CN116950030A - Soft soil effective stress friction angle measurement method based on pore-pressure static cone penetration test - Google Patents

Soft soil effective stress friction angle measurement method based on pore-pressure static cone penetration test Download PDF

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CN116950030A
CN116950030A CN202310951544.5A CN202310951544A CN116950030A CN 116950030 A CN116950030 A CN 116950030A CN 202310951544 A CN202310951544 A CN 202310951544A CN 116950030 A CN116950030 A CN 116950030A
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effective stress
friction angle
penetration test
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欧阳仲坤
李昊羲
刘语诺
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Shenzhen International Graduate School of Tsinghua University
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Abstract

A soft soil effective stress friction angle measuring method based on a pore-pressure static cone penetration test comprises the following steps: carrying out a CPTu penetration test on a measured in-situ soil body by a pore-pressure static cone penetration test, and collecting cone tip resistance q of a cone probe along with depth change through a sensor t Side friction force f s And pore water pressure u 2 The method comprises the steps of carrying out a first treatment on the surface of the According to the collected cone tip resistance q t Side friction force f s And pore water pressure u 2 And (5) interpreting the effective stress friction angle of the measured in-situ soil body. Compared with the indoor high-grade geotechnical test, the method has low cost, convenience and rapidnessThe application is particularly useful for surveying large geotechnical projects or for handling soil conditions of high variability. The application can be applied to mature static cone penetration test equipment, has short calculation time, effectively saves cost, fills the blank of static cone penetration test in the aspect of measuring the effective stress intensity of the super-consolidated clay, and has wide application prospect in the aspects of soil intensity measurement and the like.

Description

Soft soil effective stress friction angle measurement method based on pore-pressure static cone penetration test
Technical Field
The application relates to marine geotechnical engineering geological survey, in particular to a soft soil effective stress friction angle measuring method based on a pore-pressure static cone penetration test.
Background
Marine geotechnical engineering geological survey requires acquisition of objective engineering characteristics of soil mass of implementation points of a construction project to accurately and properly perform construction project design and implementation. Both the hydrostatic cone penetration test (CPTu) and the advanced geotechnical test are methods of testing soil bodies and can be used for effectively deducing soil strata and interpreting geological parameters. Because the release of high confining pressure, the transportation of the soil sample and the manufacture of the test sample in the advanced geotechnical test process of the soil body can cause unavoidable disturbance to the soil sample, the result of the advanced geotechnical test may not completely represent the objective engineering characteristics of the in-situ soil body. In addition, advanced geotechnical tests have the disadvantages of long time consumption and high cost, and the two disadvantages also lead to spatial discontinuity of stratum inference and geological parameter interpretation of soil mass. The in-situ test for soil mass is convenient, quick and economical, and is an important means for overcoming the problems. How to realize accurate measurement of soft soil effective stress friction angle based on static cone penetration test adopting in-situ test technology is a challenge faced by the prior art.
It should be noted that the information disclosed in the above background section is only for understanding the background of the application and thus may include information that does not form the prior art that is already known to those of ordinary skill in the art.
Disclosure of Invention
The application mainly aims to overcome the defects of the background technology and provides a soft soil effective stress friction angle measuring method and system based on a pore-pressure static cone penetration test.
In order to achieve the above purpose, the present application adopts the following technical scheme:
a soft soil effective stress friction angle measuring method based on a pore-pressure static cone penetration test comprises the following steps:
performing pore-pressure static cone penetration test on measured in-situ soil bodyCPTu penetration test is tested, and cone tip resistance q of cone probe along with depth change is collected through sensor t Side friction force f s And pore water pressure u 2 ；
According to the collected cone tip resistance q t Side friction force f s And pore water pressure u 2 And (5) interpreting the effective stress friction angle of the measured in-situ soil body.
Further:
the effective stress friction angle phi' is determined according to the following:
φ′≈29.5°·Bq 0.121 ·[0.256+0.336·Bq+log Q] (1-7)
the application range is as follows: phi' is less than or equal to 18 degrees and less than or equal to 45 degrees, and B is less than or equal to 0.05 degrees q A complete clay and clay silty soil with an oversolidification ratio OCR less than 2.5 and less than or equal to 1.0; wherein B is q Is a normalized pore water pressure parameter.
The corrected cone tip drag coefficient Q' is determined according to:
determining the equivalent stress sigma 'according to' e ：
σ v0 For the overburden stress, a' is the effective attractive force,to cover effective stress, overstock ratioσ′ p For effective pre-consolidation stress, Λ= (1-C s /C C ) For plastic volume strain potential, C s Is the rebound index, C C Is the original compression coefficient.
