In-situ test method for compaction performance of boulder till

Abstract

The present invention discloses an in-situ test method for the compaction performance of moraine soil containing boulders, and the steps are as follows: A. Sampling and calculating the gravel content: taking soil samples on-site from the compacted subgrade of moraine soil containing boulder components; B. Calculating the dry density of the soil and gravel parts: calculating the dry density of the soil and gravel; C. Measuring the resistivity of the soil part indoors: using a sample press method to prepare cylindrical compacted samples of moraine soil with different dry densities; D. Calculating the relationship between the dry density and resistivity of the soil part; E. Measuring the resistivity of the compacted subgrade of moraine soil on-site: using the four-electrode method to conduct on-site resistivity measurement on the compacted subgrade of moraine soil; F. Calculating the overall dry density of the on-site soil material; G. Measuring the maximum dry density of the on-site soil material; H. Detecting the compaction degree of the moraine soil subgrade. The method is easy to implement and simple to operate, solving the technical problems and difficulties of data distortion and low efficiency in obtaining the dry density and compaction degree of subgrade materials containing boulder particles by the existing methods.

Description

Technical Field

[0001] The present invention belongs to the technical field of in-situ testing in geotechnical engineering, and more particularly relates to an in-situ testing method for the compaction performance of moraine soil containing boulders, which is applicable to tests for determining the in-situ compaction performance of soil masses. Background Art

[0002] Moraine soil is a kind of soil formed by the final deposition due to the erosion and transportation of glaciers, and is distributed in certain areas in the high mountains, extremely high mountains and surrounding areas in southwestern China. From the perspective of engineering classification, moraine soil generally belongs to coarse-grained soil, boulder soil or gravel soil. The particle composition and components of moraine soil vary in different regions, with relatively large changes, and there are certain differences between its gradation and compression properties and the requirements of engineering fillers. Therefore, it is rarely used in filling projects when conditions permit. In recent years, with the rapid development of transportation engineering in China, some under-construction and planned highways and high-speed railways have attempted to use this special soil as subgrade filler. For example, there are a large number of filling projects on the China-Pakistan Highway and the Leya Expressway, with a great demand for filling soil materials. In this case, the principle of "adjusting measures to local conditions and making the best use of local materials" is usually adopted in engineering to solve the problem nearby. Therefore, the moraine soil widely distributed near the China-Pakistan Highway and the Leya Expressway has received attention. In order to be able to use moraine soil to fill subgrades, it is necessary to study its road-use characteristics and compaction performance, clarify its road-use properties, and further study the settlement law after filling the subgrade with moraine soil.

[0003] As a regional special soil, the macroscopic characteristics of moraine soil are no sorting, no orientation, no rounding, and no bedding. The fine and microscopic characteristics can be summarized as "the inhomogeneity and diversity of particle composition, the duality of mesoscopic fabric, the disorder and cementation of microscopic structure". The typical engineering characteristic is that the fine-grained glacial deposits contain a wide range of gravel components, and the gravel content varies greatly. Such gradation composition and structural characteristics pose challenges to the accurate evaluation of its compaction performance. At present, the evaluation of the compaction performance of soil is mostly reflected by the degree of compaction. The tests for the degree of compaction mainly include laboratory tests and field tests. The "Technical Specifications for Highway Subgrade Construction" (JTG F10-2006) stipulates that during the construction of the subgrade, the degree of compaction should be inspected for each compacted layer. When using laboratory tests, it is necessary to take samples and conduct tests on each layer of compacted soil, but this is not suitable for moraine soil containing gravel, because the spatial variability of the gravel content is large. In order to obtain the degree of compaction more accurately, it is necessary to increase the number of test samples, which results in low test efficiency and large discreteness of test results. In addition, most of the existing test instruments and methods for the degree of compaction of soil are for fine-grained soil and are not suitable for moraine soil containing gravel components. On the other hand, there are also many drawbacks in the current in-situ test methods for the compaction performance of soil, such as the nuclear densitometer measurement method and the field sand replacement method, when testing the compaction performance of moraine soil. The nuclear densitometer may cause radiation damage to the human body and is not conducive to long-term use. The basic principle of the sand replacement method is to use clean, dry and uniform sand with a particle size of 0.3-0.6mm or 0.25-0.5mm to freely fall from a certain height into the test hole, measure the volume of the test hole according to the principle of constant unit weight, and calculate the measured dry density of the sample based on the water content of the aggregate. However, when the test hole is near the gravel, it will cause the size of the test hole to be non-standard and the test result error to be large. Although there are currently in-situ test methods for the degree of compaction of the foundation (such as patent application numbers: CN202210257108.3; CN202222052828.4), these methods are only applicable to foundation soil layers without gravel or without large gravels. When testing moraine soil with a high content of gravel, there will still be problems such as low efficiency, long time consumption, complex operation, and large result error.

