In-situ testing device and method for marine super-soft soil

Abstract

The invention discloses an in-situ testing device for marine supersoft soil, including a spherical sounding assembly and a static penetration assembly. The spherical sounding assembly includes a data acquisition analyzer, an air pressure source, a connected spherical probe and a hollow probe rod. The spherical probe is provided with a ball-shaped resistance sensor, a side wall friction resistance sensor, a side expansion membrane and a pore water pressure sensor in sequence from the bottom to the top; the static penetration assembly includes a base for supporting the spherical sounding assembly and a penetration rate control box for controlling the movement of the spherical probe; the data acquisition analyzer calculates the mechanical properties of marine supersoft soil according to the data collected during the penetration of the spherical probe. By making full use of the advantages of the spherical probe structural design, the high sensitivity, undrained shear strength and side expansion modulus of supersoft soil can be measured efficiently, at low cost and with high accuracy, solving the limitation of insufficient applicability of traditional marine in-situ testing technology.

Description

Technical Field

[0001] The invention relates to an in-situ testing device and method for marine super-soft soil. Background Art

[0002] The ocean is rich in resources. How to efficiently and reasonably develop marine resources to promote the construction of ecological civilization has become one of the important problems that need to be solved urgently. The utilization of marine resources is inseparable from engineering construction. From traditional land reclamation and port projects to cross-sea bridges, offshore oil and gas drilling platforms, and seabed mineral mining, marine engineering construction has continued to develop towards the deep sea and the open sea, making the design and construction of marine engineering increasingly difficult, especially for the acquisition of relevant parameters of marine engineering design. New requirements have been put forward.

[0003] Among them, there are a large number of marine sedimentary super-soft soils in deep sea and offshore areas. These super-soft soils have the characteristics of high sensitivity, high natural water content and extremely low strength. These inherent characteristics make:

[0004] First, it is difficult to obtain satisfactory results by methods such as drilling sampling and indoor testing, and the disturbances in the field sampling and indoor sample preparation process will cause great changes in the microstructure and shear strength of highly sensitive soft soil.

[0005] Second, the native stress state of marine supersoft soil is complex, and the existing experimental conditions are difficult to simulate realistically, which leads to large differences between the test results and the actual properties.

[0006] That is, traditional geotechnical engineering testing technology is gradually unable to meet the needs of engineering investigation. With the continuous development of in-situ testing technology, scholars will insert probes with various sensors into the soil at a certain rate, continuously read the sensor test data, and then calculate various soil property parameters. This static penetration technology has the characteristics of "semi-disturbance", fast, and continuous, and has been widely used in various geotechnical engineering construction. However, the test accuracy of ordinary conical static penetration test equipment continues to decrease in the context of high stress environment, high sensitivity, and low-strength soft soil in the ocean, and it is difficult to meet the needs of the development of marine engineering construction.

[0007] In response to these problems, the international community has developed a full-flow probe that increases the soil contact area while allowing the flowing or quasi-flowing soft soil to surround the probe, thereby obtaining engineering properties such as strength of marine super-soft soil. The spherical probe is the most representative of the full-flow probes. The spherical structure design can perfectly achieve the "soil flow" surrounding, and the strength index test results are more accurate, but for the high sensitivity of marine super-soft soil (S t >8) undrained shear strength of super soft soil (undrained shear strength c uHowever, the test of deformation indicators (such as lateral expansion modulus) with a value less than 10 kPa is helpless, and the conversion results obtained using existing empirical formulas have poor applicability and are difficult to promote. Summary of the invention

[0008] In view of the above problems, the present invention provides an in-situ testing device and method for marine supersoft soil, which fully utilizes the advantages of the spherical probe structure design, transforms the traditional testing device, and develops an in-situ testing device suitable for marine engineering construction in deep sea and offshore areas. The in-situ testing device can efficiently, low-cost and highly accurately measure the high sensitivity, undrained shear strength and lateral expansion modulus of supersoft soil, which solves the limitation of insufficient applicability of traditional marine in-situ testing technology, saves social resources, and has good economic benefits and engineering application prospects.