When the plasticization angle β=0, the effective cohesion parameter c '=0, the effective stress friction angle Φ' is determined according to the following equation:
φ′≈29.5°·Bq 0.121 ·[0.256+0.336·Bq+log Q′] (1-10)
the application range is as follows: phi' is less than or equal to 18 degrees and less than or equal to 45 degrees, and B is less than or equal to 0.05 degrees q A total clay and clay silty soil of less than or equal to 1.0.
The equations (1-7) for determining the effective stress friction angle phi' are determined based on the following correlation parameter relationships:
the excess pore water pressure deltau (=u) of the silt and clay can appear 2 -u 0 ) The internal friction angle at the time of no drainage penetration was evaluated using the effective stress limit plastic solution, i.e., cone tip resistance coefficient Q, > 0:
wherein B is q To normalize pore water pressure parameters:
q net (＝q t -σ v0 ) To net total cone tip resistance, q t (＝q c ++ (1-a) u 2) is the tip resistance corrected by the pore pressure; q c A is the unequal area ratio of the probe for actually measured cone tip resistance; sigma (sigma) v0 In order to be able to apply the stress,in order to be able to be covered with an effective stress,u 2 for the measured pore water pressure of the probe shoulder, u 0 Is the static pore water pressure; a 'is the effective attractive force, a' =c '=cot phi', c 'is the effective cohesion parameter, phi' is the effective stress friction angle,
wherein N is q Is the bearing coefficient of the cone tip, N u The pore water pressure bearing coefficient is as follows:
N q ＝K p ·e [(π-2β) ·tanφ′] (1-3)
N u ＝6tanφ′(1+tanφ′) (1-4)
wherein beta is a plasticizing angle (-40 DEG < beta < +30 DEG), and the size of a damage area around the cone tip is defined, K p The passive lateral stress coefficient:
further, when β=0, c '=0, Φ' is obtained with respect to Q and B q The relation between the two is shown as the following formulas 1-6:
and the effective stress friction angle phi' determined from equations (1-7) is an approximate solution to equations (1-6).
According to the normalized pore water pressure parameter B q And the cone tip resistance coefficient Q expressed by the effective stress friction angle phi 'is expressed in the formula (1-6), iterative calculation is carried out by adjusting phi' until Q obtained by calculation is consistent with Q calculated by a static cone penetration test result, and the effective stress friction angle of the soil body can be obtained.
A soft soil effective stress friction angle measurement system based on a Cone Penetration Test (CPTU) comprises a cone penetration test device, a processor and a computer storage medium; the sensor of the CPTu penetration test equipment is connected with the processor and sends the collected cone tip resistance q to the processor t Side friction force f s And pore water pressure u 2 ；
The processor is connected to the computer storage medium, and the computer program stored in the computer storage medium realizes the soft soil effective stress friction angle measuring method according to any one of claims 1 to 6 when executed by the processor.
The application of the soft soil effective stress friction angle measurement method comprises the step of providing measurement data for one or more of stratum mapping, measurement of soft soil effective stress intensity, design of a geotechnical and marine structure foundation base, design of an offshore wind power suction barrel foundation, analysis and evaluation of slope stability and numerical simulation of coupled geotechnical engineering.
The application has the following beneficial effects:
the application provides a soft soil effective stress friction angle measuring method based on a pore-pressure static cone penetration test CPTu, which effectively solves the problems that an advanced geotechnical test is high in cost and long in time consumption, and soil in-situ state information cannot be obtained well. The data of 155 soft clay stations are used for verification, the correlation effect is good, the soft soil effective stress friction angle measurement result is accurate, and the reliability is high.
The soft soil effective stress friction angle measuring method based on the CPTu (pore-pressure static cone penetration test) can be used for quickly measuring on site and generating mass data at the same time so as to make on-site judgment on a survey site, and can map stratum of about 30 meters in one hour. The application can be applied to mature static cone penetration test equipment, has short calculation time, effectively saves cost, fills the blank of static cone penetration test in the aspect of measuring the effective stress intensity of the super-consolidated clay, and has wide application prospect in the aspects of soil intensity measurement and the like. For example, the soil body strength can be calculated in real time by using the measuring result of the application, compared with the traditional indoor high-grade geotechnical test, the cost is lower, the calculating efficiency is higher, and the original engineering characteristics of the soil can be reflected better. The offshore wind power foundation base is designed more effectively, the consumable of the base is reduced, the foundation strength is calculated accurately, and the aims of reducing cost and improving efficiency are achieved.
