A calculation method for soil strength modulus parameters based on the standard penetration technology

Abstract

The present invention discloses a method for calculating soil strength modulus parameters based on the standard penetration technology, which includes the following steps: S1, obtaining the original standard penetration data of the site to be explored through geological exploration; S2, calculating the dynamic damping index of each blow of the standard penetration test; S3, calculating the average peak dynamic damping index of the standard penetration test considering differences; S4, calculating the soil strength modulus parameters; S5, using the method shown in S1-S4 to calculate the soil strength modulus parameters at different test depths. The dynamic damping index of each blow obtained by processing with the dynamic damping index calculation formula of the standard penetration energy of the present invention has good regression. At the same time, this method characterizes the dynamic damping level of the tested soil, endows the index obtained by the standard penetration energy with practical physical significance, and makes up for the deficiencies of the parameters obtained by the existing standard penetration energy test data processing method, which have large discreteness and no practical physical significance.

Description

Technical Field

[0001] The present invention relates to the field of research on soil strength modulus parameters, and particularly to a method for calculating soil strength modulus parameters based on standard penetration technology. Background Art

[0002] The standard penetration technology is one of the in-situ testing technologies that have been developed earlier and widely used in engineering. This technology characterizes the physical and mechanical parameters of soil by measuring the number of blows required for a standard penetrometer to penetrate a standard depth under a standard hammering energy. Since the hammering energy dissipates during the transmission along the standard penetration drill rod, when the test depth is relatively deep and the drill rod is relatively long, the energy dissipation of the standard hammering energy transmitted to the bottom standard penetrometer is relatively serious, resulting in inaccurate measurement of the number of blows characterizing the physical and mechanical properties of the soil.

[0003] Currently, the soil layer exploration depth of the application of the standard penetration technology is generally less than 20m. To expand the application depth of the standard penetration technology, Chinese Patent Publication No. CN108375395A discloses an underground acquisition component for force and velocity signals in a standard penetration test. This underground acquisition component is connected between the bottom end of the drill rod and the standard penetrometer, and can accurately measure the force and acceleration directly borne by the standard penetrometer, and truly reflect the interaction characteristics between the standard penetrometer and the surrounding soil from the aspects of energy and mechanics. However, at present, there is no unified processing method for the force and acceleration data obtained through this standard penetration probe, and there are problems such as poor regression of the indexes obtained by data processing, gradual decrease of the indexes with the increase of depth, and energy indexes exceeding the maximum energy that should be available, which limits the engineering application of the test data obtained through these standard penetration probes. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for calculating soil strength modulus based on standard penetration technology. This method can actually utilize the data collected by the standard penetration probe through regression analysis, and the obtained soil strength parameters are relatively close to the results of indoor geotechnical tests, with good regression.

[0005] To this end, the present invention adopts the following technical solutions:

[0006] A method for calculating soil strength modulus parameters based on standard penetration technology, characterized by comprising the following steps:

[0007] S1, based on the standard penetration technology, collect the data response under the standard hammering energy at the site to be surveyed, and obtain the instantaneous impact force and instantaneous acceleration directly borne by the standard penetrometer measured by the piezoelectric pressure sensor and the acceleration sensor at each blow and at a fixed time interval; S2, calculate the product of the load and the time used for traveling per unit length through the data measured in S1, and then calculate the dynamic damping index;

[0008] S3. Calculate the average peak dynamic damping index of the standard penetration test considering the differences, including the following sub-steps:

[0009] Select the maximum value of the dynamic damping index for each blow in the results obtained in S2, denote it as the peak dynamic damping index, calculate the average value of all peak dynamic damping indexes, and then calculate the corresponding degree of dispersion through the following formula ;

[0010] The degree of dispersion described in S3 Is calculated through the following formula:

[0011] ;

[0012] Wherein, Is the average value of all peak dynamic damping indexes, Is the number of times to solve the average value, Is the peak dynamic damping index of the Th blow;

[0013] If a certain degree of dispersion is greater than 100%, then eliminate the dynamic damping index of the corresponding blow number, and then calculate the degree of dispersion of the remaining peak dynamic damping indexes until all degrees of dispersion are less than or equal to 100%. Take the average peak dynamic damping index at this time as the final average peak dynamic damping index;

[0014] S4. Calculate the soil strength modulus parameters according to the final average peak dynamic damping index, including: the internal friction angle of the soil, the cohesion of the soil, and the soil compression modulus in different stress sections.