[0009] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0010] An in-situ testing device for marine super-soft soil, comprising a spherical penetration component and a static penetration component:

[0011] The spherical sounding assembly includes a data acquisition analyzer, an air pressure source, a connected spherical probe and a hollow probe rod. The spherical probe is provided with a ball-shaped resistance sensor, a side wall friction resistance sensor, a side expansion membrane and a pore water pressure sensor in sequence from the bottom to the top. The ball-shaped resistance sensor, the side wall friction resistance sensor and the pore water pressure sensor are connected to the data acquisition analyzer through a sounding signal data line. The side expansion membrane is connected to the data acquisition analyzer through a membrane signal data line and an air pressure pipeline respectively. The air pressure pipeline is connected to the air pressure source and is provided with an exhaust valve. The air pressure source applies gas pressure to the side expansion membrane through the air pressure pipeline.

[0012] The static penetration assembly includes a base for supporting the spherical sounding assembly and a penetration rate control box for controlling the movement of the spherical probe;

[0013] The data acquisition and analysis instrument analyzes and calculates the mechanical properties of marine super-soft soil according to the data collected during the penetration of the spherical probe.

[0014] Preferably, the base is fixed by a positioning reaction force ground anchor, and the static penetration assembly is also provided with a centering guide for controlling the verticality of the hollow probe rod.

[0015] Preferably, the centering guide is sleeved on the outer circumference of the hollow probe rod, and the hollow probe rod is made of stainless steel.

[0016] Preferably, the side expansion membranes are located on both sides of the equator of the spherical probe and are symmetrical about the equator.

[0017] Preferably, a top column which can be connected to the hollow probe rod is arranged on the top of the spherical probe, and the pore water pressure sensor is arranged on the periphery of the top column.

[0018] Preferably, the data acquisition and analysis instrument calculates the marine supersoft soil sensitivity S according to the following formula: t :

[0019]

[0020] Where N s is the sensitivity correction coefficient, the value range is: 0.15~2.50; q t To correct the ball head resistance; f s is the side wall friction force detected by the side wall friction force sensor; σ v0 is the overlying soil pressure;

[0021] Corrected ball head resistance q t The calculation formula is:

[0022]

[0023] Where a is the effective area ratio, which is defined as the ratio of the cross-sectional area of ​​the top column at the pore water pressure sensor to the cross-sectional area of ​​the ball head base; A s and A p are the projection areas of the hollow probe rod and the spherical probe, respectively, q m is the penetration resistance detected by the spherical resistance sensor, and u0 is the pore water pressure measured by the pore water pressure sensor.

[0024] Optimally, the overburden pressure σ v0 The calculation formula is:

[0025] σ v0 =∑γ i ·h i

[0026] In the formula, γ i is the density of the overlying i-th layer of soil; h i is the thickness of the overlying soil layer i; q m When the value change is less than 10kPa, it is the same layer of soil.

[0027] Preferably, the data acquisition and analysis instrument calculates the undrained shear strength c of marine supersoft soil according to the following formula: u :

[0028]

[0029] In the formula, χ is a dimensionless constant, ranging from 12 to 13.2; E is the correction factor of lateral expansion modulus; Dis the lateral expansion modulus;

[0030] Lateral expansion modulus E D The calculation formula is:

[0031]

[0032] Where A0 and B0 are the initial dive of the spherical probe into the ultra-soft soil in the ocean, q m When the pressure is 2kPa, stop diving, adjust all readings of the data acquisition analyzer to zero, turn on the air pressure source, and apply air pressure to the side expansion diaphragm through the air pressure pipeline. The air pressure value when the side expansion diaphragm deformation reaches 0.05mm and 1.10mm;

[0033] A z , B z They are the air pressure values ​​when the spherical probe stops diving for the zth time according to the set rules during the penetration process, the air pressure source is turned on, and the air pressure is applied to the side expansion diaphragm through the air pressure pipeline, and the deformation of the side expansion diaphragm reaches 0.05mm and 1.10mm.