Other advantages of embodiments of the present application are further described below.
Drawings
FIG. 1 is a schematic illustration of a cone penetration test according to an embodiment of the present application.
FIG. 2 is a plot of effective stress limit plastic solution versus effective stress friction angle (φ') for an embodiment of the application.
Fig. 3 is a comparison of advanced geotechnical test results with CPTu test interpretation results of an embodiment of the present application.
Fig. 4 is a comparison of the results of an advanced geotechnical test (dots) with the results of a CPTu measurement (solid line) of a piezocone penetration test of an embodiment of the present application.
Detailed Description
The following describes embodiments of the present application in detail. It should be emphasized that the following description is merely exemplary in nature and is in no way intended to limit the scope of the application or its applications.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for both a fixing action and a coupling or communication action.
It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing embodiments of the application and to simplify the description by referring to the figures, rather than to indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the application.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the embodiments of the present application, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
The embodiment of the application provides a soft soil effective stress completely based on static sounding test dataFriction angle measuring method, and cone tip resistance (q) changing with depth is obtained by using static cone penetration equipment t ) Side friction resistance (f) s ) And pore water pressure (u) 2 ) And further, the effective stress friction angle of the soft soil is obtained by using the measured parameter information.
According to the embodiment of the application, through carrying out a CPTu penetration test on the measured in-situ soil body, actual measurement parameters are obtained, and then according to the data processing method, the effective stress friction angle of the measured in-situ soil body is interpreted.
Specifically, the basic test method of the Cone Penetration Test (CPTU) is to push a metal cone probe into the ground at a certain speed, and three readings are obtained by using an on-cone force sensor and a pressure sensor at a depth interval of about 0.02 meter, namely depth, cone tip resistance (q t ) Side friction resistance (f) s ) And pore water pressure (u) 2 )。
In the CPTu penetration test, as shown in FIG. 1, the corresponding sensors on the CPTu read spatially continuous depth-dependent cone tip resistance (q t ) Side friction resistance (f) s ) And pore water pressure (u) 2 )。
The silt and clay will develop a super pore water pressure (deltau (=u) 2 -u 0 ) > 0), the effective stress limit plastic solution, i.e., cone tip resistance coefficient (Q), was used to evaluate the internal friction angle without drainage penetration:
wherein B is q To normalize pore water pressure parameters:
q net (＝q t -σ v0 ) G is the net total cone tip resistance t (＝g c ++ (1-a) u 2) is the tip resistance corrected by the pore pressure; q c Is actually measured asA is the unequal area ratio of the probe; sigma (sigma) v0 In order to be able to apply the stress,in order to be able to be covered with an effective stress,u 2 for the measured pore water pressure of the probe shoulder, u 0 Is the static pore water pressure; a 'is the effective attractive force, a' =c '=cot phi', c 'is the effective cohesion parameter, phi' is the effective stress friction angle,
wherein N is q Is the bearing coefficient of the cone tip, N u The pore water pressure bearing coefficient is as follows:
N q ＝K p ·e [(π-2γ)·tanφ′ ] (1-3)
N u ＝6tanφ′(1+tanφ′) (1-4)
wherein beta is a plasticizing angle (-40 DEG < beta < +30 DEG), and the size of a damage area around the cone tip is defined, K p The passive lateral stress coefficient:
further, when β=0, c '=0, Φ' is obtained with respect to Q and B q The relationship between the following formulas 1 to 6 and fig. 2:
the approximate solutions for formulas 1-6 are:
φ′≈29.5°·Bq 0.121 ·[0.256+0.336·Bq+log Q] (1-7)
the application range of formulas 1-7 is: phi' is less than or equal to 18 degrees and less than or equal to 45 degrees, and B is less than or equal to 0.05 degrees q A total clay and clay-based silt with moderate hardness (OCR < 2.5) of less than or equal to 1.0.
To apply equations 1-7 to over-consolidated clays and silts, an over-consolidation ratio (OCR) describing soil consolidation is introduced into the Q expression, defining a corrected cone tip drag coefficient (Q'):
in which sigma' e Is equivalent stress:
for the oversolidification ratio, σ' p Is effective pre-consolidation stress; Λ= (1-C s /C C ) To be plastic volume strain potential, empirically summarized, the representative value of natural clay is 0.8, with values between 0.7 and 0.9 for low to medium sensitivity clays, and can be as high as 1 for highly structural and sensitive clays; c (C) s Is the rebound index, C C Is the original compression coefficient.
