A method for calculating compaction degree of cement-soil compaction pile based on resistivity inversion

Abstract

This invention discloses a method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion, relating to the field of engineering application technology. The method includes obtaining the resistivity, cement content, moisture content, age, and dry density of multiple cement-soil compaction piles; determining the resistivity calculation formula for cement-soil compaction piles using data fitting and theoretical calculations; obtaining the maximum dry density of multiple cement-soil compaction piles; determining the compaction degree calculation formula for cement-soil compaction piles based on the dry density and maximum dry density; and determining the comprehensive relationship between the compaction degree of cement-soil compaction piles and their resistivity, moisture content, age, and cement content based on the resistivity calculation formula and the compaction degree calculation formula. In summary, this method has advantages such as simple operation, wide applicability, short working time, high reliability of the obtained compaction degree data, and avoidance of damage to the pile body.

Description

Technical Field

[0001] This invention relates to the field of engineering application technology, specifically to a method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion. Background Technology

[0002] For a long time, the most important testing indicator for the quality control of cement-soil compaction piles has been the compaction degree of the pile body. Currently, the main method for testing the compaction degree of the pile body is to use the ring cutter method to measure the dry density of the soil sample, and then combine it with the compaction test to measure the maximum dry density of the soil sample, and finally obtain the compaction degree.

[0003] However, the following problems exist when using the ring cutter method to measure compaction degree in practice: First, when there is relatively loose coarse aggregate in the pile body, the compaction degree obtained by the ring cutter method has a large error; second, the ring cutter method for testing compaction degree is cumbersome, labor-intensive, and time-consuming, resulting in low efficiency; finally, the ring cutter method will damage the structure of the cement-soil compacted pile to some extent when sampling the pile body. Therefore, it is particularly important to adopt a non-destructive and rapid method for testing compaction degree. Summary of the Invention

[0004] To address the problems of traditional ring sampler sampling methods, such as long testing time, difficulty in representing the compaction degree of the entire pile, slight damage to the pile, and unsuitability for testing the compaction degree of piles with large aggregates, this invention provides a method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion, comprising the following steps:

[0005] The resistivity, cement content, moisture content, age, and dry density of multiple cement-soil compaction piles were obtained. Using data fitting and theoretical calculations, the formula for calculating the resistivity of cement-soil compaction piles was determined.

[0006] Obtain the maximum dry density of multiple cement-soil compaction piles, and determine the compaction degree calculation formula for cement-soil compaction piles based on the dry density of the piles and the maximum dry density.

[0007] Based on the formulas for calculating the resistivity and compaction degree of cement-soil compaction piles, the comprehensive relationship between the compaction degree of cement-soil compaction piles and its resistivity, moisture content, age, and cement content is determined.

[0008] The resistivity and moisture content of the cement-soil compaction piles were measured, and the resistivity and moisture content of the cement-soil compaction piles were imported into the comprehensive relationship formula between the compaction degree of the cement-soil compaction piles and their resistivity, moisture content, age and cement content to calculate the compaction degree of the cement-soil compaction piles.

[0009] In the formula, ρ is the resistivity; a wω represents the cement content of the pile body on site; ω represents the moisture content of the on-site sample; t represents the age of the pile body; ρ d ρ is the dry density obtained from the on-site sampling; k is the degree of compaction; max Let be the maximum dry density of the pile; a, x, and y are constants.

[0010] Furthermore, the acquisition of the resistivity of the cement-soil compaction pile specifically includes:

[0011] Level and clean the top of the pile;

[0012] The Wenner four-pole method was used to lay out the poles perpendicularly to each other on the top surface of the pile.

[0013] The electrode rods are hammered into the pile body and connected to the soil resistivity meter. The spacing between the electrode rods is input into the resistivity meter, and the resistivity of the pile body is obtained through the resistivity meter.