[0034] An in-situ testing method for marine supersoft soil, using any of the in-situ testing devices described above, comprises the following steps:

[0035] Step 1: When ready, adjust the centering guide to keep the hollow probe vertical, and adjust the position of the spherical probe to the designated test point;

[0036] Step 2: gradually lower the spherical probe from above the sea surface to the surface of the ultra-soft soil. When the penetration resistance q of the spherical resistance sensor is m When the reading is equal to 2kPa, the penetration rate control box controls the spherical probe to stop diving; adjust the readings of the data acquisition analyzer to zero, turn on the air pressure source, apply gas pressure to the side expansion diaphragm through the air pressure pipeline, and record the air pressure values ​​when the side expansion diaphragm deformation reaches 0.05mm and 1.10mm, which are recorded as A0 and B0 respectively; turn off the air pressure source, open the exhaust valve, and restore the side expansion diaphragm to the initial state of zero air pressure;

[0037] Step 3: Set the penetration rate to 2 mm / s through the penetration rate control box. During the penetration of the spherical probe, the data acquisition analyzer records the pore water pressure u0 and the penetration resistance q every 2 mm. m and side wall friction f s After each penetration of 200 mm, pause once, open the air pressure source to apply air pressure to the side expansion diaphragm, and record the air pressure value when the side expansion diaphragm is deformed to 0.05 mm and 1.10 mm. In this step, the zth detection value is recorded as A z and B z ; Turn off the air pressure source, open the exhaust valve to release the air pressure, and after the side expansion diaphragm returns to the initial state of zero air pressure, continue to penetrate the spherical probe;

[0038] Step 4: Stop penetration when the spherical probe reaches the predetermined depth or two consecutive sets of data meet the following conditions:

[0039] 1.05(B z -A z )-2.05A0-0.05B0>20 or q m >50kPa

[0040] Step 5: The penetration rate control box controls the spherical probe to be pulled upward until the spherical probe leaves the marine super-soft soil.

[0041] Preferred:

[0042] The data acquisition and analysis instrument calculates the marine supersoft soil sensitivity S according to the following formula t :

[0043]

[0044] Among them, the corrected ball head resistance q t The calculation formula is:

[0045]

[0046] Where, the overburden pressure σ v0 The calculation formula is:

[0047] σ v0 =∑γ i ·h i

[0048] The data acquisition and analysis instrument calculates the undrained shear strength c of marine supersoft soil according to the following formula u :

[0049]

[0050] Among them, the lateral expansion modulus E D The calculation formula is:

[0051]

[0052] The beneficial effects of the present invention are:

[0053] 1. The spherical probe of the present invention can overcome the limitation of the small contact area between the traditional conical probe and the test soil, so that the fluid marine high-sensitivity ultra-soft soil fully surrounds the ball head, providing greater ball head resistance and side wall friction, and the large-diameter ball head can effectively capture the subtle changes in the ultra-soft soil resistance, thereby providing more accurate test data.

[0054] 2. The present invention uses a lateral expansion diaphragm with an extremely low elastic modulus to test the deformation modulus of soft soil. Under the conditions of applying a low pressure stress environment and rarely disturbing the soil, the stress-strain relationship of highly sensitive ultra-soft soil can be accurately tested in situ, avoiding the damage to the original state of the soil during the gas pressure process, and providing reliable guarantee for the collection of various data during the subsequent ball head penetration process. In addition, various soil property parameters such as stress, deformation and water pressure can be obtained during the penetration of the spherical probe and the deformation of the lateral expansion diaphragm, which has the advantage of mutual verification between different testing methods.

[0055] 3. The calculation of the lateral expansion modulus of the present invention takes into account the influence of pore water pressure and equipment geometric dimensions on the stress-strain characteristics of the lateral expansion diaphragm, which can effectively reduce the calculation error and obtain a more accurate and reliable deformation modulus value of marine supersoft soil.

[0056] 4. The present invention corrects the data processing when calculating the sensitivity and undrained shear strength of marine soft soil, wherein the overburden pressure is calculated by a linear function to obtain the development trend of the overburden pressure with the penetration depth, and the sensitivity correction coefficient is considered to eliminate the calculation error of the sensitivity due to the change of the penetration depth; when calculating the lateral expansion modulus, the calculation error of the lateral expansion modulus due to the change of sensitivity is eliminated. In addition, the present invention adopts the calculation method of ball head resistance and side wall resistance corrected by pore pressure, which eliminates the calculation error of the sensitivity and undrained shear strength due to the change of pore water pressure.

