A method for interpreting deep-sea soil parameters

Abstract

The present invention relates to the technical field of deep-sea soil exploration, and more particularly to a method for interpreting deep-sea soil parameters. The method comprises: reshaping the deep-sea soil and preparing mud, pouring the mud into a large calibration tank and consolidating it with in-situ stress; conducting a static penetration model test on the consolidated mud to obtain cone tip resistance and pore water pressure; pouring the mud into a large-diameter oedometer and consolidating it with in-situ stress; pushing the soil sample in the large-diameter oedometer to prepare a triaxial specimen, and performing k0 consolidation in a bending element triaxial instrument with the in-situ stress to obtain a standard soil sample; conducting an undrained shear test on the standard soil sample to obtain the undrained shear strength of the standard soil sample, and interpreting the deep-sea soil parameters by comprehensively considering the cone tip resistance and pore water pressure. The present invention improves the accuracy of deep-sea soil parameter interpretation.

Description

Technical Field

[0001] The present invention relates to the technical field of deep-sea soil exploration, and in particular to a method for interpreting deep-sea soil parameters. Background Art

[0002] my country's marine development is currently shifting from traditional engineering projects to new ones, with the scale of projects increasing and the trend shifting from nearshore and shallow waters to offshore and deep waters. Marine engineering surveys are a core component of marine engineering construction, crucially impacting the safety and durability of marine projects.

[0003] During marine engineering surveys, both domestically and internationally, static penetration testing is the primary method, with drilling sampling and laboratory geotechnical testing serving as verification methods. However, static penetration testing cannot directly reveal soil parameters, requiring calibration using other in-situ testing methods (such as in-situ cross-plate shear tests) or laboratory testing on undisturbed or slightly disturbed specimens (such as direct shear tests and triaxial tests). Conventional drilling sampling significantly disturbs the soil, as cross-plate insertion is difficult to maintain verticality and uneven soil stress can lead to measurement errors. Furthermore, in-situ soil layers are often heterogeneous, resulting in significant variations in soil properties at different locations. Direct comparisons to calibrate soil parameters can therefore result in significant errors. Therefore, using laboratory model tests to control soil uniformity and simulate soil samples at different depths by controlling consolidation stresses is the most direct, simple, and effective method for calibrating soil parameters. The existing static penetration interpretation parameter calibration method using indoor model tests has low parameter accuracy due to the large disturbance to the soil during the subsequent sampling process, which is quite different from the properties of the simulated in-situ soil samples. Summary of the Invention

[0004] In order to solve the problem of low accuracy in interpreting deep-sea soil parameters in existing methods, the present invention aims to provide a method for interpreting deep-sea soil parameters. The technical solution adopted is as follows:

[0005] The present invention provides a method for interpreting deep-sea soil parameters, which includes the following steps:

[0006] Reshape deep-sea soil and prepare mud;

[0007] Pour the slurry into a large calibration tank for consolidation using in-situ stress;

[0008] Conduct a static penetration test on the cemented slurry to obtain the cone tip resistance and pore water pressure;

[0009] pouring the slurry into a large diameter oedometer for consolidation using the in-situ stress;

[0010] The soil sample in the large-diameter oedometer is pushed out to prepare a triaxial specimen, and k0 consolidation is performed in a bending element triaxial apparatus with the in-situ stress to obtain a standard soil sample; an undrained shear test is performed on the standard soil sample to obtain the undrained shear strength of the standard soil sample;

[0011] The undrained shear strength, cone tip resistance and pore water pressure are comprehensively considered to interpret the deep-sea soil parameters.

[0012] Preferably, the reshaping of the deep-sea soil and preparation of mud comprises:

[0013] Mixing deep-sea soil particles with a salt solution of a preset concentration at a preset pH value to obtain a slurry;

[0014] The preset salt solution concentration is 3.5% to 3.7%, and the preset pH value is 7.5 to 8.2.

[0015] Preferably, before pouring the mud into a large calibration tank for consolidation with in-situ stress, the method further includes: using the pore water pressure corresponding to the water depth of the in-situ soil as counter pressure, and applying water pressure to the soil to simulate the high water pressure environment of the deep-sea soil.

[0016] Preferably, the static penetration model test is performed on the mud after consolidation to obtain the cone tip resistance and pore water pressure, including: performing a static penetration test at the center of the calibration tank, installing the static penetration probe to the static penetration rod, using a penetration device to penetrate the static penetration rod into the soil at a uniform speed of 20 mm / s, and recording the cone tip resistance and pore water pressure.

