Shear wave velocity estimation method based on piezocone penetration test

Abstract

The invention belongs to the technical field of geotechnical engineering testing and site investigation, and provides a shear wave velocity estimation method based on a piezocone penetration test, which can accurately and conveniently estimate the shear wave velocity. The method specifically comprises the following steps of S1, carrying out a pore pressure static sounding test on a plurality of drill holes in a site, and obtaining pore pressure static sounding basic parameters and shear wave velocity of each drill hole tested in the depth direction, S2, interpreting derived parameters according to the pore pressure static sounding basic parameters, S3, carrying out soil layer division, soil type identification and soil body type judgment, and S4, carrying out soil layer classification, soil type identification and soil body type judgment. S4, selecting data tested by the same soil body type as an analysis object, performing fitting analysis on the scatter diagrams of the cone tip resistance and the shear wave velocity of the piezocone penetration test to obtain a fitting formula, and S5, obtaining normalized cone tip resistance and normalized shear wave velocity based on the cone tip resistance and the shear wave velocity, substituting the normalized cone tip resistance and the normalized shear wave velocity into the fitting formula in the step S4, and introducing a soil classification index to obtain a soil classification result. And obtaining a calculation expression of the optimal estimation shear wave.

Description

Technical Field

[0001] The invention discloses a shear wave velocity estimation method based on a pore pressure static penetration test, belonging to the technical field of geotechnical engineering testing and site investigation. Background Art

[0002] Shear wave velocity refers to the propagation speed of the vibration shear wave in the soil, reflecting the dynamic response characteristics of the small strain shear modulus of the soil. The small strain shear modulus of the soil is closely related to the soil shear wave velocity. It is a basic parameter to characterize the dynamic characteristics of the soil and plays an important role in earthquake engineering and geotechnical engineering problems such as soil deformation prediction, earthquake site response analysis and determination of dynamic foundation design parameters. Therefore, as a basic soil property parameter in geotechnical engineering, shear wave velocity is widely used in earthquake site response analysis, site category identification, evaluation of liquefaction potential and gravity, etc. Compared with other geotechnical parameters, the shear wave velocity test parameter also has the following advantages, such as independence from other soil properties, such as fine particle content and particle compressibility, that is, the influence of factors such as fine particle content and particle compressibility can be included through the shear wave velocity parameter index. At the same time, the shear wave velocity test can be carried out indoors or outdoors. Therefore, the determination of shear wave velocity is very important in the field of geotechnical engineering.

[0003] Since in-situ testing can directly provide the in-situ characteristics of the rock and soil body and obtain the engineering property indicators of the on-site soil layer, in-situ testing methods are more commonly used in engineering, including the cross-hole method, the down-hole method and the transient Rayleigh wave method. Although direct testing of the shear wave velocity is the most ideal, the cost of professional equipment and professional technicians required in the test process is relatively high, which is not economically feasible for general projects in terms of cost. Therefore, it is very important to accurately estimate the shear wave velocity. In-situ penetration tests are usually used to estimate the shear wave velocity. Compared with standard penetration tests, static penetration tests have gradually become the most important in-situ tests, which can provide approximately continuous geotechnical parameter profiles, especially the emergence of pore pressure static penetration tests, which can test the pore water pressure of the soil body, and are in line with relevant international standards, broadening its scope of application and achieving good results.

[0004] The invention patent (authorization announcement number CN 109187744 B) discloses a method for estimating shear wave velocity based on static penetration test. This method uses the modified static penetration cone tip resistance and porosity ratio to predict the shear wave velocity, and this method requires different soil types to be predicted separately. However, natural soil layers are not completely uniform and consistent. There are often interlayers, such as sand and powder interlayers, or thin clay layers in sand, or thin sand layers in clay layers. The interlayers cannot be accurately identified by mechanical property parameters such as cone tip resistance. When a single soil layer formula is used, the prediction results will be very biased, and the applicability is greatly reduced.