[0057] 5. Pore water pressure and overburden pressure are important indicators for evaluating the in-situ state of marine high sensitivity and ultra-soft soil, and cannot be ignored when measuring and calculating soil mechanical property parameters. When calculating the sensitivity of marine soft soil, the present invention corrects the ball head resistance by pore water pressure, water pressure sensor structure and probe geometric dimensions, not only considering the influence of pore water pressure on the ball head resistance during the penetration process, but also balancing the difference in the force of the upper and lower soil bodies during the probe penetration process caused by the small cross-sectional area of ​​the probe rod, while eliminating the dynamic error of the overburden pressure on the ball head resistance measurement; when calculating the undrained shear strength of marine soft soil, the power function and natural logarithm function are used to calculate the sensitivity, undrained shear strength and lateral expansion modulus, respectively, to establish the intrinsic connection between the three mechanical property indicators, while eliminating the calculation error of the overburden pressure and pore water pressure on the undrained shear strength of the in-situ soft soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a structural schematic diagram of an in-situ testing device for marine super-soft soil according to the present invention;

[0059] Figure 2 It is a structural schematic diagram of a spherical probe of the present invention;

[0060] The meanings of the symbols in the accompanying drawings are as follows:

[0061] 1. Spherical probe; 2. Lateral expansion diaphragm; 3. Ball-shaped resistance sensor; 4. Side wall friction resistance sensor; 5. Pore water pressure sensor; 6. Hollow probe rod; 7. Diaphragm signal data line; 8. Air pressure pipeline; 9. Probing signal data line; 10. Data acquisition and analysis instrument; 11. Exhaust valve; 12. Air pressure source; 13. Reaction anchor; 14. Fixing bolt; 15. Base; 16. Centering guide; 17. Penetration rate control box. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0063] like Figure 1 As shown, an in-situ testing device for marine super-soft soil includes two major parts: a spherical sounding component and a static penetration component, which are specifically introduced below.

[0064] The spherical probe assembly includes a data acquisition analyzer 10, an air pressure source 12, a connected spherical probe 1 and a hollow probe rod 6. Specifically, Figure 2 As shown, the spherical probe 1 is provided with a ball-head resistance sensor 3, a side wall friction resistance sensor 4, a side expansion membrane 2 and a pore water pressure sensor 5 in sequence from the bottom to the top. The ball-head resistance sensor 3 is located at the bottom center of the spherical probe 1 and is spaced a set distance from the side wall friction resistance sensor 4. The side wall friction resistance sensors 4 are arranged in a circle.

[0065] The side expansion membrane 2 is spaced a set distance from the side wall friction sensor 4. Preferably, the side expansion membrane 2 is located on both sides of the equator of the spherical probe 1 and is symmetrical about the equator. The top of the spherical probe 1 is provided with a top column that can be connected to the hollow probe rod 6. The pore water pressure sensor 5 is arranged on the periphery of the top column. During the penetration process, the pore water pressure sensor 5 contacts the marine super soft soil to detect its pore water pressure.

[0066] by Figure 2 The embodiment shown in is used as a reference: the spherical probe 1 is a hollow stainless steel sphere with a diameter of 150 mm, a wall thickness of 5 mm, and an elastic modulus of not less than 150 GPa; the side expansion diaphragm 2 is circular, located on both sides of the spherical probe 1 symmetrically at the equator, made of stainless steel, with a diameter of 60 mm and an elastic modulus of 100 kPa to 300 kPa; the center of the side wall friction sensor 4 is 25 mm away from the end point of the spherical probe 1 in a vertical distance; the pore water pressure sensor 5 is composed of a water permeable filter and a pressure sensor, and is 5 mm away from the top of the spherical probe 1.

[0067] The ball-shaped resistance sensor 3, the side wall friction resistance sensor 4 and the pore water pressure sensor 5 are connected to the data acquisition analyzer 10 through the sounding signal data line 9, and the side expansion diaphragm 2 is connected to the data acquisition analyzer 10 through the diaphragm signal data line 7 and the air pressure pipeline 8 respectively. The air pressure pipeline 8 is connected to the air pressure source 12 and the air pressure pipeline 8 is provided with an exhaust valve 11. The air pressure pipeline 8 is a line for conveying gas. The air pressure source 12 applies gas pressure to the side expansion diaphragm 2 through the air pressure pipeline 8, and the side expansion diaphragm 2 is restored to the initial state of zero air pressure through the exhaust valve 11. The air pressure source 12 can provide nitrogen with a pressure range of 10kPa-1000kPa. The opening and closing of the air pressure source 12 can be controlled by personnel, or by a controller. The exhaust valve 11 can be used to adjust the gas pressure applied to the side expansion diaphragm 2, and the data acquisition analyzer 10 can collect its air pressure value in real time.