[0015] The internal friction angle of the soil described in S4 includes the internal friction angle of the soil in the quick shear test And the internal friction angle of the soil in the consolidated quick shear Are obtained according to the following two formulas:

[0016] ;

[0017] ;

[0018] Wherein, Is the final average peak dynamic damping index.

[0019] The cohesion of the soil described in S4 includes the cohesion in the quick shear test And the cohesion in the consolidated quick shear , Are obtained according to the following two formulas:

[0020] ;

[0021] ;

[0022] Among them, is the final average peak dynamic damping index.

[0023] The calculation formula for the soil compression modulus in different stress sections described in S4 is as follows:

[0024] ;

[0025] ;

[0026] ;

[0027] ;

[0028] Among them, is the compression modulus of the stress section within , is the compression modulus of the stress section within , is the compression modulus of the stress section within , is the compression modulus of the stress section within , is the final average peak dynamic damping index.

[0029] The dynamic damping index described in S2 is calculated by the following formula:

[0030] ,

[0031] Among them, is the dynamic damping index of the th hit at the th acquisition, is the instantaneous impact force of the th hit at the th time, is the instantaneous acceleration of the th hit at the th time, is the time interval for each hit, is the time within the acquisition number, , .

[0032] It also includes S5. For the soil bodies at different test depths in the site to be surveyed, the methods of S1 to S4 are used to solve the soil strength modulus parameters.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The method of the present invention is based on a large amount of data obtained by the standard penetration test technology, and uses a semi-empirical calculation method obtained by regression analysis to actually utilize the data obtained by the standard penetrometer.

[0035] 2. The dynamic damping index of each blow processed by the calculation formula of the dynamic damping index of the standard penetration energy in the present invention has good regression. At the same time, this method characterizes the dynamic damping level of the tested soil mass, gives practical physical significance to the index obtained by the standard penetration energy, and makes up for the deficiencies of the large discreteness of the parameters obtained by the existing standard penetration energy test data processing method and the lack of practical physical significance.

[0036] 3. The method of the present invention is simple, easy to implement, time-saving and efficient, and the calculated soil strength parameters are close to the results of indoor geotechnical tests, with good effects, and can be widely applied to the field of geotechnical investigation. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flow chart of the soil strength modulus calculation method in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope protected by the present invention.

[0039] Figure 1 The flow chart of an embodiment of the soil strength modulus calculation method of the present invention is shown. As shown in the figure, the method includes the following steps:

[0040] S1. Obtain the original standard penetration data of the site to be explored through geological exploration:

[0041] According to the technical outline of geotechnical engineering exploration, first arrange standard penetration test holes at the engineering site; then use a standard penetration probe to extend into the test hole, and determine the data response at a certain depth according to the exploration needs. The obtained original data includes instantaneous impact force and instantaneous acceleration. Specifically, in each blow, within the time at intervals of collect the instantaneous impact force and instantaneous acceleration at the moment of , where is the number of the collection times, , , , .

[0042] S2, calculate the dynamic damping index for each blow in the standard penetration test:

[0043] Calculate the blow of the th collected dynamic damping index through Equation (1): :

[0044] (1)

[0045] In the formula, The unit of , ; is the instantaneous impact force of the th blow measured by the sensor, and the unit is ; is the time interval of the collected data, and the unit is ; is the instantaneous acceleration of the th blow measured by the standard penetration probe, and the unit is th blow of the th, and the unit is .

[0046] S3, calculate the average peak dynamic damping index of the standard penetration test considering the differences, including the following sub-steps:

[0047] S31, screen the maximum value of the dynamic damping index for each blow, denoted as the peak dynamic damping index , and obtain the initial set of peak dynamic damping indices;

[0048] S32, calculate the average value of the peak dynamic damping indices, and there is:

[0049] (2)

[0050] Among them, is the number of elements in the set of peak dynamic damping indices at the th iteration. Initially, ;

[0051] S33, calculate the dispersion degree of the dynamic damping index of the th blow and the average peak dynamic damping index, and there is:

[0052] (3)

[0053] Then, screen and remove the peak dynamic damping indices with from the set of peak dynamic damping indices.