[0004] To sum up, it can be found that the accurate test of the compaction performance of moraine soil can provide subgrade parameters of compacted soil for engineers, and can also provide necessary technical support for evaluating the engineering performance of the subgrade and predicting post-construction settlement. Due to the large variation in the content of gravel components in moraine soil, the current test methods for the compaction performance of soil are not applicable. In response to this problem, there is currently no solution for testing the degree of compaction of moraine soil subgrade. Summary of the Invention

[0005] The purpose of the present invention is to provide an in-situ test method for the dry density and compaction of moraine soil filling roadbed, which is easy to implement and simple to operate, and solves the technical problems and difficulties of data distortion and low efficiency when obtaining the dry density and compaction of roadbed materials containing giant gravel particles in the existing method. The method has a clear principle and low cost, and can effectively eliminate the large error generated by the existing in-situ compaction determination method of foundation when it is used for moraine soil, and realize the on-site rapid and direct determination of the compaction of moraine soil pressure roadbed.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical measures:

[0007] An in-situ testing method for compaction performance of moraine soil containing boulders, the steps of which are:

[0008] 1. Sampling and calculation of gravel content: Take a bulk soil sample of mass m on site at the moraine compacted roadbed containing giant gravel components. According to the "Engineering Classification Standard for Soil" (GB / T 50145-2007), the bulk soil sample material is divided into a soil part S with a particle size of ≤2mm and a gravel part G with a particle size of >2mm by sieving. Each time the soil sample is sieved, 500g of the soil sample should be weighed, and the sample mass should be measured accurately to 1g. Finally, the total mass of the soil part of the bulk soil sample is m S and the total mass of the gravel part m G To ensure the accuracy of the screening test, after the screening is completed, the formula Δm=|m-(m G+ m S )|Calculate the difference between the total mass of the samples above and below the sieve after screening and the total mass of the samples before screening, Δm. This value should be less than 1% of the total mass of the soil sample. The gravel content P of the compacted soil of the roadbed is calculated by the formula P = m G / (m G+ m S )×100%.

[0009] 2. Calculate the dry density of the soil and gravel parts: Calculate the dry density of the soil part S and the gravel part G respectively. For the soil part S, test its density ρ according to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019) Si With moisture content w Si , and by the formula Calculate the dry density ρ of the soil portion S dSi , three parallel tests should be carried out on the same soil sample, and the average value of the three parallel test results is taken as the dry state density of the soil sample, that is, Where: Si The density and ρ are obtained from a single parallel test. dSi is the dry density obtained from a single parallel test, w Si The moisture content and ρ obtained from a single parallel testdS is the dry density of the soil part S. For the gravel part G, it is dried in an oven (ordinary) with the temperature controlled at 110 °C for 12 hours. The density of the dried specimen is tested according to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019), and the obtained result is the dry density ρ of the gravel part G dG .