[0068] The static penetration assembly includes a base 15 for supporting the spherical sounding assembly and a penetration rate control box 17 for controlling the movement of the spherical probe 1. The base 15 can be fixed by a positioning reaction anchor 13, and the positioning reaction anchor 13 is connected to the base 15 by a fixing bolt 14. The static penetration assembly is also provided with a centering guide 16 for controlling the verticality of the hollow probe rod 6.

[0069] by Figure 1 The embodiment shown in is used as a reference: the centering guide 16 is sleeved on the outer periphery of the hollow probe rod 6, wherein the hollow probe rod 6 is made of stainless steel; a circular hole with a diameter of 20 cm is provided at the center of the base 15, and a level bubble is installed on one side of the circular hole for adjusting the level; the centering guide 16 can adjust the verticality of the stainless steel hollow probe rod 6 through a scale knob; the penetration rate control box 17 controls the penetration (extraction) rate of the spherical probe 1 to maintain 0-60 (±0.1) mm / s. The spherical probe 1 is installed at the end of the stainless steel hollow probe rod 6, and the diaphragm signal data line 7, the air pressure pipeline 8 and the sounding signal data line 9 pass through the stainless steel hollow probe rod 6 and are connected to the data acquisition analyzer 10. At the same time, the stainless steel hollow probe rod 6 passes through the penetration rate control box 17 and the centering guide 16 in turn; the scale knob of the centering guide 16 is adjusted to ensure the verticality of the stainless steel hollow probe rod 6 and the position of the spherical probe 1.

[0070] The data acquisition and analysis instrument 10 analyzes and calculates the mechanical properties of marine super-soft soil according to the data collected during the penetration of the spherical probe 1, specifically:

[0071] The data acquisition and analysis instrument 10 calculates the marine supersoft soil sensitivity S according to the following formula t :

[0072]

[0073] Where N sis the sensitivity correction coefficient, the value range is: 0.15~2.50; q t To correct the ball head resistance; f s is the side wall friction force detected by the side wall friction force sensor 4; σ v0 is the overlying soil pressure;

[0074] Corrected ball head resistance q t The calculation formula is:

[0075]

[0076] Wherein, a is the effective area ratio, which is defined as the ratio of the cross-sectional area of ​​the top column at the pore water pressure sensor 5 to the cross-sectional area of ​​the ball head base 15, and in this embodiment, the value is 0.84; A s and A p are the projection areas of the hollow probe rod 6 and the spherical probe 1, respectively. In this embodiment, A s =10.0cm 2 , A p =176.7cm 2 ,q m is the penetration resistance detected by the spherical resistance sensor 3, and u0 is the pore water pressure measured by the pore water pressure sensor 5.

[0077] Overburden pressureσ v0 The calculation formula is:

[0078] σ v0 =∑γ i ·h i

[0079] In the formula, γ i is the density of the overlying i-th layer of soil; h i is the thickness of the overlying soil layer i; q detected during the penetration of the spherical probe 1 m When the value change is less than 10kpa, it is the same layer of soil, and each layer can be determined similarly.

[0080] The data acquisition and analysis instrument 10 calculates the undrained shear strength c of marine supersoft soil according to the following formula u :

[0081]

[0082] In the formula, χ is a dimensionless constant, ranging from 12 to 13.2; E is the lateral expansion modulus correction coefficient, which is 0.25 in this embodiment; D is the lateral expansion modulus;

[0083] Lateral expansion modulus E D The calculation formula is:

[0084]

[0085] Where A0 and B0 are the initial dive of the spherical probe 1 into the marine super-soft soil, q m When the pressure is 2 kPa, the dive is stopped, the readings of the data acquisition analyzer 10 are adjusted to zero, the air pressure source 12 is turned on, and the air pressure is applied to the side expansion diaphragm 2 through the air pressure pipeline 8, and the air pressure value when the side expansion diaphragm 2 is deformed to 0.05 mm and 1.10 mm;

[0086] A z , B z They are the air pressure values ​​when the spherical probe 1 stops diving for the zth time according to the set rules during the penetration process, the air pressure source 12 is turned on, and the air pressure is applied to the side expansion diaphragm 2 through the air pressure pipeline 8, and the deformation of the side expansion diaphragm 2 reaches 0.05mm and 1.10mm.