[0014] Furthermore, the cement content and age of the cement-soil compaction pile are obtained from the cement-soil compaction pile data, wherein the cement content of the cement-soil compaction pile ranges from 6% to 12%, and the age range of the cement-soil compaction pile ranges from 1 day to 28 days.

[0015] Furthermore, obtaining the moisture content of the cement-soil compaction pile specifically includes:

[0016] Sampling of the pile body at the sampling site;

[0017] The moisture content of the pile body is obtained by drying it for 10-12 hours using the drying method and dividing the mass reduction after drying by the mass of the dried sample.

[0018] Furthermore, obtaining the moisture content of the cement-soil compaction pile specifically includes:

[0019] The original structural specimens taken from the target pile were weighed;

[0020] The original structural sample was sealed with paraffin, and the mass of the sealed sample was measured. Then, it was placed in an electronic densitometer to measure its mass in water.

[0021] The dry density of the undisturbed sample is calculated using the following formula:

[0022]

[0023] In the formula: ρ d ρ is the dry density of the soil; m is the mass of the specimen; m1 is the mass of the wax-sealed specimen; m2 is the mass of the wax-sealed specimen in water; ρ wt ρ is the density of pure water at t℃. n ω represents the density of paraffin wax; ω represents the water content.

[0024] Furthermore, the resistivity calculation formula for cement-soil compaction piles is determined by using data fitting and theoretical calculation. Specifically, it includes:

[0025] Based on the resistivity, cement content, moisture content, age, and dry density of multiple cement-soil compaction piles, the relationship between the resistivity of cement-soil compaction piles and cement content, moisture content, age, and dry density was determined by data fitting. Among them, the resistivity of cement-soil compaction piles increased exponentially with respect to cement content and age, while the resistivity of cement-soil compaction piles increased exponentially with respect to moisture content and dry density.

[0026] Based on the relationship between the resistivity of cement-soil compaction piles and cement content, moisture content, curing time, and dry density, a formula for calculating the resistivity of cement-soil compaction piles is determined through theoretical calculations.

[0027] Compared with existing technologies, the present invention provides a method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion, which has the following advantages:

[0028] The method of this invention, when measuring the compaction degree of cement-soil compaction piles, only requires the time to drive electrodes into the pile body at preset positions, install temperature and humidity sensors at preset points, and debug the equipment. The entire process takes only 20-30 minutes. Furthermore, the implementation only requires the deployment of electrodes and sensors, which is based on non-destructive testing. Compared with the traditional sampling process, this method saves testing costs and improves work efficiency. At the same time, the compaction degree predicted on-site by this method is not much different from the compaction degree obtained by indoor test methods, with the overall average error controlled within 5.5%, making it feasible in practical engineering. In summary, compared with the ring cutter method for testing the compaction degree of piles, this invention is simple to operate, widely applicable, has a short working time, obtains highly reliable compaction degree data, and avoids damage to the pile body. Attached Figure Description

[0029] Figure 1 A schematic diagram illustrating the principle of a method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion, provided by this invention.

[0030] Figure 2 A front view of the Winner quadrupole method layout provided in an embodiment of the present invention;

[0031] Figure 3 This is a front view of the temperature and humidity sensor layout provided in an embodiment of the present invention;

[0032] Figure 4 This is a top view showing the layout of resistivity and moisture content measuring points provided in an embodiment of the present invention.

[0033] Figure 5 This is a comparison chart of the compaction degree measured by the method of the present invention and the actual compaction degree. Detailed Implementation

[0034] The following is in conjunction with the appendix Figure 1-5 The following describes specific embodiments of the present invention in further detail. These embodiments are merely for illustrating the technical solutions of the present invention more clearly and should not be construed as limiting the scope of protection of the present invention.

[0035] Example 1: Combination Figure 1 This invention proposes a method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion, including the following steps: 1) obtaining the field resistivity and physical property index of the pile body sample, and establishing the basic relationship affecting resistivity; 2) data analysis and processing; 3) testing the field resistivity and moisture content and calculating the compaction degree of the cement-soil compaction pile body.