Substituting the corrected tip drag coefficient for the tip drag coefficient, when β=0, c '=0, the effective stress friction angle Φ' can be expressed as:
φ′≈29.5°·Bq 0.121 ·[0.256+0.336·Bq+log Q′] (1-10)
the application range of formulas 1-10 is: phi' is less than or equal to 18 degrees and less than or equal to 45 degrees, and B is less than or equal to 0.05 degrees q A total clay and clay silty soil of less than or equal to 1.0.
Alternative embodiment
Derived by normalizing the pore water pressure parameter (B q ) And (2) after the expression 1-6 of the cone tip resistance coefficient (Q) expressed by the effective stress friction angle (phi '), carrying out iterative calculation by adjusting phi', and obtaining the effective stress friction angle of the soil body when the Q obtained by the expression 1-6 is consistent with the Q calculated by the static cone penetration test result.
Experiment verification
The data of 155 soft clay stations are used for verification, and the correlation effect is good.
Fig. 3 shows the results of the advanced geotechnical test in comparison with the results of the CPTu test interpretation of the present embodiment.
The CPTu can generate mass data while rapidly measuring in real time on site so as to make in-situ judgment on a survey site, and can map about 20 meters of stratum in one hour. The effective stress intensity of the soft clay is calculated by systematically researching the reading reaction of the soft clay in CPTu, analyzing and summarizing the data of the test and combining with the ultimate plastic theory.
The scheme can be applied to mature static cone penetration equipment, has short calculation time, effectively saves cost, fills up the blank of the static cone penetration in the aspect of measuring the effective stress intensity of the super-consolidated clay, and has wide application prospect in the aspects of soil intensity measurement and the like.
FIG. 4 shows the results of one embodiment of the present application, which is obtained by combining the cone tip drag coefficient (Q) obtained by the cone penetration test CPTu with the normalized pore water pressure parameter (B q ) The measuring method of the application is used for obtaining the section of the change of the effective stress friction angle of clay along with the penetration depth, which is interpreted by the static sounding test, comparing the numerical value with the indoor high-grade geotechnical test result, and finding that the consistency is better, i.e. the measuring method of the application is reliable. Meanwhile, the penetration depth of the in-situ test is deeper, namely the soil state changes more along with the penetration depth, and the indoor unit test needs to take a plurality of groups of measurement. The above comparison highlights the advantages of the method of the application.
Figure 4 advanced geotechnical test results (dots) are compared with results calculated by the CPTu of the piezocone penetration test (solid lines).
The application has the technical advantages that:
1. mass data are generated while the real-time rapid measurement is performed on site, so that the on-site judgment is performed on the survey site, the stratum of about 20 meters can be mapped in one hour, and the method is particularly useful for surveying large geotechnical engineering projects or processing soil conditions with strong variability.
2. Compared with the indoor high-grade geotechnical test, the method has low cost, convenience and rapidness.
3. The reading reaction of the soft soil in the static sounding test is researched systematically, and the test reading data can be analyzed and summarized to calculate the effective stress intensity of the soft soil.
4. The application can be applied to mature static cone penetration equipment, has short calculation time and effectively saves cost.
The application of the application also comprises:
1. the method can realize large-scale continuous calculation of the effective stress friction angle of the soil layer, and is used for designing a foundation base (a single pile type offshore wind power base) of a geotechnical and marine structure.
2. Designing a foundation of the offshore wind power suction barrel.
3. And (5) analyzing the stability of the side slopes such as coasts.
4. The coupled geotechnical engineering numerical simulation method provides constitutive parameters.
The application can calculate the soil intensity in real time, has lower cost and higher calculation efficiency compared with the traditional indoor high-grade geotechnical test, and can reflect the original engineering characteristics of the soil.
According to the application, the offshore wind power foundation base is designed more effectively, the consumable materials of the base are reduced, the foundation strength is calculated accurately, and the aims of reducing cost and enhancing efficiency are achieved.
The embodiments of the present application also provide a storage medium storing a computer program which, when executed, performs at least the method as described above.
The embodiment of the application also provides a control device, which comprises a processor and a storage medium for storing a computer program; wherein the processor is adapted to perform at least the method as described above when executing said computer program.
The embodiments of the present application also provide a processor executing a computer program, at least performing the method as described above.