[0087] Correspondingly, an in-situ testing method for marine supersoft soil, using any of the in-situ testing devices described above, comprises the following steps:

[0088] Step 1: After preparation, adjust the centering guide 16 to maintain the verticality of the hollow probe rod 6, and adjust the position of the spherical probe 1 to the designated test point;

[0089] Step 2: Use relevant equipment to gradually lower the spherical probe 1 from above the sea surface to the surface of the super-soft soil. When the penetration resistance q of the spherical resistance sensor 3 is m When the reading is equal to 2 kPa, the penetration rate control box 17 controls the spherical probe 1 to stop diving; adjust the readings of the data acquisition analyzer 10 to zero, turn on the air pressure source 12, slowly apply gas pressure to the side expansion diaphragm 2 through the air pressure pipeline 8, and record the air pressure values ​​when the deformation of the side expansion diaphragm 2 reaches 0.05 mm and 1.10 mm, which are recorded as A0 and B0 (unit: kPa) respectively; turn off the air pressure source 12, slowly open the exhaust valve 11, and restore the side expansion diaphragm 2 to the initial state of zero air pressure;

[0090] Step 3: Set the penetration rate to 2 mm / s through the penetration rate control box 17. During the penetration of the spherical probe 1, the data acquisition analyzer 10 records the pore water pressure u0 and the penetration resistance q every 2 mm. m and side wall friction f s (Unit: kPa); Pause once after each penetration of 200 mm, open the air pressure source 12 and slowly apply air pressure to the side expansion diaphragm 2, and record the air pressure value when the side expansion diaphragm 2 is deformed to 0.05 mm and 1.10 mm. In this step, the detection value of the zth time is recorded as A z and (unit: kPa)B z; Turn off the air pressure source 12, slowly open the exhaust valve 11 to release the air pressure, and after the side expansion diaphragm 2 returns to the initial state of zero pressure, continue to penetrate the spherical probe 1;

[0091] Step 4: Stop penetration when the spherical probe 1 reaches the predetermined depth or two consecutive sets of data meet the following conditions:

[0092] 1.05(B z -A z )-2.05A0-0.05B0>20 or q m >50kPa

[0093] Step 5: The penetration rate control box 17 controls the spherical probe 1 to be pulled upward until the spherical probe 1 leaves the marine super-soft soil. The upward pulling rate can be set to 2 mm / s.

[0094] The data acquisition and analysis instrument 10 calculates the marine supersoft soil sensitivity S according to the following formula: t :

[0095]

[0096] Among them, the corrected ball head resistance q t The calculation formula is:

[0097]

[0098] Where, the overburden pressure σ v0 The calculation formula is:

[0099] σ v0 =∑γ i ·h i

[0100] The data acquisition and analysis instrument 10 calculates the undrained shear strength c of marine supersoft soil according to the following formula u :

[0101]

[0102] Among them, the lateral expansion modulus E D The calculation formula is:

[0103]

[0104] 1. The spherical probe of the present invention can overcome the limitation of the small contact area between the traditional conical probe and the test soil, so that the fluid marine high-sensitivity ultra-soft soil fully surrounds the ball head, providing greater ball head resistance and side wall friction, and the large-diameter ball head can effectively capture the subtle changes in the ultra-soft soil resistance, thereby providing more accurate test data.

[0105] 2. The present invention uses a lateral expansion diaphragm with an extremely low elastic modulus to test the deformation modulus of soft soil. Under the conditions of applying a low pressure stress environment and rarely disturbing the soil, the stress-strain relationship of highly sensitive ultra-soft soil can be accurately tested in situ, avoiding the damage to the original state of the soil during the gas pressure process, and providing reliable guarantee for the collection of various data during the subsequent ball head penetration process. In addition, various soil property parameters such as stress, deformation and water pressure can be obtained during the penetration of the spherical probe and the deformation of the lateral expansion diaphragm, which has the advantage of mutual verification between different testing methods.

[0106] 3. The calculation of the lateral expansion modulus of the present invention takes into account the influence of pore water pressure and equipment geometric dimensions on the stress-strain characteristics of the lateral expansion diaphragm, which can effectively reduce the calculation error and obtain a more accurate and reliable deformation modulus value of marine supersoft soil.