[0036] 1) Obtain the field resistivity and physical properties of the pile samples, and establish the basic relationships affecting resistivity.

[0037] By combining field pile resistivity tests with physical parameters such as cement content, moisture content, age, and dry density, the relationship between pile resistivity and these parameters was established. Resistivity was measured using the Winner four-electrode method, as shown in the attached figure. Figure 2 With appendix Figure 4 Resistivity was measured twice on the upper part of the pile body at equal intervals, with the test sites perpendicular to each other. The resistivity was the average of the two tests. The cement content of the pile body ranged from 6% to 12%. The age of the pile body ranged from 1 day to 28 days. The moisture content was obtained by drying the pile body samples on-site using a drying method (temperature set at 100℃-105℃) for 10-12 hours. To determine the dry density of the original pile body sample, the dry density was measured using a wax sealing method after sampling the pile body on-site. Data fitting revealed that the resistivity of the pile body increased exponentially with its cement content and age, while it increased power-lawly with its moisture content and dry density.

[0038] 2) Data Analysis and Processing

[0039] Extensive experiments were conducted to obtain the comprehensive relationship between the in-situ resistivity of the pile and its cement content, moisture content, age, and dry density. Then, a formula was derived through theoretical calculations.

[0040]

[0041] The maximum dry density of the pile was obtained by conducting a compaction test after on-site sampling, using the following formula:

[0042]

[0043] Substituting into the above formula, we obtain the comprehensive relationship between the compaction degree of the pile body on site and its resistivity, moisture content, age, and cement content, as shown in the following formula:

[0044]

[0045] Where: ρ is the resistivity (Ω·m);

[0046] a w The cement content (%) of the pile body on site;

[0047] ω represents the moisture content (%) of the on-site sample;

[0048] t represents the age (d) of the pile.

[0049] ρ d The dry density (g / cm³) of the sample taken on site. 3 );

[0050] k represents the degree of compaction;

[0051] ρ max The maximum dry density of the pile (g / cm³) 3 );

[0052] a, x, and y are constants.

[0053] 3) On-site testing of resistivity and moisture content, and calculation of pile compaction degree.

[0054] See appendix Figure 2-4 According to the set locations and methods of the electrodes and temperature and humidity sensors, the resistivity of the pile body was tested on site using the Wenner quadrupole method, and its moisture content was tested using temperature and humidity sensors. The electrodes and temperature and humidity sensor probes were inserted into the soil to a length of 2 / 3, ensuring good contact. Then, the resistivity and moisture content measured on site were imported into the above-mentioned formula for compaction to obtain the compaction degree of the pile body.

[0055] Example 2: This example is a specific application of Example 1; the specific steps of this example are as follows:

[0056] Step 1: Select 20 target piles at the project site and conduct on-site resistivity testing using the Wenner four-electrode method. The project site described in this example is Haiyuan County, Zhongwei City, Ningxia Hui Autonomous Region. The specific method for resistivity testing is as follows: Level and clean the top of the piles, and then... Figure 4 The installation method involves using the Wenner four-electrode method to install electrodes perpendicularly to each other on the top surface of the pile. The electrodes are hammered into the pile body 10cm (approximately 2 / 3 of the total length of the electrode rod), connected to the soil resistivity meter, and the spacing between the electrodes is input into the resistivity meter. Finally, the resistivity of the pile body is obtained through the resistivity meter.

[0057] Step 2: Randomly select two samples with a mass greater than 10g from each pile body on site, place them in an oven at a temperature of 100℃-105℃, and dry them for 10h-12h. Divide the mass reduction after drying by the mass of the dried sample to obtain the moisture content of the pile body.