[0005] However, natural soil layers have large anisotropy and complex and changeable sedimentary characteristics. The porosity ratio cannot be directly interpreted based on static penetration testing. In addition, the prediction of porosity ratio based on static penetration testing cannot achieve good results. This is mainly because the porosity ratio is a basic physical indicator of soil, while the static penetration testing parameters are mainly mechanical property indicators of soil. The porosity ratio usually requires indoor testing of borehole sampling. Due to the introduction of the porosity ratio, the relevant results given will have certain limitations in actual engineering. Therefore, it is necessary to propose a new accurate and convenient shear wave velocity estimation method. Summary of the invention

[0006] In view of the problems of high cost, long construction period, inaccurate and unsuitable existing shear wave velocity estimation methods in existing in-situ shear wave velocity determination, the present invention proposes a shear wave velocity estimation method based on pore pressure static penetration test, which can estimate the shear wave velocity more accurately and conveniently.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a shear wave velocity estimation method based on pore pressure static penetration test, comprising the following steps:

[0008] S1. Conduct pore pressure static penetration tests on multiple boreholes on site to obtain the basic parameters of pore pressure static penetration and shear wave velocity V of each borehole tested along the depth direction. s The basic parameters of pore pressure static penetration include cone tip resistance q t , side wall friction f s , pore water pressure u2;

[0009] S2. Derived parameters are interpreted based on the basic parameters of pore pressure static penetration test, wherein the derived parameters include friction ratio R f , normalized friction ratio F r , pore pressure parameter B q , Soil Classification Index I c , Normalized cone tip resistance Q tn , normalized shear wave velocity V s1 ;

[0010] S3, combined with geotechnical tests and geological data, based on the cone tip resistance q t , side wall friction f s , pore water pressure u2, friction ratio R f , pore pressure parameter B q Divide soil layers based on soil classification index I c Identify soil types and determine soil types;

[0011] S4, through step S3, the data tested by the same soil type are selected as the analysis object, and the data are preprocessed, including the removal of abnormal points based on the probability statistics related theory, and then three different types of fitting functions, namely exponential function, power function and linear function, are selected to analyze the cone tip resistance q of the pore pressure static penetration test. t and shear wave velocity V s Perform fitting analysis on the scatter plot to obtain the fitting formula;

[0012] S5. Cone tip resistance q in basic parameters of pore pressure static penetration t and shear wave velocity V s , considering the effective overburden pressure σ′ v0 The influence of and dimensionless principle, the normalized cone tip resistance Q is obtained tn and the normalized shear wave velocity V s1 , substitute into the fitting formula in step S4, and convert the soil classification index I c Introduce and obtain the best estimate of the shear wave velocity V sE The computational expression of .

[0013] The pore pressure static penetration test in step S1 adopts the seismic wave pore pressure static penetration test, and the specific method is:

[0014] A set of basic parameter data of pore pressure static penetration is collected every 0.05m along the depth of each borehole, and the penetration is stopped every 1m to start seismic wave testing and collect the recovered shear wave velocity V s Parameter data.

[0015] When the seismic wave pore pressure static penetration test cannot be carried out on site, the pore pressure static penetration test in step S1 can be carried out in the following two ways:

[0016] a) Perform shear wave velocity test on the pore pressure static penetration test hole at the same time, and use the shear wave velocity test hole data obtained from the shear wave velocity test as the shear wave velocity test value used in subsequent calculations;

[0017] b) If the shear wave velocity test is not carried out simultaneously on the pore pressure static penetration test hole, the shear wave velocity test hole data of the borehole closest to the pore pressure static penetration test hole is selected as the shear wave velocity test hole data for subsequent calculations, and the distance between the nearest borehole and the hole is less than 0.5m.

[0018] The step S2 is to interpret the derived parameters according to the basic parameters of the pore pressure static penetration test as follows:

[0019] Basic parameters: cone tip resistance q t , side wall friction f s , pore water pressure u2;

[0020] Derived parameter: Friction ratio Rf , normalized friction ratio F r , pore pressure parameter B q , Soil Classification Index I c , Normalized cone tip resistance Q tn , normalized shear wave velocity V s1 ;

[0021] Friction ratio R f The expression is:

[0022] R f =f s / q t ×100% (1)

[0023] Normalized friction ratio F r The expression is:

[0024] F r =f s / (q t -σ v0 ) (2)

[0025] In the formula, σ v0 is the overburden pressure on the soil layer;

[0026] Pore ​​pressure parameter B q The expression is:

[0027] B q =(u2-u0) / (q t -σ v0 ) (3)

[0028] Where u0 is the hydrostatic pressure;

[0029] Soil Classification Index I c The calculation method is as follows:

[0030] Robertson's soil classification index is denoted as I c,RW ;

[0031] The soil classification index proposed by Been and Jefferies is denoted as I c,BJ ;

[0032] The expressions are:

[0033]

[0034] In the formula, Q t =(q t -σ vo ) / σ′ vo ,σ′ v0 is the effective overburden pressure; where I c,BJ Contains pore pressure parameter Bq , which can better characterize the presence or absence of clay soil;

[0035] Normalized cone tip resistance Q tn The expression is:

[0036]

[0037] In the formula, σ′ v0 is the effective overburden pressure; n is the stress index;

[0038] Specifically, n = 0.381I c +0.05(σ′ v0 / p a )-0.15≤1; where I c is the soil classification index; p a is the reference pressure, i.e. atmospheric pressure;

[0039] Based on the shear wave velocity V s Test parameter data, interpret the derived parameter normalized shear wave velocity V s1 as follows:

[0040]

[0041] Through the above interpretation method, a derived parameter group corresponding to the cone tip resistance at every 1m interval along the depth direction can be obtained.

[0042] The specific steps of step S3 for determining the soil type are as follows:

[0043] Combined with geotechnical tests and geological data, the soil layers are divided, and then each layer is divided into multiple sub-layers at intervals of 1m. The mean value of each parameter, including basic parameters and derived parameters, is calculated under each layer, which is used for the subsequent prediction of the pore pressure static penetration data points for shear wave velocity. The soil type is further clarified and verified through the soil classification map and soil classification index, and the sub-layer in each layer is normalized to the cone tip resistance Q tn and normalized friction ratio F r The data is projected onto the soil classification map, and the soil classification index I calculated based on the above sub-layers is c Identify soil types.

[0044] The fitting formula obtained in step S4 is:

[0045] Use the exponential function model to calculate V s1 / Q tn and I c,BJ The scatter plot is analyzed by exponential function fitting, and the specific formula is:

[0046]

[0047] Where a and b are fitting coefficients.

[0048] In step S5, the normalized shear wave velocity V can be obtained according to formula (8): s1 The expression is:

[0049]

[0050] Substituting equation (8) into equation (7) yields the best estimate of the shear wave velocity V sE Calculate the expression:

[0051]

[0052] Substituting equation (6) into equation (10) yields the best estimate of the shear wave velocity V sE Calculate the expression:

[0053]

[0054] The shear wave velocity estimation method based on pore pressure static penetration test provided by the present invention can accurately and comprehensively reflect soil characteristics, and provide a powerful calculation method for dynamic characteristic analysis of earthquake engineering sites and shear wave velocity testing and estimation in geotechnical engineering investigation practice.

[0055] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the contents pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0057] Figure 1 It is a schematic diagram of the process of the present invention;

[0058] Figure 2 An approximate continuous variation curve diagram of basic parameters of pore pressure static penetration testing and a shear wave velocity scatter diagram provided by an embodiment of the present invention;

[0059] Figure 3 Robertson soil classification diagram provided by an embodiment of the present invention;

[0060] Figure 4 Been and Jefferies soil classification diagram provided for embodiments of the present invention;

[0061] Figure 5A schematic diagram of a shear wave velocity prediction curve for a cohesionless soil layer provided by an embodiment of the present invention;

[0062] Figure 6 A schematic diagram of the histogram distribution of shear wave velocity accuracy provided by an embodiment of the present invention;

[0063] Figure 7 A comparison chart of the shear wave velocity estimation result and the measured value provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0065] The present invention provides a shear wave velocity estimation method based on pore pressure static penetration test, comprising: Figure 1 Steps shown.

[0066] S1. Carry out multiple seismic wave pore pressure static penetration tests in multiple boreholes on the site (the seismic wave pore pressure static penetration test can test the pore pressure static penetration parameters and shear wave velocity at the same time), collect a set of basic pore pressure static penetration parameter data every 0.05m along the depth of each borehole, and stop penetration every 1m to start seismic wave testing and collect and recover shear wave velocity V s Parameter data, obtain the approximate continuous change curve of the basic parameters of the pore pressure static penetration test and the shear wave velocity V for each borehole tested along the depth direction s Scatter plot, the basic parameters of pore pressure static penetration include cone tip resistance q t , side wall friction f s , pore water pressure u2;

[0067] If the site cannot carry out seismic wave borehole pressure static penetration test, a shear wave velocity test can be carried out simultaneously with the borehole pressure static penetration test hole, such as the downhole DHT test, and the shear wave velocity test will be used as the shear wave velocity test hole data as the shear wave velocity test value used in subsequent calculations; if the shear wave velocity test is not carried out simultaneously with the borehole pressure static penetration test hole, the shear wave velocity test hole data of the nearest borehole (less than 0.5m away) to the borehole pressure static penetration test hole will be selected as the shear wave velocity test hole data for subsequent calculations.