[0017] Preferably, the acquisition of the standard soil sample includes: if the numerical error between the shear wave velocity of the soil sample after consolidation in the bending element triaxial instrument and the shear wave velocity of the soil after consolidation in the large calibration tank model test is within a preset error, then the soil sample after consolidation in the bending element triaxial instrument is used as the standard soil sample.

[0018] Preferably, the interpreting of deep-sea soil parameters includes:

[0019] The interpretation formula of undrained shear strength of clay by static cone penetration test is:

[0020] ;

[0021] The formula for interpreting the parameters is:

[0022] ;

[0023] ;

[0024] in, is the undrained shear strength of clay, is the undrained shear strength of the standard soil sample, To interpret the parameters, is the soil self-weight stress at the static penetration location, To correct the cone tip resistance, is the cone tip resistance, is the pore water pressure, is the effective area ratio.

[0025] The present invention has at least the following beneficial effects:

[0026] In the process of interpreting deep-sea soil parameters, the present invention first reshapes the deep-sea soil and prepares mud; pours the mud into a large calibration tank and consolidates it with in-situ stress; then performs a static penetration model test on the consolidated mud to obtain cone tip resistance and pore water pressure; and pours the mud into a large-diameter oedometer and consolidates it with in-situ stress. The soil sample in the large-diameter oedometer is pushed out to prepare a triaxial specimen, and k0 consolidation is performed with in-situ stress in a bending element triaxial instrument to prepare a standard soil sample, thereby avoiding disturbance of the soil sample during the sampling process and restoring the initial stress state. The method provided in this embodiment fully considers the hydrochemistry and water depth environment of the soil in situ, better restores the soil state, improves the accuracy of soil parameter interpretation, reduces engineering construction costs, and has important theoretical and practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A flow chart of a method for interpreting deep-sea soil parameters provided by an embodiment of the present invention;

[0029] Figure 2 This is a mechanical structure diagram of a large calibration tank according to an embodiment of the present invention;

[0030] Figure 3 FIG1 is a mechanical structure diagram of a large diameter consolidation instrument according to an embodiment of the present invention;

[0031] Figure 4 FIG1 is a mechanical structure diagram of a static penetration tester according to an embodiment of the present invention;

[0032] In the figure, 1 is a large calibration tank, 2 is a static penetration instrument, 3 is soil, 4 is the first pore pressure sensor, 5 is the first permeable stone, 6 is the base of the model tank, 7 is the consolidation cylinder, 8 is the water-stop rubber ring, 9 is the first consolidation cover, 10 is the reaction frame, 11 is the penetration system, 12 is the pressure volume controller, 13 is the data acquisition system, 14 is the micrometer, 15 is the pressure transmission screw, 16 is the second consolidation cover, 17 is the second permeable stone, 18 is distilled water, 19 is the third permeable stone, 20 is the balance hammer, 21 is the laboratory table, 22 is the lever, 23 is the hanging plate, 24 is soil, 25 is the static penetration rod, 26 is the second pore pressure sensor, and 27 is the cone tip resistance sensor. DETAILED DESCRIPTION

[0033] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a deep-sea soil parameter interpretation method proposed in accordance with the present invention is described in detail below with reference to the accompanying drawings and preferred embodiments.

[0034] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0035] The following describes in detail a method for interpreting deep-sea soil parameters provided by the present invention with reference to the accompanying drawings.

[0036] An embodiment of a method for interpreting deep-sea soil parameters:

[0037] In this embodiment, deep-sea soil is reshaped and slurry is prepared. The slurry is poured into a large calibration tank for consolidation with in-situ stress. After consolidation is completed, a static penetration model test is performed. At the same time, the same slurry is poured into a large-diameter oedometer for consolidation with the same in-situ stress. The soil sample in the large-diameter oedometer is pushed out to prepare a triaxial sample. K0 consolidation is performed in the triaxial instrument with the same in-situ stress. The soil sample in this state is used as a standard soil sample for an undrained shear test to obtain the undrained shear strength of the standard sample. The strength parameters of the standard sample are linked to the static penetration soil interpretation parameters, thereby achieving the purpose of accurately interpreting the deep-sea soil parameters.

[0038] This embodiment proposes a method for interpreting deep-sea soil parameters, such as Figure 1 As shown, a deep-sea soil parameter interpretation method of this embodiment includes the following steps:

[0039] Step S1: reshape the deep-sea soil and prepare mud.