[0058] Step 3: Weigh the undisturbed structural sample taken from the target pile, then seal it with paraffin wax. After sealing, weigh the wax-sealed sample and then weigh it in water using an electronic density meter. Calculate the dry density of the undisturbed sample using the following formula:

[0059]

[0060] In the formula: ρ d The dry density of the soil is calculated to the nearest 0.01 g / cm³. 3 ;

[0061] m is the mass of the specimen (g);

[0062] Mass of m1 wax-sealed specimen (g);

[0063] m2 wax-sealed specimen mass in water (g);

[0064] ρ wt The density of pure water at t℃ is accurate to 0.001 g / cm3.

[0065] ρ n The density of paraffin wax should be measured beforehand, accurate to 0.01 g / cm³; generally, 0.92 g / cm³ can be used.

[0066] ω represents the moisture content (%).

[0067] Step 3: Based on the resistivity measured on-site, the moisture content and dry density obtained from indoor tests, and the cement content and age obtained from the on-site pile data, the relationship between resistivity and each individual variable is obtained. Then, data analysis is performed to obtain the comprehensive relationship between resistivity and cement content, moisture content, age, and dry density: The information on the 20 sets of samples obtained in this embodiment is shown in Table 1:

[0068] Table 1. Experimental Data of Pile Structures in Haiyuan County

[0069]

[0070]

[0071] Step 3: Select target piles at the engineering site for sampling and send them to the laboratory for compaction tests to obtain the maximum dry density and optimum moisture content of the pile body. The specific steps for obtaining the maximum dry density in this embodiment are as follows: After passing the on-site sample through a 20mm sieve, divide it into five portions, each approximately 2.5kg, and prepare samples with moisture contents of 8%, 10%, 12%, 14%, and 16% respectively. Then, use heavy compaction. After compaction and weighing, randomly select two samples from the sample body and use the drying method to measure their moisture content. Substitute the moisture content and wet density into the following formula to calculate the dry density:

[0072]

[0073] In the formula: ρ d For dry density, calculate to 0.01 g / cm³. 3 ;

[0074] ρ0 is the wet density (g / cm³) 3 );

[0075] ω represents the moisture content (%).

[0076] Then, plot the curve of dry density versus moisture content on a rectangular coordinate system. The peak points of the curve correspond to the maximum dry density and the optimum moisture content. In this example, the maximum dry density is 1.91 g / cm³. 3 .

[0077] Step 4: Substitute the maximum dry density into the formula: The comprehensive relationship between compaction degree and cement content, moisture content, age, and dry density is obtained:

[0078]

[0079] Step 5: Import the resistivity and moisture content obtained on-site by the Wenner quadrupole method and temperature and humidity sensor into the comprehensive calculation formula to obtain the compaction degree that can be quickly and non-destructively tested on-site using this method.

[0080] Combining Examples 1 and 2, a comparison between this method and traditional methods reveals that traditional compaction methods first require preparing samples with different moisture contents for compaction tests to obtain the maximum dry density. Secondly, they require sampling with a ring cutter, drying, and weighing the samples to obtain their dry density. Finally, the compaction degree of the pile body is obtained. Excluding the time lost during sample transportation, the entire process takes approximately 2-3 days, resulting in high costs for sampling, transportation, and testing, and low work efficiency. The method of this invention is based on the coupling inversion of resistivity and moisture content to determine the compaction degree of cement-soil compaction piles. In field testing, only the time required to drive electrodes into the pile body at preset positions, install temperature and humidity sensors at preset points, and adjust the equipment is needed; the entire process takes only 20-30 minutes. This method only requires the deployment of electrodes and sensors, and is based on non-destructive testing. Compared to traditional sampling processes, this method saves testing costs and improves work efficiency.

[0081] See appendix Figure 5 The comparative analysis between the compaction degree predicted by this method in the field and the compaction degree obtained by the corresponding indoor test shows that the compaction degree test method of cement-soil compaction pile based on the coupling inversion of resistivity and moisture content is not much different from the compaction degree obtained by the indoor test method. The overall average error is controlled within 5.5%, which is feasible in actual engineering.