[0068] S2. Derived parameters are interpreted based on the basic parameters of pore pressure static penetration test, wherein the derived parameters include friction ratio R f , normalized friction ratio F r , pore pressure parameter Bq , Soil Classification Index I c , Normalized cone tip resistance Q tn , normalized shear wave velocity V s1 ;

[0069] The details are as follows:

[0070] Basic parameters: cone tip resistance q t , side wall friction f s , pore water pressure u2;

[0071] Derived parameter: Friction ratio R f , normalized friction ratio F r , pore pressure parameter B q , Soil Classification Index I c , Normalized cone tip resistance Q tn , normalized shear wave velocity V s1 ;

[0072] Friction ratio R f The expression is:

[0073] R f =f s / q t ×100% (1)

[0074] Normalized friction ratio F r The expression is:

[0075] F r =f s / (q t -σ v0 ) (2)

[0076] In the formula, σ v0 is the overburden pressure on the soil layer;

[0077] Pore ​​pressure parameter B q The expression is:

[0078] B q =(u2-u0) / (q t -σ v0 ) (3)

[0079] Where u0 is the hydrostatic pressure;

[0080] Soil Classification Index I c The calculation method is as follows:

[0081] Robertson's soil classification index is denoted as I c,RW ;

[0082] The soil classification index proposed by Been and Jefferies is denoted as Ic,BJ ;

[0083] The expressions are:

[0084]

[0085] In the formula, Q t =(q t -σ vo ) / σ′ vo , σ vo ,σ′ vo are respectively the overburden pressure on the soil layer and the effective overburden pressure; c,BJ Contains pore pressure parameter B q , which can better characterize the presence or absence of clay soil;

[0086] Normalized cone tip resistance Q tn The expression is:

[0087]

[0088] In the formula, σ′ v0 is the effective overburden pressure; n is the stress index;

[0089] Specifically, n = 0.381I c +0.05(σ′ v0 / p a )-0.15≤1; where I c is the soil classification index; p a is the reference pressure, which is the atmospheric pressure 0.1MPa;

[0090] Based on the shear wave velocity V s Test parameter data, interpret the derived parameter normalized shear wave velocity V s1 as follows:

[0091]

[0092] Through the above interpretation method, a derived parameter group corresponding to the cone tip resistance at every 1m interval along the depth direction can be obtained.

[0093] S3, based on cone tip resistance q t , side wall friction f s , pore water pressure u2, friction ratio R f , pore pressure parameter B q and shear wave velocity V s , plot q t、 f s、 u 2、 R f , B q 、V sAlong the depth variation curve profile, combined with geotechnical tests and geological data, the soil layers are divided according to the "Geotechnical Engineering Investigation Code" GB 50021-2009 and the "Pore Pressure Static Penetration Test Technical Code" T / CCES1-2017. Then each layer is divided into multiple sub-layers at intervals of 1m. Under each layer, the mean value of each parameter including basic parameters and derived parameters is calculated, which is used for the subsequent prediction of the porostatic penetration test data points in the shear wave velocity. The soil type is further clarified and verified through the soil classification map and soil classification index, and the sub-layer Q in each layer is divided into multiple sub-layers. tn and F r The data is projected onto the soil classification map, and the soil classification index I calculated based on the above sub-layers is c Identify soil types and determine soil body type.

[0094] S4, through step S3, the data tested by the same soil type are selected as the analysis object, and the data are preprocessed, including the removal of abnormal points based on the probability statistics related theory, and then three different types of fitting functions, namely exponential function, power function and linear function, are selected to analyze the cone tip resistance q of the pore pressure static penetration test. t and shear wave velocity V s Perform fitting analysis on the scatter plot to obtain the fitting formula;

[0095] Obtaining the fitting formula:

[0096] Soil classification index I is not considered c When the influence of Q is considered, three fitting functions, namely exponential function model, power function model and linear function model, are selected. tn is the normalized cone tip resistance Q of the horizontal axis tn and the normalized shear wave velocity V s1 Perform fitting analysis on the scatter plot to obtain the corresponding formula;

[0097] When considering soil classification index I c The influence of c,RW and I with pore pressure parameters c,BJ , respectively as the horizontal axis, and the vertical axis is the normalized cone tip resistance Q tn and the normalized shear wave velocity V s1 The ratio of the two models is plotted, and a scatter plot is drawn. The exponential function model, power function model, and linear function model are selected for fitting analysis to obtain the corresponding formula.