[0054] S34. Using the set of peak dynamic damping indexes obtained in S33, repeat steps S32 and S33 for iteration until all elements in the set of peak dynamic damping indexes correspond to all , and use the average peak dynamic damping index at this time as the final average peak dynamic damping index .

[0055] S4. Calculate the internal friction angle, cohesion and compression modulus of the soil mass:

[0056] According to the final average peak dynamic damping index calculate the strength modulus parameters of the soil mass, including the internal friction angle and cohesion of the soil mass and the compression modulus of the soil mass in different stress sections, specifically as follows:

[0057] Calculate the internal friction angle of the soil:

[0058] The internal friction angle of the quick shear test is calculated by the following formula:

[0059] (4)

[0060] The internal friction angle of the consolidated quick shear is calculated by the following formula:

[0061] (5)

[0062] Calculate the cohesion of the soil:

[0063] The cohesion of the quick shear test is calculated by the following formula:

[0064] (6)

[0065] The cohesion of the consolidated quick shear is calculated by the following formula:

[0066] (7)

[0067] Calculate the compression modulus of the soil :

[0068] The compression moduli in different stress sections are calculated by the following formulas respectively:

[0069] (8)

[0070] (9)

[0071] (10)

[0072] (11)

[0073] S5. For soils with different test depths, the methods of S1 to S4 are used to solve the soil strength modulus parameters.

[0074] In an embodiment of the present invention, the method of the present invention is used to calculate the soil strength modulus parameters of a certain engineering site. The geomorphic unit of the engineering scope of this site is the marine - alluvial coastal plain, with relatively flat terrain and open area. The strata revealed within the exploration depth are mainly artificial fill layer (Quaternary Holocene artificial accumulation Qml), the first alluvial layer (Quaternary Holocene riverbed - floodplain facies sediment Q 4 3 al), the first marine layer (Quaternary Holocene middle group shallow - marine facies sediment Q 4 2 m), the second alluvial layer (Quaternary Holocene lower group swamp facies sediment Q 4 1 h and Quaternary Holocene lower group riverbed - floodplain facies sediment Q 4 1 al), the third alluvial layer (Quaternary Upper Pleistocene fifth group riverbed - floodplain facies sediment Q 3 e al), the second marine layer (Quaternary Upper Pleistocene fourth group coastal - tidal zone facies sediment Q 3 d mc), the fourth alluvial layer (Quaternary Upper Pleistocene third group riverbed - floodplain facies sediment Q 3 c al), the third marine layer (Quaternary Upper Pleistocene second group shallow - marine - coastal facies sediment Q 3 b m), the fifth alluvial layer (Quaternary Upper Pleistocene first group riverbed - floodplain facies sediment Q 3 a al). The lithology is mainly fill, silty clay, and clay. The calculation process is as follows:

[0075] S1. The standard penetration probe is inserted into the test hole, and the data responses under 22 standard hammer - blow energies are tested at a depth of 35 m. The data obtained from the 22nd standard hammer - blow are shown in Table 1. A total of , that is , time interval , is the moment of the th acquisition.

[0076] Table 1

[0077]

[0078] S2. Calculate the dynamic damping index Among them, the dynamic damping index collected each time at the 22nd blow has values as shown in Table 2:

[0079] Table 2

[0080]

[0081] S3. Calculate the average peak dynamic damping index of the standard penetration test considering the differences.

[0082] Taking the data of the 22nd blow as an example, its peak dynamic damping index is .

[0083] In the above embodiment, all the peak dynamic damping indices are as shown in Table 3:

[0084] Table 3

[0085]

[0086] Calculate the initial average peak dynamic damping index through the following formula .

[0087] .

[0088] Then calculate the dispersion degree of the dynamic damping index of each blow and the average dynamic damping index , and the calculation results are shown in Table 4.

[0089] Table 4

[0090]

[0091] Reject the dynamic damping index of, that is, the 12th blow; then perform iteration, repeat steps S32 and S33. Finally, after experiencing the third iteration and rejecting the data of the 1st blow, the 12th blow and the 16th blow, the dispersion degree of each blow after rejection satisfies , and at this time the average peak dynamic damping index .