[0082] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion, characterized in that, Includes the following steps: Obtain the resistivity, cement content, moisture content, age, and dry density of multiple cement-soil compaction piles; Based on the relationship between the resistivity of cement-soil compaction piles and cement content, moisture content, age, and dry density, a formula for calculating the resistivity of cement-soil compaction piles is determined using data fitting and theoretical calculations. The formula for calculating the resistivity of cement-soil compaction piles is as follows: In the formula, ρ is the resistivity; a w ω represents the cement content of the pile body on site; ω represents the moisture content of the on-site sample; t represents the age of the pile body; ρ d Let be the dry density of the on-site sample; a, x, and y are constants. The maximum dry density of multiple cement-soil compaction piles is obtained. Based on the dry density and maximum dry density of the cement-soil compaction piles, the compaction degree calculation formula for the cement-soil compaction piles is determined. The compaction degree calculation formula for the cement-soil compaction piles is as follows: In the formula, k is the degree of compaction; ρ max The maximum dry density of the pile body; Based on the formulas for calculating the resistivity and compaction degree of cement-soil compaction piles, a comprehensive relationship is determined between the compaction degree of cement-soil compaction piles and their resistivity, moisture content, age, and cement content. This comprehensive relationship is as follows: The resistivity and moisture content of the cement-soil compaction piles were measured, and the resistivity and moisture content of the cement-soil compaction piles were imported into the comprehensive relationship formula between the compaction degree of the cement-soil compaction piles and its resistivity, moisture content, age and cement content to calculate the compaction degree of the cement-soil compaction piles.

2. The method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion as described in claim 1, characterized in that, The acquisition of the resistivity of the cement-soil compaction pile specifically includes: Level and clean the top of the pile; The Wenner four-pole method was used to lay out the poles perpendicularly to each other on the top surface of the pile. The electrode rods are hammered into the pile body and connected to the soil resistivity meter. The spacing between the electrode rods is input into the resistivity meter, and the resistivity of the pile body is obtained through the resistivity meter.

3. The method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion as described in claim 1, characterized in that, The cement content and age of the cement-soil compaction piles are obtained from the cement-soil compaction pile data, wherein the cement content range of the cement-soil compaction piles is 6%-12%, and the age range of the cement-soil compaction piles is 1d-28d.

4. The method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion as described in claim 1, characterized in that, The method for obtaining the moisture content of the cement-soil compaction piles specifically includes: Sampling of the pile body at the sampling site; The moisture content of the pile body is obtained by drying it for 10-12 hours using the drying method and dividing the mass reduction after drying by the mass of the dried sample.

5. The method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion as described in claim 1, characterized in that, The method for obtaining the moisture content of the cement-soil compaction piles specifically includes: The original structural specimens taken from the target pile were weighed; The original structural sample was sealed with paraffin, and the mass of the sealed sample was measured. Then, it was placed in an electronic densitometer to measure its mass in water. The dry density of the undisturbed sample is calculated using the following formula: In the formula: ρ d ρ is the dry density of the soil; m is the mass of the specimen; m1 is the mass of the wax-sealed specimen; m2 is the mass of the wax-sealed specimen in water; ρ wt ρ is the density of pure water at t℃. n ω represents the density of paraffin wax; ω represents the water content.

6. The method for calculating the compaction degree of cement-soil compaction piles based on resistivity inversion as described in claim 1, characterized in that, The resistivity calculation formula for cement-soil compaction piles is determined by using data fitting and theoretical calculation. Specifically, it includes: Based on the resistivity, cement content, moisture content, age, and dry density of multiple cement-soil compaction piles, the relationship between the resistivity of cement-soil compaction piles and cement content, moisture content, age, and dry density was determined by data fitting. Among them, the resistivity of cement-soil compaction piles increased exponentially with respect to cement content and age, while the resistivity of cement-soil compaction piles increased exponentially with respect to moisture content and dry density. Based on the relationship between the resistivity of cement-soil compaction piles and cement content, moisture content, curing time, and dry density, a formula for calculating the resistivity of cement-soil compaction piles is determined through theoretical calculations.

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