[0098] According to the determination coefficient and performance analysis, it is found that the exponential function model has better fitting effect and higher accuracy than the power function model and the linear function model. c The impact is greater than that without considering I c The model with the best effect is better when considering soil classification index I cWhen the influence of pore pressure is considered, the I c,BJ The model effect is better, and the formula is simple and practical. Therefore, the exponential function model is used to calculate Q tn / V s1 and I c,BJ The scatter plot is analyzed by exponential function fitting, and the specific formula is:

[0099]

[0100] Where a and b are fitting coefficients.

[0101] S5. Cone tip resistance q in basic parameters of pore pressure static penetration t and shear wave velocity V s , considering the effective overburden pressure σ′ v0 The influence of and dimensionless principle, the normalized cone tip resistance Q is obtained tn and the normalized shear wave velocity V s1 , substitute into the fitting formula (8) in step S4, and convert the soil classification index I c Introduce and obtain the best estimate of the shear wave velocity V s The calculation expression is:

[0102] According to formula (8), the normalized shear wave velocity V s1 The expression is:

[0103]

[0104] Substituting equation (8) into equation (7) yields the best estimate of the shear wave velocity V sE Calculate the expression:

[0105]

[0106] Substituting equation (6) into equation (10) yields the best estimate of the shear wave velocity V sE Calculate the expression:

[0107]

[0108] The steps of the present invention are described in detail below in conjunction with the embodiment data:

[0109] Specifically, in a specific embodiment of the present invention: according to the above method step S1, the basic parameters of the pore pressure static penetration test are obtained as shown in Table 1 (because the basic parameters are measured once every 0.05m, the embodiment uses 20m deep drilling test data for illustration, and the amount of data is too large, and only the shear wave velocity V measured every 1m is shown in Table 1 s Basic parameter data at the time of

[0110] Table 1 Basic parameters and shear wave velocity of pore pressure static penetration

[0111]

[0112] The derived parameters interpreted according to step S2 are shown in Table 2:

[0113] Table 2 Derived parameters of pore pressure static penetration test

[0114]

[0115]

[0116] According to the data in Table 1 and Table 2, the cone tip resistance q is plotted. t , side wall friction f s , pore water pressure u2, friction ratio R f , pore pressure parameter B q , shear wave velocity V s The profile along the depth variation curve, such as Figure 2 As shown, including the cone tip resistance q t , side wall friction f s , pore water pressure u2, friction ratio R f , pore pressure parameter B q , shear wave velocity V s , to divide the soil layers, such as Figure 3 As shown, the soil layers can be preliminarily divided into:

[0117] i) Fill (0-1.2m), the average cone tip resistance is 1.3MPa;

[0118] ii) sand (1.2-4m), silt and sand (4-16m), with an average cone tip resistance of 3.5MPa;

[0119] iii) Silty sand (16-20 m), the cone tip resistance continues to increase with depth and exceeds 5 MPa.

[0120] It can be seen that in the sand-silt mixture, compared with fine-grained soils such as soft clay, only a small amount of pore water pressure was observed during the penetration process of the pore pressure static penetration test. This is because in the sand layer, the penetration process is completely drained, while in the silt layer, the penetration process is in a semi-drained state, which can be seen through B q The positive and negative values ​​of B can also effectively identify sand and powder layers or drainage and undrained conditions. q When it is positive, it means that there is excess pore water pressure and there is a certain amount of clay in the soil layer. q When it is a negative value, it means that it is in a negative pore pressure state, shear expansion occurs, and the soil layer does not contain clay, but is sandy soil.