[0010] 3. Measuring the resistivity of the soil part indoors: According to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019), use a sample press to prepare 5 cylindrical moraine soil compaction samples with different dry densities (height 100 mm, diameter 50 mm). The mass m1 of the wet soil required to prepare the first compaction sample is determined according to the formula m1=(1 + 0.01w s )ρ dS V, and the masses m i , i = 2, 3, 4, 5 of the wet soil for the remaining four compaction samples are obtained by increasing the mass of the wet soil of the first compaction sample m0 by 2% incrementally four times; where: m i is the mass of the wet soil of the i-th compaction sample, w S is the water content of the wet soil, ρ dS is the dry density of the soil sample, and V is the volume of the sample press. When preparing the sample, pour the wet soil into the sample press (ordinary), and take out the soil sample after pressing it tightly with the piston. The dry density of the compaction sample corresponding to different wet soil masses can be calculated by the formula ρ dSi =m i / (1 + 0.01w s )V, i = 1, 2, 3, 4, 5; where: ρ dSi is the dry density of the i-th compaction sample, m i is the mass of the wet soil of the i-th compaction sample, w S is the water content of the wet soil, and V is the volume of the sample press. Measure the resistivity of the five prepared samples 9 with different dry densities respectively. Place the sample in a hollow cylindrical mold tube with an inner diameter of 50 mm, an outer diameter of 52 mm, and an internal height of 100 mm. The upper and lower parts of the mold tube are respectively equipped with a top cover and a bottom cover made of the same material, with a diameter of 60 mm and a thickness of 5 mm and copper bolts. Place disk-shaped top copper electrodes and disk-shaped bottom copper electrodes with a diameter of 50 mm and a thickness of 2 mm on the top and bottom of the sample, and use the top cover and bottom cover to seal the sample. The copper bolts of the top seat and the copper bolts of the bottom seat are connected to an external power supply (alternating current with a constant frequency of 60 Hz and an applied voltage of 35 V) through wires, and are respectively in contact with the disk-shaped top copper electrode and the disk-shaped bottom copper electrode inside the mold tube. Insert upper copper rods and into the cylindrical sample, and the vertical distance between the two copper rods and is the same as the distances from the upper copper rods and to the bottom and top respectively (both are 33.3 mm). Use a voltmeter 6 to measure the resistivity of the five samples with different dry densities (ρ dSi, the potential difference ΔV between the copper rod and the samples (i = 1 - 5) was measured respectively i , and then according to the formula , the resistivity (ρ i , i = 1 - 5) of the samples was calculated: In the formula, S is the electrode area; L is the electrode spacing; I is the current intensity, and ΔV i is the potential difference.

[0011] 4. Calculate the relationship between the dry density of the soil part and the resistivity: According to the dry densities (ρ dSi , i = 1 - 5) and resistivities (ρ i , i = 1 - 5) of the five compacted samples measured in Step 2 and Step 3, draw the relationship curve of dry density and resistivity ρ = f(ρ dS ), and fit it in the form of an inverse proportional function. If a good fitting curve cannot be found for each data point (the correlation coefficient R 2 < 0.9) of the fitting curve, Steps 3 and 4 should be repeated at least five times until the curve is well-fitted (the correlation coefficient R 2 ≥ 0.9).

[0012] 5. Measure the resistivity of the moraine soil compacted subgrade on-site: Use the MOEN-0715B-type soil resistivity measuring instrument to measure the on-site resistivity of the moraine soil compacted subgrade by the four-electrode method (prior art). According to the formula ρ = 2πaV / I, the value of the on-site soil resistivity is obtained, where V is the potential difference between the voltage electrode and the auxiliary electrode, I is the alternating current between the grounding electrode and the current electrode, and a is the spacing of the grounding rods. Repeat the resistivity measurement 2 - 4 times at the same point, and take the average value as the resistivity test result of the moraine soil compacted subgrade. It should be noted that the test object in this Step 5 is the moraine soil containing boulders. Since the contact area between the boulders is too small (1 - 10 cm 2 ), the influence on the overall electrical conductivity is very small. The propagation path of the conduction current in the soil mass will bypass the relatively high-resistance boulder part and selectively flow through the soil part with only soil particles with a particle size less than 2 mm and low resistance, rather than through the non-actual flow path. Therefore, the resistivity of the moraine soil compacted subgrade measured on-site in this Step 5 is only the resistivity of the soil part S.

[0013] 6. Calculate the overall dry density of the on-site soil material: Based on the relationship between the soil resistivity and the dry density obtained from the indoor test in Step 4, substitute the resistivity of the on-site soil part material S measured on-site into the fitting curve of ρ = f(ρ dS ) obtained in Step 4 to calculate the dry density ρ dSinsi of the on-site soil part S. According to the formula ρ dinsi = ρ ds · ρ dG / [P · ρ dSinsi+(1 - P)·ρ dG The overall dry density ρ of the in - situ soil material is calculated dinsi : where ρ dSinsi is the dry density of the in - situ soil part S; ρ dG is the dry density of the gravel part G, and P is the gravel content.

[0014] 7. Measuring the maximum dry density of the in - situ soil material: Take 5 groups of loose soil samples with a weight of 6 kg from the site, and use the dry - soil method introduced in the "Code for Highway Geotechnical Tests" (JTG 3430—2020) to measure the maximum dry density ρ dmax in the compaction test for each group of specimens. Since the moraine soil contains large - sized particles, it has a certain impact on obtaining the maximum dry density, and the maximum dry density needs to be corrected. First, sieve the specimen through a 40 - mm sieve (ordinary), take out the particles larger than 40 mm, and obtain its percentage p. Then, for the part less than 40 mm, conduct a compaction test again according to the "Code for Highway Geotechnical Tests" (JTG 3430—2020), and correct the maximum dry density obtained from the test according to the following formula:

[0015]

[0016] In the formula: ρ′ dmax is the corrected maximum dry density, calculated to 0.01 g / cm 3 ; G′ S is the bulk specific gravity of the particles with a particle size larger than 40 mm, calculated to 0.01.