[0107] 4. The present invention corrects the data processing when calculating the sensitivity and undrained shear strength of marine soft soil, wherein the overburden pressure is calculated by a linear function to obtain the development trend of the overburden pressure with the penetration depth, and the sensitivity correction coefficient is considered to eliminate the calculation error of the sensitivity due to the change of the penetration depth; when calculating the lateral expansion modulus, the calculation error of the lateral expansion modulus due to the change of sensitivity is eliminated. In addition, the present invention adopts the calculation method of ball head resistance and side wall resistance corrected by pore pressure, which eliminates the calculation error of the sensitivity and undrained shear strength due to the change of pore water pressure.

[0108] 5. Pore water pressure and overburden pressure are important indicators for evaluating the in-situ state of marine high sensitivity and ultra-soft soil, and cannot be ignored when measuring and calculating soil mechanical property parameters. When calculating the sensitivity of marine soft soil, the present invention corrects the ball head resistance by pore water pressure, water pressure sensor structure and probe geometric dimensions, not only considering the influence of pore water pressure on the ball head resistance during the penetration process, but also balancing the difference in the force of the upper and lower soil bodies during the probe penetration process caused by the small cross-sectional area of ​​the probe rod, while eliminating the dynamic error of the overburden pressure on the ball head resistance measurement; when calculating the undrained shear strength of marine soft soil, the power function and natural logarithm function are used to calculate the sensitivity, undrained shear strength and lateral expansion modulus, respectively, to establish the intrinsic connection between the three mechanical property indicators, while eliminating the calculation error of the overburden pressure and pore water pressure on the undrained shear strength of the in-situ soft soil.

[0109] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An in-situ testing device for marine super-soft soil, comprising a spherical sounding assembly and a static penetration assembly, characterized in that: The spherical sounding assembly comprises a data acquisition analyzer (10), an air pressure source (12), a connected spherical probe (1) and a hollow probe rod (6); the spherical probe (1) is provided with a ball-shaped resistance sensor (3), a side wall friction resistance sensor (4), a side expansion membrane (2) and a pore water pressure sensor (5) in sequence from the bottom to the top; the ball-shaped resistance sensor (3), the side wall friction resistance sensor (4) and the pore water pressure sensor (5) are connected to the data acquisition analyzer (10) via a sounding signal data line (9); the side expansion membrane (2) is connected to the data acquisition analyzer (10) via a membrane signal data line (7) and an air pressure pipeline (8); the air pressure pipeline (8) is connected to the air pressure source (12) and the air pressure pipeline (8) is provided with an exhaust valve (11); the air pressure source (12) applies air pressure to the side expansion membrane (2) via the air pressure pipeline (8); The static penetration assembly comprises a base (15) for supporting the spherical sounding assembly and a penetration rate control box (17) for controlling the movement of the spherical probe (1); The data acquisition and analysis instrument (10) analyzes and calculates the mechanical properties of marine super-soft soil based on the data collected during the penetration of the spherical probe (1).

2. The in-situ testing device for marine supersoft soil according to claim 1, characterized in that: The base (15) is fixed by a positioning reaction force anchor (13), and the static penetration assembly is also provided with a centering guide (16) for controlling the verticality of the hollow probe rod (6).

3. The in-situ testing device for marine supersoft soil according to claim 2, characterized in that: The centering guide (16) is sleeved on the outer circumference of the hollow probe rod (6), and the hollow probe rod (6) is made of stainless steel.

4. The in-situ testing device for marine supersoft soil according to claim 1, characterized in that: The side expansion membranes (2) are located on both sides of the equator of the spherical probe (1) and are symmetrical about the equator.

5. The in-situ testing device for marine supersoft soil according to claim 4, characterized in that: A top column which can be connected to a hollow probe rod (6) is arranged at the top of the spherical probe (1), and the pore water pressure sensor (5) is arranged on the periphery of the top column.

6. The in-situ testing device for marine supersoft soil according to claim 1, characterized in that: The data acquisition and analysis instrument (10) calculates the marine super-soft soil sensitivity S according to the following formula: t : Where N s is the sensitivity correction coefficient, the value range is: 0.15~2.50; q t To correct the ball head resistance; f s is the side wall friction force detected by the side wall friction force sensor (4); σ v0 is the overlying soil pressure; Corrected ball head resistance q t The calculation formula is: Where a is the effective area ratio, which is defined as the ratio of the cross-sectional area of ​​the top column at the pore water pressure sensor (5) to the cross-sectional area of ​​the ball head base (15); A s and A p are the projected areas of the hollow probe rod (6) and the spherical probe (1), respectively, and q m is the penetration resistance detected by the ball-shaped resistance sensor (3), and u0 is the pore water pressure measured by the pore water pressure sensor (5).