[0121] The friction ratio F of the pore pressure static penetration test data of each sub-layer is normalizedr , Normalized cone tip resistance Q tn Projected onto the two soil classification maps, such as Figure 4-6 As shown in the figure, it can be seen that most of the data points fall into areas 4, 5, and 6, which include the intermediate soils from silt mixture to silt sand. At the same time, it can be seen that the soil classification diagram of Been and Jefferies uses I c,BJ Classification index is divided into categories, including pore pressure parameter B q , so that the pore pressure parameters are well correlated with the behavior of such sediments, by I c,BJ The classification diagram of is more in line with the situation of this type of strata, indicating that the pore pressure parameter is more sensitive to transitional soils such as clay, cohesionless soil, and silty soil, and can be better used for soil layer division. Therefore, if the pore pressure parameter or the I containing the pore pressure parameter is introduced into the shear wave velocity estimation expression c,BJ When the soil type is better,

[0122] In step S3, the present embodiment selects the data tested on the type of soil without cohesion as the analysis object, and processes the data by using the outlier method in probability statistics. When constructing the correlation relationship, the dimensionless variable theory is generally used to construct the correlation model. Considering the convenience of the formula, three fitting parameters, namely, exponential function, power function and linear function, are used for analysis. Finally, the best estimated shear wave velocity V obtained by the present invention is substituted into sE Calculate the expression:

[0123]

[0124] Analytical Verification:

[0125] According to the above calculation formula, the best estimated shear wave velocity V is obtained for twenty corresponding points every 1 m in the borehole. sE (Unit: m / s), compare it with the measured shear wave velocity Vs and calculate the absolute value of the relative error [(predicted value - test value) / test value], as shown in Table 3:

[0126] Table 3 Relative error between the best estimated shear wave velocity and the measured shear wave velocity

[0127]

[0128]

[0129] In order to verify the rationality and uniformity of the method of the present invention, the best estimated shear wave velocity V sE Compared with the measured V sM (That is, V given in Table 1 s ) is recorded as K(V sE / V sM ), whose histogram is as follows Figure 5As shown, it can be seen that the distribution can be described by a normal distribution, indicating the rationality of the prediction model results.

[0130] In order to further verify the accuracy of the method of the present invention, the test hole of the above embodiment (conducting the pore pressure static penetration test and the downhole shear wave velocity test at the same time) was selected for analysis. Figure 6 The variation curves of the shear wave velocity along the depth estimated by the method of the present invention and the shear wave velocity tested by SCPTU are given. Figure 7 The variation curves of the shear wave velocity estimated by the method of the present invention and the shear wave velocity of the DHT test along the depth are given. It can be seen that the shear wave velocity predicted by the method of the present invention is similar to the shear wave velocity value of the test (regardless of which test technology is used), with a small error, which verifies the accuracy of the method.

[0131] The cone tip resistance q of cohesionless soil can also be analyzed in the same soil layer t and shear wave velocity V s , get the estimated V for the same layer of soil s calculation formula to expand its scope of application.

[0132] The algorithm of steps S1-5 has been programmed to automatically realize fast and large-scale calculations.

[0133] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0134] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A shear wave velocity estimation method based on pore pressure static penetration test, characterized in that The steps include: S1. Conduct pore pressure static penetration tests on multiple boreholes on site to obtain the basic parameters of pore pressure static penetration and shear wave velocity V of each borehole tested along the depth direction. s The basic parameters of pore pressure static penetration include cone tip resistance q t , side wall friction f s , pore water pressure u2; S2. Derived parameters are interpreted based on the basic parameters of pore pressure static penetration test, wherein the derived parameters include friction ratio R f , normalized friction ratio F r , pore pressure parameter B q , Soil Classification Index I c , Normalized cone tip resistance Q tn , normalized shear wave velocity V s1 ; S3, combined with geotechnical tests and geological data, based on the cone tip resistance q t , side wall friction f s , pore water pressure u2, friction ratio R f , pore pressure parameter B q Divide soil layers based on soil classification index I c Identify soil types and determine soil types; S4, through step S3, the data tested by the same soil type are selected as the analysis object, and the data are preprocessed, including the removal of abnormal points based on the probability statistics related theory, and then three different types of fitting functions, namely exponential function, power function and linear function, are selected to analyze the cone tip resistance q of the pore pressure static penetration test. t and shear wave velocity V s Perform fitting analysis on the scatter plot to obtain the fitting formula; S5. Cone tip resistance q in basic parameters of pore pressure static penetration t and shear wave velocity V s , considering the effective overburden pressure σ′ v0 The influence of and dimensionless principle, the normalized cone tip resistance Q is obtained tn and the normalized shear wave velocity V s1 , substitute into the fitting formula in step S4, and convert the soil classification index I c Introduce and obtain the best estimate of the shear wave velocity V sE The computational expression of .

