Soil body strength modulus parameter calculation method based on standard penetration technology

Abstract

The invention discloses a soil body strength modulus parameter calculation method based on a standard penetration technology. The soil body strength modulus parameter calculation method comprises the following steps that S1, standard penetration original data of a to-be-surveyed site is obtained through geological exploration; s2, calculating a dynamic damping index of each strike of the standard penetration test; s3, calculating a standard penetration test average peak dynamic damping index considering the difference; s4, calculating a soil body strength modulus parameter; and S5, calculating the strength modulus parameters of the soil bodies at different test depths by adopting the methods shown in S1 to S4. The dynamic damping index, obtained through processing of the dynamic damping index calculation formula of the standard penetration energy, of each strike has good regressiveness, meanwhile, the dynamic damping level of the tested soil body is represented through the method, actual physical significance is given to the obtained index of the standard penetration energy, and the method has good application prospects. The defects that parameters obtained through an existing standard penetration energy test data processing method are large in discreteness and have no actual physical significance are overcome.

Description

Technical Field

[0001] The invention relates to the field of soil strength modulus parameter research, and in particular to a soil strength modulus parameter calculation method based on standard penetration technology. Background Art

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

[0003] At present, the soil layer survey depth of standard penetration technology is generally less than 20m. In order to expand the application depth of standard penetration technology, China Invention Patent Publication No. CN108375395A discloses an underground acquisition component for force and velocity signals in standard penetration test. The underground acquisition component is connected between the bottom end of the drill pipe and the standard penetrator, which can accurately test the force and acceleration directly borne by the standard penetrator, and truly reflect the interaction characteristics between the standard penetrator and the surrounding soil from the energy and mechanical level. However, there is currently no unified processing method for the force and acceleration data obtained by this standard penetration probe. The indicators obtained by data processing have problems such as poor regression, gradual decrease of indicators with increasing depth, and energy indicators exceeding the maximum energy. This limits the engineering application of the test data obtained by 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 soil strength modulus calculation method based on standard penetration technology. The method can make practical use of the data collected by the standard penetration probe through regression analysis, and the obtained soil strength parameters are close to the indoor geotechnical test results and have good regression performance.

[0005] To this end, the present invention adopts the following technical solutions: A soil strength modulus parameter calculation method based on standard penetration technique, characterized in that it comprises the following steps: 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, calculates the dynamic damping index by obtaining the product of the load and time used for traveling unit length through the data measured by 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: ;

[0006] The degree of dispersion described in S3 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 compression modulus of soil in different stress sections.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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. , .

[0011] 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.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. The method of the present invention is based on a large amount of data obtained from the standard penetration technique, and uses a semi-empirical calculation method obtained by a regression analysis method to make practical use of the data obtained from the standard penetration device.

[0013] 2. The dynamic damping index of each strike obtained by the dynamic damping index calculation formula 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 test soil, gives actual physical meaning to the index obtained by the standard penetration energy, and makes up for the shortcomings of the existing standard penetration energy test data processing method that the parameters are highly discrete and have no actual physical meaning.

[0014] 3. The method of the present invention is simple, easy, 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 used in the field of geotechnical exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure is a flow chart of a soil strength modulus calculation method in an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0017] Figure 1 The flowchart of one 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: S1, obtain the original data of standard penetration of the site to be surveyed through geological exploration: According to the geotechnical engineering investigation technical outline, first arrange the standard penetration test hole at the project site; then use the standard penetration probe to extend into the test hole, and determine the test at a certain depth according to the investigation needs. The raw data obtained from the data response under substandard hammer energy include instantaneous impact force and instantaneous acceleration. Specifically, in each hit, at time Inside, with is the time interval, collection The instantaneous impulse of the moment and instantaneous acceleration ,in, is the number of collection times, , , .

[0018] S2, calculates the dynamic damping index for each blow in the standard penetration test: Calculate the first Hit the Dynamic damping index collected : (1) In the formula, The unit is , ; The sensor measures Hit the first The instantaneous impulse, in units of ; is the time interval for collecting data, in units of ; The first Hit the The instantaneous acceleration, in units of .

[0019] S3, calculating the average peak dynamic damping index of the standard penetration test taking into account the variability, includes the following sub-steps: S31, screening the maximum value of the dynamic damping index of each hit, recording it as the peak dynamic damping index , get the initial peak dynamic damping index set; S32, calculate the average value of the peak dynamic damping index ,have: (2) in, For the The number of elements in the peak dynamic damping index set at the iteration, the initial ; S33, calculate the The dispersion degree of the dynamic damping index of the impact and the average peak dynamic damping index ,have: (3) Then, filter and remove from the peak dynamic damping index set Peak dynamic damping index.

[0020] S34, using the peak dynamic damping index set obtained in S33, repeating steps S32 and S33 to iterate until all elements in the peak dynamic damping index set correspond to all The average peak dynamic damping index at this time is used as the final average peak dynamic damping index .