7. The in-situ testing device for marine supersoft soil according to claim 6, characterized in that: Overburden pressureσ v0 The calculation formula is: s v0 =∑γ i ·h i In the formula, γ i is the density of the overlying i-th layer of soil; h i is the thickness of the overlying soil layer i; q detected during the penetration of the spherical probe (1) m When the value change is less than 10kPa, it is the same layer of soil.

8. The in-situ testing device for marine supersoft soil according to claim 6, characterized in that: The data acquisition and analysis instrument (10) calculates the undrained shear strength c of marine supersoft soil according to the following formula: u : In the formula, χ is a dimensionless constant, ranging from 12 to 13.2; E is the correction factor of lateral expansion modulus; D is the lateral expansion modulus; Lateral expansion modulus E D The calculation formula is: Where A0 and B0 are the initial dive of the spherical probe (1) into the marine super-soft soil, q m When the pressure reaches 2 kPa, the dive is stopped, the readings of the data acquisition analyzer (10) are adjusted to zero, the air pressure source (12) is turned on, and air pressure is applied to the side expansion diaphragm (2) through the air pressure pipeline (8), and the air pressure value when the side expansion diaphragm (2) is deformed to 0.05 mm and 1.10 mm; A z , B z The spherical probe (1) stops diving for the zth time according to the set rules during the penetration process, opens the air pressure source (12), applies air pressure to the side expansion diaphragm (2) through the air pressure pipeline (8), and the air pressure values ​​when the deformation of the side expansion diaphragm (2) reaches 0.05 mm and 1.10 mm.

9. An in-situ testing method for marine supersoft soil, using the in-situ testing device according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: After preparation, adjust the centering guide (16) to maintain the verticality of the hollow probe rod (6), and adjust the position of the spherical probe (1) to correspond to the designated test point; Step 2: gradually lower the spherical probe (1) from above the sea surface to the surface of the ultra-soft soil. When the penetration resistance q of the spherical resistance sensor (3) m When the reading is equal to 2 kPa, the penetration rate control box (17) controls the spherical probe (1) to stop diving; adjust the readings of the data acquisition analyzer (10) to zero, turn on the air pressure source (12), apply air pressure to the side expansion diaphragm (2) through the air pressure pipeline (8), and record the air pressure values ​​when the side expansion diaphragm (2) deforms to 0.05 mm and 1.10 mm, which are recorded as A0 and B0 respectively; turn off the air pressure source (12), open the exhaust valve (11), and restore the side expansion diaphragm (2) to the initial state of zero air pressure; Step 3: Set the penetration rate to 2 mm / s through the penetration rate control box (17). During the penetration of the spherical probe (1), the data acquisition analyzer (10) records the pore water pressure u0 and the penetration resistance q every 2 mm. m and side wall friction f s After each penetration of 200 mm, pause once, open the air pressure source (12) to apply air pressure to the lateral expansion membrane (2), and record the air pressure value when the lateral expansion membrane (2) is deformed to 0.05 mm and 1.10 mm. In this step, the detection value of the zth time is recorded as A z and B z ; Turn off the air pressure source (12), open the exhaust valve (11) to release the air pressure, and after the side expansion diaphragm (2) returns to the initial state of zero air pressure, continue to penetrate the spherical probe (1); Step 4: When the spherical probe (1) reaches the predetermined depth or two consecutive sets of data meet the following conditions, the penetration is stopped: 1.05(B z -A z 0-2.05A0-0.05B0>20 or q m >50kPa Step 5: The penetration rate control box (17) controls the spherical probe (1) to be pulled upward until the spherical probe (1) leaves the marine super-soft soil.

10. The in-situ testing method of marine supersoft soil according to claim 9, characterized in that: The data acquisition and analysis instrument (10) calculates the marine super-soft soil sensitivity S according to the following formula: t : Among them, the corrected ball head resistance q t The calculation formula is: Where, the overburden pressure σ v0 The calculation formula is: s v0 =∑γ i ·h i The data acquisition and analysis instrument (10) calculates the undrained shear strength c of marine supersoft soil according to the following formula: u : Among them, the lateral expansion modulus E D The calculation formula is:

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