2. A shear wave velocity estimation method based on pore pressure static penetration test according to claim 1, characterized in that: The pore pressure static penetration test in step S1 adopts the seismic wave pore pressure static penetration test, and the specific method is: A set of basic parameter data of pore pressure static penetration is collected every 0.05m along the depth of each borehole, and the penetration is stopped every 1m to start seismic wave testing and collect the recovered shear wave velocity V s Parameter data.

3. The shear wave velocity estimation method based on pore pressure static penetration test according to claim 2 is characterized in that: When the seismic wave pore pressure static penetration test cannot be carried out on site, the pore pressure static penetration test in step S1 can be carried out in the following two ways: a) Perform shear wave velocity test on the pore pressure static penetration test hole at the same time, and use the shear wave velocity test hole data obtained from the shear wave velocity test as the shear wave velocity test value used in subsequent calculations; b) If the shear wave velocity test is not carried out simultaneously on the pore pressure static penetration test hole, the shear wave velocity test hole data of the borehole closest to the pore pressure static penetration test hole is selected as the shear wave velocity test hole data for subsequent calculations, and the distance between the nearest borehole and the hole is less than 0.5m.

4. A shear wave velocity estimation method based on pore pressure static penetration test according to claim 3, characterized in that: The step S2 is to interpret the derived parameters according to the basic parameters of the pore pressure static penetration test as follows: Basic parameters: cone tip resistance q t , side wall friction f s , pore water pressure u2; Derived parameter: Friction ratio R f , normalized friction ratio F r , pore pressure parameter B q , Soil Classification Index I c , Normalized cone tip resistance Q tn , normalized shear wave velocity V s1 ; Friction ratio R f The expression is: R f =f s / q t ×100% (1) Normalized friction ratio F r The expression is: F r =f s / (q t -σ v0 ) (2) In the formula, σ v0 is the overburden pressure on the soil layer; Pore ​​pressure parameter B q The expression is: B q =(u2-u0) / (q t -s v0 ) (3) Where u0 is the hydrostatic pressure; Soil Classification Index I c The calculation method is as follows: Robertson's soil classification index is denoted as I c,RW ; The soil classification index proposed by Been and Jefferies is denoted as I c,BJ ; The expressions are: In the formula, Q t =(q t -σ vo ) / σ′ vo ,σ′ v0 is the effective overburden pressure; where I c,BJ Contains pore pressure parameter B q , which can better characterize the presence or absence of clay soil; Normalized cone tip resistance Q tn The expression is: In the formula, σ′ v0 is the effective overburden pressure; n is the stress index; Specifically, n = 0.381I c +0.05(σ′ v0 / p a )-0.15≤1; where I c is the soil classification index; p a is the reference pressure, i.e. atmospheric pressure; Based on the shear wave velocity V s Test parameter data, interpret the derived parameter normalized shear wave velocity V s1 as follows: Through the above interpretation method, a derived parameter group corresponding to the cone tip resistance at every 1m interval along the depth direction can be obtained.

5. The shear wave velocity estimation method based on pore pressure static penetration test according to claim 4 is characterized in that: The specific steps of step S3 for determining the soil type are as follows: Combined with geotechnical tests and geological data, the soil layers are divided, and then each layer is divided into multiple sub-layers at intervals of 1m. The mean value of each parameter, including basic parameters and derived parameters, is calculated under each layer, which is used for the subsequent prediction of the pore pressure static penetration data points for shear wave velocity. The soil type is further clarified and verified through the soil classification map and soil classification index, and the sub-layer in each layer is normalized to the cone tip resistance Q tn and normalized friction ratio F r The data is projected onto the soil classification map, and the soil classification index I calculated based on the above sub-layers is c Identify soil types.

6. A shear wave velocity estimation method based on pore pressure static penetration test according to claim 5, characterized in that: The fitting formula obtained in step S4 is: Use the exponential function model to calculate V s1 / Q tn and I c,BJ The scatter plot is analyzed by exponential function fitting, and the specific formula is: Where a and b are fitting coefficients.

7. The shear wave velocity estimation method based on pore pressure static penetration test according to claim 6 is characterized in that: In step S5, the normalized shear wave velocity V can be obtained according to formula (8): s1 The expression is: Substituting equation (8) into equation (7) yields the best estimate of the shear wave velocity V sE Calculate the expression: Substituting equation (6) into equation (10) yields the best estimate of the shear wave velocity V sE Calculate the expression:

Images