The storage medium may be implemented by any type of volatile or non-volatile storage device, or combination thereof. The nonvolatile Memory may be a Read Only Memory (ROM), a programmable Read Only Memory (PROM, programmable Read-Only Memory), an erasable programmable Read Only Memory (EPROM, erasableProgrammable Read-Only Memory), an electrically erasable programmable Read Only Memory (EEPROM, electricallyErasable Programmable Read-Only Memory), a magnetic random Access Memory (FRAM, ferromagneticRandom Access Memory), a Flash Memory (Flash Memory), a magnetic surface Memory, an optical disk, or a compact disk Read Only (CD-ROM, compact Disc Read-Only Memory); the magnetic surface memory may be a disk memory or a tape memory. The volatile memory may be random access memory (RAM, random Access Memory), which acts as external cache memory. By way of example, and not limitation, many forms of RAM are available, such as static random access memory (SRAM, static Random Access Memory), synchronous static random access memory (SSRAM, synchronousStatic Random Access Memory), dynamic random access memory (DRAM, dynamic Random AccessMemory), synchronous dynamic random access memory (SDRAM, synchronous Dynamic Random AccessMemory), double data rate synchronous dynamic random access memory (ddr SDRAM, double Data RateSynchronous Dynamic Random Access Memory), enhanced synchronous dynamic random access memory (ESDRAM, enhanced Synchronous Dynamic Random Access Memory), synchronous link dynamic random access memory (SLDRAM, syncLink Dynamic Random Access Memory), direct memory bus random access memory (DRRAM, direct Rambus Random Access Memory). The storage media described in embodiments of the present application are intended to comprise, without being limited to, these and any other suitable types of memory.
In the several embodiments provided by the present application, it should be understood that the disclosed systems and methods may be implemented in other ways. The above described device embodiments are only illustrative, e.g. the division of the units is only one logical function division, and there may be other divisions in practice, such as: multiple units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed. In addition, the various components shown or discussed may be coupled or directly coupled or communicatively coupled to each other via some interface, whether indirectly coupled or communicatively coupled to devices or units, whether electrically, mechanically, or otherwise.
The units described as separate units may or may not be physically separate, and units displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units; some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in each embodiment of the present application may be integrated in one processing unit, or each unit may be separately used as one unit, or two or more units may be integrated in one unit; the integrated units may be implemented in hardware or in hardware plus software functional units.
Those of ordinary skill in the art will appreciate that: all or part of the steps for implementing the above method embodiments may be implemented by hardware associated with program instructions, where the foregoing program may be stored in a computer readable storage medium, and when executed, the program performs steps including the above method embodiments; and the aforementioned storage medium includes: a mobile storage device, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk or an optical disk, or the like, which can store program codes.
Alternatively, the above-described integrated units of the present application may be stored in a computer-readable storage medium if implemented in the form of software functional modules and sold or used as separate products. Based on such understanding, the technical solutions of the embodiments of the present application may be embodied in essence or a part contributing to the prior art in the form of a software product stored in a storage medium, including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a removable storage device, ROM, RAM, magnetic or optical disk, or other medium capable of storing program code.
The methods disclosed in the method embodiments provided by the application can be arbitrarily combined under the condition of no conflict to obtain a new method embodiment.
The features disclosed in the several product embodiments provided by the application can be combined arbitrarily under the condition of no conflict to obtain new product embodiments.
The features disclosed in the embodiments of the method or the apparatus provided by the application can be arbitrarily combined without conflict to obtain new embodiments of the method or the apparatus.
The foregoing is a further detailed description of the application in connection with the preferred embodiments, and it is not intended that the application be limited to the specific embodiments described. It will be apparent to those skilled in the art that several equivalent substitutions and obvious modifications can be made without departing from the spirit of the application, and the same should be considered to be within the scope of the application.

Claims (8)

1. The soft soil effective stress friction angle measuring method based on the pore-pressure static cone penetration test is characterized by comprising the following steps of:
carrying out a CPTu penetration test on a measured in-situ soil body by a pore-pressure static cone penetration test, and collecting cone tip resistance q of a cone probe along with depth change through a sensor t Side friction force f s And pore water pressure u 2 ；
According to the collected cone tip resistance q t Side friction force f s And pore water pressure u 2 And (5) interpreting the effective stress friction angle of the measured in-situ soil body.