[0017] 8. Detection of the compaction degree of the moraine soil subgrade: Through the overall dry density ρ dSinsi of the in - situ soil material calculated in step 6 and the corrected maximum dry density ρ′ dmax measured in the compaction test in step 7, the actual compaction degree of the moraine soil subgrade is calculated by the formula K = ρ d / ρ′ dmax ×100%.

[0018] In the above - mentioned in - situ test method for the compaction performance of moraine soil containing boulders, further, in step 1, when conducting the sieve analysis test of the subgrade material, the difference Δm between the total mass of the soil samples above and below the sieve after sieving and the total mass of the soil sample before sieving shall not be greater than 1% of the total mass of the specimen.

[0019] In the above - mentioned in - situ test method for the compaction performance of moraine soil containing boulders, further, in step 2, the hollow - cylinder mold barrel shall be made of polyvinyl chloride (PVC) insulating material.

[0020] In the above - mentioned in - situ test method for the compaction performance of moraine soil containing boulders, preferably, in step 2, the electrode shall be a copper disc with a diameter of 50 mm.

[0021] In the above in-situ test method for the compaction performance of boulder till soil, further, in step 2, when drawing the fitting curve of the dry density of the soil part and the resistivity, at least 5 data points should be taken.

[0022] In the above in-situ test method for the compaction performance of boulder till soil, further, in step 3, the spacing between the auxiliary grounding rods connected to the grounding test line should be greater than 20 times their insertion depth (the insertion depth is 3 - 5 cm).

[0023] In the above in-situ test method for the compaction performance of boulder till soil, further, in step 6, when detecting the compaction degree of the soil body material, the screened particle size should be greater than 40 mm.

[0024] The technical solution principle of the in-situ test method for the compaction performance of boulder till soil of the present invention is as follows: Based on the predetermined relationship between the dry density of the soil part and the resistivity in the till subgrade material, the dry density of the soil part is derived by combining the measured resistivity of the subgrade material in-situ on site. Combining the dry density and content of the gravel part and the dry density of the soil part, the overall dry density of the subgrade material is derived, and the actual compaction degree of the subgrade material is calculated by taking the ratio with the maximum dry density of the subgrade material. When calculating the compaction degree of the subgrade material in the present invention, the size of the gravel particles in the soil body has no influence on the result but only relates to the content of the gravel. Therefore, the present invention is also applicable to the compaction degree detection of subgrade materials containing particles of different sizes (such as crushed stones, boulders, etc.).

[0025] For the technical measures of the above six steps, the key steps are Step 3, Step 6, and Step 8. In Step 3, soil materials with different dry densities after screening out gravel are taken for indoor resistivity testing, and the relationship curve between the dry density and resistivity of the soil part is obtained simply and conveniently. In Step 6, through the formula, using the dry density of the soil part, the content and dry density of the gravel part, the dry density of the overall subgrade material is directly calculated, mainly solving the problem of "time-consuming and laborious" in measuring the dry density of subgrade materials containing large particles. According to the derivation formula of resistivity and dry density in the present invention, it can be directly and simply obtained without separately testing the compaction degree of subgrade materials with different gravel contents. In Step 8, the compaction degree of the subgrade material is calculated by comparing the dry density measured on-site of the overall subgrade material with its maximum dry density, achieving the effect of quickly evaluating the compaction degree of the built part of the subgrade material during the subgrade construction process. Compared with the existing testing methods for subgrade compaction degree, the technical progress of the present invention lies in: compared with the nuclear density gauge determination method, the technical solution of the present invention has the advantages of safety and stability, no risk of radiation damage, simple equipment and clear principle, and has better engineering applicability and convenience for rapidly constructed engineering sites, facilitating timely detection of the project; compared with the sand replacement method for determining compaction degree, when the sand replacement method measures the moraine soil subgrade containing huge particles, once the test hole is near the gravel, the size of the test hole will be non-standard and the test result error will be large, while the technology of the present invention is applicable to the moraine soil subgrade containing huge particles, accurately calculates the dry density of the subgrade through the predetermined relationship between dry density and resistivity, and then evaluates its compaction degree, making the test result more accurate and the application range wider; compared with the indoor testing method, according to the "Technical Specifications for Highway Subgrade Construction" (JTG F10 - 2006), the indoor testing method needs to take samples and conduct tests on each layer of compacted soil, but for the moraine soil layer containing huge boulders, due to the large spatial variability of the huge boulder content, in order to obtain the compaction degree more accurately, it is necessary to increase the sample size, while the technical solution of the present invention can avoid the problems of low test efficiency and large discreteness of test results in indoor testing. Through multiple tests, the results of this method are true, reliable, and have high precision (the compaction degree precision is ±0.5%).