[0040] In this example, deep-sea soil is first prepared as a slurry. The soil is air-dried or oven-dried below 60°C, then carefully ground and passed through a 2mm sieve. Based on the deep-sea soil and water chemistry, the slurry is then mixed with a salt solution of a predetermined concentration and pH, which is then poured into a slurry mixing system and thoroughly stirred to produce a 2x liquid limit slurry sample. In this example, the predetermined concentration is 3.5% to 3.7%, and the predetermined pH is 7.5 to 8.2.

[0041] Step S2: pouring the slurry into a large calibration tank and consolidating it using in-situ stress.

[0042] Pour the mud into the calibration tank of the large calibration tank, and use the pressure volume controller 12 to apply a back pressure corresponding to a certain water depth to the mud to simulate the marine water pressure environment under the actual stratum. Use the consolidation cylinder (including displacement sensor) 7 to pressurize with a certain consolidation pressure (corresponding to the effective stress at different depths of the soil, set to 100kPa, 200kPa, 300kPa), and use the pore pressure sensor 4 to monitor the changes in the excess pore water pressure under the soil sample in real time. When the consolidation degree of the soil sample reaches 95%, the consolidation is completed. Among them, the large calibration tank is as follows Figure 2 As shown in the figure, 1 is a large calibration tank, 2 is a static penetration instrument, 3 is soil, 4 is the first pore pressure sensor, 5 is the first permeable stone, 6 is the model tank base, 7 is the consolidation cylinder, 8 is the water-stop rubber ring, 9 is the first consolidation cover, 10 is the reaction frame, 11 is the penetration system, 12 is the pressure volume controller, and 13 is the data acquisition system.

[0043] Step S3: Conduct a static penetration test on the solidified mud to obtain the cone tip resistance and pore water pressure.

[0044] A static penetration test is carried out at the center of the calibration tank. The static penetration probe is installed on the probe rod. The static penetration rod 25 is penetrated into the soil at a constant speed of 20 mm / s using a static penetration instrument. The cone tip resistance and pore water pressure are recorded. Figure 4 As shown in the figure, 25 is a static penetration rod, 26 is a second pore pressure sensor, and 27 is a cone tip resistance sensor.

[0045] Step S4: pouring the slurry into a large diameter oedometer for consolidation using the in-situ stress.

[0046] Next, this embodiment will use a large diameter consolidator to consolidate the mud prepared in step S1. Figure 3 As shown in the figure, 14 is a micrometer, 15 is a pressure transmission screw, 16 is a second consolidation cover, 17 is a second permeable stone, 18 is distilled water, 19 is a third permeable stone, 20 is a balance hammer, 21 is a laboratory table, 22 is a lever, 23 is a hanging plate, and 24 is soil.

[0047] Specifically, the slurry prepared in step S1 is poured into a large-diameter oedometer, and the same consolidation pressure as that on the soil in the model trough is applied to the soil. When the consolidation degree of the soil sample reaches 95%, the consolidation is completed.

[0048] Step S5: Push the soil sample in the large-diameter oedometer out to prepare a triaxial specimen, perform k0 consolidation with the in-situ stress in a bending element triaxial apparatus to obtain a standard soil sample; perform an undrained shear test on the standard soil sample to obtain the undrained shear strength of the standard soil sample.

[0049] The consolidated soil sample from step S4 is pushed out at a constant speed of 10 mm / s. A standard-sized soil sample (39.1 mm in diameter and 80 mm in length) is cut using a triaxial soil sample cutter, minimizing disturbance to the soil sample. The soil sample is placed in a bending element triaxial apparatus. The same stress as the model tank soil sample is applied to the soil. The shear wave velocity of the bending element is recorded and compared with the shear wave velocity of the bending element. If the degree of agreement is high, it indicates minimal soil disturbance and the soil sample can be used as a standard sample for comparison. Specifically, if the numerical error between the shear wave velocity of the consolidated soil sample in the bending element triaxial apparatus and the shear wave velocity of the consolidated soil in the large calibration tank model test is within a preset error, the consolidated soil sample in the bending element triaxial apparatus is used as the standard soil sample. In this embodiment, the preset error is 5%. In specific applications, the implementer can set this error based on specific circumstances.

[0050] Furthermore, an undrained shear test is performed on the standard soil sample to obtain the undrained shear strength of the standard soil sample.

[0051] Step S6: interpreting the deep-sea soil parameters by comprehensively considering the undrained shear strength, cone tip resistance and pore water pressure.

[0052] Next, this embodiment will interpret the deep-sea soil parameters based on the undrained shear strength of the standard soil sample, the obtained cone tip resistance and pore water pressure.

