous in-situ undrained shear strength of soft clay. The intermittently measured undrained shear strength of reshaped soft clay is used to characterize the undrained shear strength of reshaped soft clay with a length of 0.1 m, and the continuous soft clay sensitivity parameter can be obtained.

7. The penetration test method according to claim 6, characterized in that: In step 103 and / or step 104, silicone grease is applied to the outer side of the cross plate shaft to reduce the friction between the cross plate shaft and the lower protective ring layer and the upper protective ring layer, so that the torque during the rotation of the cross plate shaft is only generated by the reaction force of the soft clay on the rotation of the cross plate, thereby improving the test accuracy.

8. The penetration test method according to claim 6, characterized in that: In step 201, the test device is formed by adding external threads to the outer ring of the upper sleeve, connecting with a probe rod having an inner diameter the same as the outer diameter of the upper sleeve, and penetrating the test device into the soft clay through a uniform and stable reaction static pressure device.

9. The penetration test method according to claim 6, characterized in that: In step 302, the soft clay is sheared by rotating the cross plate, and the resistance torque of the reshaped soft clay is directly measured, and then the undrained shear strength is directly calculated in step 303, which realizes the direct measurement of the undrained shear strength of the reshaped soil during the single spherical probe penetration process, and the direct acquisition of the sensitivity of the soft clay in step 304.

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