[0021] S4, calculate the internal friction angle, cohesion and compression modulus of the soil: According to the final average peak dynamic damping index Calculate the soil strength modulus parameters, including the internal friction angle and cohesion of the soil and the soil compression modulus in different stress sections, as follows: Calculate the internal friction angle of soil: Internal friction angle of quick shear test Calculated by the following formula: (4) Internal friction angle of consolidation shear Calculated by the following formula: (5) Calculate soil cohesion: Cohesion in quick shear test Calculated by the following formula: (6) Cohesion of consolidation shear Calculated by the following formula: (7) Calculate the compression modulus of soil : The compression modulus of different stress sections is calculated by the following formula: (8) (9) (10) (11) S5: For soils at different test depths, methods S1 to S4 are used to solve the soil strength modulus parameters.

[0022] In one 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 engineering scope geomorphic unit of the site is a marine-alluvial coastal plain with a relatively flat terrain and an open terrain. The strata revealed within the exploration depth range are mainly artificial fill layers (quaternary Holocene artificial accumulation Qml), the first terrestrial layer (quaternary Holocene riverbed-floodplain phase deposition Q4 3 al), the first marine layer (quaternary system Holocene middle group shallow marine sedimentary Q4 2 m), the second continental layer (quaternary system lower group swamp phase sediment Q4 1 h and the Quaternary Holocene Lower Formation riverbed-floodplain facies deposits Q4 1 al), the third continental layer (the fifth group of riverbed-floodplain sediments of the Upper Pleistocene of the Quaternary System Q3 e al), the second marine layer (quaternary upper Pleistocene four groups of coastal ~ tidal zone sediments Q3 d mc), the Ⅳth continental layer (the third group of riverbed-floodplain phase deposits of the Upper Pleistocene of the Quaternary System Q3 c al), the third marine layer (quaternary upper Pleistocene second group of shallow marine to coastal sediments Q3 b m), the fifth continental layer (the Quaternary Upper Pleistocene unified formation riverbed to floodplain phase deposits Q3 a al), the rock types are mainly fill soil, silt soil and clay soil. The calculation process is as follows: S1, a standard penetration probe was inserted into the test hole, and the data response under 22 standard hammering energies was tested at a depth of 35m. The data obtained from the 22nd standard hammering are shown in Table 1. ,Right now , time interval , For the The moment of collection.

[0023] Table 1

[0024] S2, calculation of dynamic damping index Among them, the dynamic damping index collected each time in the 22nd hit The values ​​are shown in Table 2: Table 2

[0025] S3, calculate the average peak dynamic damping index of the standard penetration test taking into account the variability.

[0026] Taking the data of the 22nd strike as an example, its peak dynamic damping index is .

[0027] In the above embodiment, all peak dynamic damping indicators are shown in Table 3: Table 3

[0028] The initial average peak dynamic damping index is calculated by the following formula .

[0029] .

[0030] Then calculate the degree of dispersion between the dynamic damping index of each strike and the average dynamic damping index The calculation results are shown in Table 4.

[0031] Table 4

[0032] Culling The dynamic damping index is the 12th hit; then iterate and repeat steps S32 and S33. Finally, after the third iteration, after eliminating the 1st, 12th and 16th hit data, the discrete degree of each hit after elimination is satisfied. , at this time the average peak dynamic damping index .

[0033] S4, calculate the internal friction angle and cohesion of the soil and the compression modulus of the soil in different stress sections according to the obtained average peak dynamic damping index, as follows: Calculate the internal friction angle of soil, where: Internal friction angle of quick shear test ; Internal friction angle of consolidation quick shear .

[0034] Calculate soil cohesion, where: Cohesion in quick shear test ; Cohesion of consolidation shear .

[0035] Calculate the compression modulus of soil ,in: ; ; ; .

[0036] S5. For soils at different test depths, the S2~S4 methods are used to solve the soil cohesion and internal friction angle, and the compression modulus in different stress sections, and compared with the strength parameters obtained from indoor geotechnical tests. The comparison results are shown in Table 5.

[0037] Table 5

[0038] The blank spaces in the table are because no corresponding tests were conducted at that depth and there are no corresponding test values, so the calculated values ​​for comparison are also omitted.

[0039] It can be seen from Table 5 that the soil strength parameters calculated by the method of the present invention are similar to the parameters obtained by the indoor test, and the difference percentage is no more than 15%, which is less than the upper limit of error of 20% required by the verification calculation, verifying the rationality and reliability of the method of the present invention.

[0040] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in 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, calculates the dynamic damping index by obtaining the product of the load and time used for traveling unit length through the data measured by 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 compression modulus of soil in different stress sections.

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 dynamic damping index in S2 is calculated by the following formula: ， in, For the Hit 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. , .

6. The soil strength modulus parameter calculation method based on standard penetration technique according to claim 5 is 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