[0053] The interpretation formula of undrained shear strength of clay by static cone penetration test is:

[0054] ;

[0055] when and The difference between the values ​​of is no more than 5%, and the undrained shear strength of the standard soil sample can be used as the undrained shear strength of the calibration tank soil sample; is the shear wave velocity of the bending element, is the shear wave velocity of the soil bending element.

[0056] The formula for interpreting the parameters is:

[0057] ;

[0058] ;

[0059] in, is the undrained shear strength of clay, is the undrained shear strength of the standard soil sample, To interpret the parameters, is the soil self-weight stress at the static penetration location, To correct the cone tip resistance, is the cone tip resistance, is the pore water pressure, It is the effective area ratio. Most probes are between 0.5 and 0.9, usually 0.75 or 0.8. In specific applications, the implementer determines it according to the specific situation.

[0060] At this point, the method provided in this embodiment has been used to complete the interpretation of deep-sea soil parameters.

[0061] In the process of interpreting deep-sea soil parameters, the present embodiment first reshapes the deep-sea soil and prepares mud; pours the mud into a large calibration tank and consolidates it with in-situ stress; then performs a static penetration model test on the consolidated mud to obtain the cone tip resistance and pore water pressure; and pours the mud into a large-diameter oedometer and consolidates it with in-situ stress. The soil sample in the large-diameter oedometer is pushed out to prepare a triaxial specimen, and k0 consolidation is performed with in-situ stress in a bending element triaxial instrument to prepare a standard soil sample, thereby avoiding disturbance of the soil sample during the sampling process and restoring the initial stress state. The method provided in the present embodiment fully considers the hydrochemistry and water depth environment of the soil in situ, better restores the soil state, improves the accuracy of soil parameter interpretation, and reduces engineering construction costs, which has important theoretical and practical significance.

[0062] It should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for interpreting deep-sea soil parameters, characterized in that: The method comprises the following steps: Reshape deep-sea soil and prepare mud; Pour the slurry into a large calibration tank for consolidation using in-situ stress; Conduct a static penetration test on the cemented slurry to obtain the cone tip resistance and pore water pressure; pouring the slurry into a large diameter oedometer for consolidation using the in-situ stress; The soil sample in the large-diameter oedometer is pushed out to prepare a triaxial specimen, and k0 consolidation is performed in a bending element triaxial apparatus with the in-situ stress to obtain a standard soil sample; an undrained shear test is performed on the standard soil sample to obtain the undrained shear strength of the standard soil sample; The undrained shear strength, cone tip resistance and pore water pressure are comprehensively considered to interpret the deep-sea soil parameters.

2. A method for interpreting deep-sea soil parameters according to claim 1, characterized in that: The reshaping of the deep-sea soil and preparation of mud comprises: Mixing deep-sea soil particles with a salt solution of a preset concentration at a preset pH value to obtain a slurry; The preset salt solution concentration is 3.5% to 3.7%, and the preset pH value is 7.5 to 8.

2.

3. The method for interpreting deep-sea soil parameters according to claim 1, characterized in that: Before pouring the mud into a large calibration tank for consolidation with in-situ stress, the method also includes: using the pore water pressure corresponding to the water depth of the in-situ soil as counter pressure, applying water pressure to the soil to simulate the high water pressure environment of the deep-sea soil.

4. A method for interpreting deep-sea soil parameters according to claim 1, characterized in that: The static penetration model test is performed on the mud after consolidation to obtain the cone tip resistance and pore water pressure, including: performing a static penetration test at the center of the calibration tank, installing the static penetration probe to the static penetration rod, using a penetration device to penetrate the static penetration rod into the soil at a uniform speed of 20 mm / s, and recording the cone tip resistance and pore water pressure.

5. The method for interpreting deep-sea soil parameters according to claim 1, characterized in that: The acquisition of the standard soil sample includes: if the numerical error between the shear wave velocity of the soil sample after consolidation in the bending element triaxial instrument and the shear wave velocity of the soil body after consolidation in the large calibration tank model test is within a preset error, then the soil sample after consolidation in the bending element triaxial instrument is used as the standard soil sample.

6. A method for interpreting deep-sea soil parameters according to claim 1, characterized in that: The interpretation of deep-sea soil parameters includes: The interpretation formula of undrained shear strength of clay by static cone penetration test is: ； The formula for interpreting the parameters is: ； ； in, is the undrained shear strength of clay, is the undrained shear strength of the standard soil sample, To interpret the parameters, is the soil self-weight stress at the static penetration location, To correct the cone tip resistance, is the cone tip resistance, is the pore water pressure, is the effective area ratio.

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