[0092] S4. Calculate the internal friction angle and cohesion of the soil mass and the soil compression modulus in different stress sections according to the obtained average peak dynamic damping index, specifically as follows:

[0093] Calculate the internal friction angle of the soil mass, where:

[0094] The internal friction angle of the quick shear test ; the internal friction angle of the consolidated quick shear .

[0095] Calculate the cohesion of the soil mass, where:

[0096] The cohesion of the quick shear test ; Cohesion of consolidated quick shear .

[0097] Calculate the compression modulus of the soil mass , where:

[0098] ;

[0099] ;

[0100] ;

[0101] .

[0102] S5. For the soil masses at different test depths, the methods of S2 - S4 are used to solve the cohesion and internal friction angle of the soil mass, and the compression modulus under different stress sections, and compare them with the strength parameters obtained from indoor geotechnical tests. The comparison results are shown in Table 5.

[0103] Table 5

[0104]

[0105] The blanks in the table are due to the fact that no corresponding tests were carried out at this depth and there are no corresponding test values, so the calculated values for comparison with them are also omitted.

[0106] As can be seen from Table 5, the soil strength parameters calculated by the method of the present invention are similar to the parameters obtained from indoor tests, and the difference percentage is not greater than 15%, which is less than the error upper limit of 20% required for checking calculations, verifying the rationality and reliability of the method of the present invention.

[0107] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A soil strength modulus parameter calculation method based on standard penetration technique, characterized in that: The following steps are involved: S1, based on the standard penetration technology, collects data response under standard hammer energy at the site to be surveyed, and obtains the instantaneous impact force and instantaneous acceleration directly borne by the standard penetrator measured by the piezoelectric pressure sensor and acceleration sensor at each impact and fixed time interval; S2, calculate the dynamic damping index by multiplying the load and time used per unit length of travel using the data measured in S1; S3, calculating the average peak dynamic damping index of the standard penetration test taking into account the variability, includes the following sub-steps: The maximum value of the dynamic damping index of each strike in the results obtained by screening S2 is recorded as the peak dynamic damping index. The average value of all peak dynamic damping indexes is calculated, and then the corresponding discrete degree is calculated by the following formula: ; ； in, is the average value of all peak dynamic damping indicators, To solve for the average, For the Peak dynamic damping index of impact; If a certain discrete degree is greater than 100%, the dynamic damping index of the corresponding number of hits is eliminated, and then the discrete degrees of the remaining peak dynamic damping indexes are calculated until all discrete degrees are less than or equal to 100%, and the average peak dynamic damping index at this time is taken as the final average peak dynamic damping index; S4, calculating soil strength modulus parameters according to the final average peak dynamic damping index, including: internal friction angle of soil, cohesion of soil and soil compression modulus in different stress sections; The dynamic damping index in S2 is calculated by the following formula: ， in, For the Hit the first The dynamic damping index collected for the first time, For the Hit the The instantaneous impulse, For the Hit the The instantaneous acceleration, is the time interval between each hit, For time The number of acquisition times within. , .

2. The soil strength modulus parameter calculation method based on standard penetration technique according to claim 1 is characterized in that: The internal friction angle of the soil described in S4 includes the internal friction angle of the soil in the quick shear test and the internal friction angle of soil in consolidation shear According to the following two formulas: ； ； in, is the final average peak dynamic damping index.

3. The soil strength modulus parameter calculation method based on standard penetration technique according to claim 1 is characterized in that: The cohesion of soil mentioned in S4 includes the cohesion of quick shear test and cohesion of consolidation shear , according to the following two formulas: ； ； in, is the final average peak dynamic damping index.

4. The soil strength modulus parameter calculation method based on standard penetration technique according to claim 1 is characterized in that: The calculation formula for the soil compression modulus in different stress sections described in S4 is as follows: ； ； ； ； in, The stress section is The compression modulus inside The stress section is , The stress section is , The stress section is , is the final average peak dynamic damping index.

5. The soil strength modulus parameter calculation method based on standard penetration technique according to any one of claims 1 to 4, characterized in that: The method further comprises S5, wherein for soil bodies at different test depths in the site to be surveyed, the soil strength modulus parameters are solved by using the methods of S1 to S4.

Images