2. The method for measuring effective stress friction angle of soft soil according to claim 1, wherein the effective stress friction angle Φ' is determined according to the following formula:
φ′≈29.5°·Bq 0.121 ·[0.256+0.336·Bq+log Q] (1-7)
the application range is as follows: phi' is less than or equal to 18 degrees and less than or equal to 45 degrees, and B is less than or equal to 0.05 degrees q OCR with oversolidification ratio less than or equal to 1.0<2.5 whole clay and clay silts; wherein B is q Is a normalized pore water pressure parameter.
3. The soft soil effective stress friction angle measurement method of claim 2, wherein the corrected cone tip drag coefficient Q' is determined according to the following equation:
determining the equivalent stress sigma 'according to' e ：
σ v0 For the overlying stress, a' is the effective attractive force, < ->To cover the effective stress, the oversolidation ratio +.>For effective pre-consolidation stress, Λ= (1-C s /C C ) For plastic volume strain potential, C s Is the rebound index, C C Is the original compression coefficient.
4. A soft soil effective stress friction angle measuring method according to claim 3, wherein when the plasticizing angle β=0 and the effective cohesion parameter c '=0, the effective stress friction angle Φ' is determined according to the following formula:
φ′≈29.5°·Bq 0.121 ·[0.256+0.336·Bq+log Q′] (1-10)
the application range is as follows: phi' is less than or equal to 18 degrees and less than or equal to 45 degrees, and B is less than or equal to 0.05 degrees q A total clay and clay silty soil of less than or equal to 1.0.
5. A soft soil effective stress friction angle measuring method according to any one of claims 2 to 4, characterized in that the formula (1-7) for determining the effective stress friction angle Φ' is determined based on the following correlation parameter relation:
the excess pore water pressure deltau (=u) of the silt and clay can appear 2 -u 0 )>0, evaluating an internal friction angle when no drainage is penetrated by utilizing an effective stress limit plastic solution, namely a cone tip resistance coefficient Q:
wherein B is q To normalize pore water pressure parameters:
q net (＝q t -σ v0 ) To net total cone tip resistance, q t (＝q c ++ (1-a) u 2) is the tip resistance corrected by the pore pressure; q c A is the unequal area ratio of the probe for actually measured cone tip resistance; sigma (sigma) v0 In order to be able to apply the stress,in order to be able to be covered with an effective stress,u 2 for the measured pore water pressure of the probe shoulder, u 0 Is the static pore water pressure; a 'is the effective attractive force, a' =c '=cot phi', c 'is the effective cohesion parameter, phi' is the effective stress friction angle,
wherein N is q Is the bearing coefficient of the cone tip, N u The pore water pressure bearing coefficient is as follows:
N q ＝K p ·e [(π-2β)·tanφ′] (1-3)
N u ＝6 tanφ′(1+tanφ′) (1-4)
wherein beta is plasticizing angle (-40 deg.)<β<+30°), defining the size, K, of the fracture zone around the tip of the cone p The passive lateral stress coefficient:
further, when β=0, c '=0, Φ' is obtained with respect to Q and B q The relation between the two is shown as the following formulas 1-6:
and the effective stress friction angle phi' determined from equations (1-7) is an approximate solution to equations (1-6).
6. The soft soil effective stress friction angle measuring method according to claim 5, wherein the normalized pore water pressure parameter B is used for q And the cone tip resistance coefficient Q expressed by the effective stress friction angle phi 'is expressed in the formula (1-6), iterative calculation is carried out by adjusting phi' until Q obtained by calculation is consistent with Q calculated by a static cone penetration test result, and the effective stress friction angle of the soil body can be obtained.
7. A soft soil effective stress friction angle measuring system based on a hydrostatic Cone Penetration Test (CPTU), which is characterized by comprising a CPTu penetration test device, a processor and a computer storage medium; the sensor of the CPTu penetration test equipment is connected with the processor and sends the collected cone tip resistance q to the processor t Side friction force f s And pore water pressure u 2 ；
The processor is connected to the computer storage medium, and the computer program stored in the computer storage medium realizes the soft soil effective stress friction angle measuring method according to any one of claims 1 to 6 when executed by the processor.
8. Use of a soft soil effective stress friction angle measurement method according to any one of claims 1 to 6, comprising providing measurement data for one or more of formation mapping, measurement of soft soil effective stress intensity, design of geotechnical, marine structure foundation base, design of offshore wind power suction bucket foundation, slope stability analysis evaluation, coupled geotechnical engineering numerical simulation.
CN202310951544.5A 2023-07-31 2023-07-31 Soft soil effective stress friction angle measurement method based on pore-pressure static cone penetration test Pending CN116950030A (en)

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