[0026] Compared with the prior art, the present invention has the following advantages and effects:

[0027] ① Low cost. All test equipment and materials are common instruments and consumables, which can be recycled and reused, reducing the test

[0028] cost.

[0029] ② The principle is simple and easy to understand, and the data accuracy is high. The technical principle is based on the predetermined relationship between the dry density and resistivity of soil,

[0030] The overall dry density of the soil material is calculated based on the resistivity of the figure measured on-site, and then its degree of compaction is evaluated. Compared with the complex process of traditional on-site testing methods, the present invention has higher accuracy.

[0031] ③ Simple operation. There are no large-scale instruments at the construction site, the instrument assembly is convenient, the test method is simple and easy to implement, and no professional technical personnel are required to operate, reducing manpower and material resources.

[0032] personnel operation, reducing manpower and material resources.

[0033] ④ Short measurement cycle, improving work efficiency. There is no need to repeatedly conduct indoor tests on soil samples with different large particle contents, nor to conduct on-site in-situ tests with a long process. It can be carried out synchronously with the subgrade construction process, greatly improving the construction inspection efficiency.

[0034] ⑤ Wide application range of the measurement method. In addition to being able to be applied to the compaction degree detection of moraine soil subgrade containing boulders, it is also applicable to the construction quality detection of various other subgrades containing large particles.

[0035] ⑥ It will not cause damage or other adverse effects to the construction site. Compared with the traditional in-situ testing method, the solution of the present invention does not need to drill holes or dig holes on the subgrade, does not cause damage to the compacted soil subgrade, and will not have an adverse impact on the existing subgrade foundation. Description of the Drawings

[0036] Figure 1 It is a block schematic diagram of an in-situ testing method for the compaction performance of moraine soil containing boulders;

[0037] Figure 2 It is a schematic diagram of the indoor soil sample resistivity testing device in step 2 of an in-situ testing method for the compaction performance of moraine soil containing boulders;

[0038] Figure 3 It is a schematic diagram of the current flow path during the resistivity measurement of the in-situ moraine soil subgrade material in step 3 of an in-situ testing method for the compaction performance of moraine soil containing boulders;

[0039] Figure 4 It is a schematic diagram of the test result of Example 1 of an in-situ testing method for the compaction performance of moraine soil containing boulders (fitting curve of soil partial dry density and resistivity)

[0040] Figure 5 It is a schematic diagram of the test result of Example 2 of an in-situ testing method for the compaction performance of moraine soil containing boulders (fitting curve of soil partial dry density and resistivity);

[0041] Figure 6 It is a comparison diagram of the test results of Example 1 and Comparative Test 1 of an in-situ testing method for the compaction performance of moraine soil containing boulders;

[0042] Figure 7 Comparison chart of test results of Example 1 and Example 2 of in-situ test method for compacting performance of boulder till soil and Comparative Test 2

[0043] Wherein: 1a - top copper bolt, 1b - bottom copper bolt, 2a - top cover, 2b - bottom cover, 3a - top copper electrode, 3b - bottom copper electrode, 4a - first copper rod, 4b - second copper rod, 5 - hollow cylindrical mold barrel, 6 - voltmeter, 7 - AC power supply, 8 - wire, 9 - specimen, 10 - grounding electrode, 11 - auxiliary grounding electrode, 12 - voltage electrode, 13 - current electrode, 14 - boulder part of till soil, 15 - soil part of till soil, 16 - actual current flow path, 17 - non-actual current flow path, 18 - MOEN-0715B type soil resistivity measuring instrument

[0044] All the above components are purchased on the market. Specific implementation mode

[0045] The following combines with the attached drawings to elaborate in detail on an in-situ test method for the compacting performance of boulder till soil in two embodiments and two comparative tests of the present invention.

[0046] Example 1:

[0047] The test site of Example 1 is a construction site (site 1) of a boulder till soil subgrade of an under-construction expressway. All the steps related to basic geotechnical tests (including Step 1) in the invention are strictly carried out with reference to the Specification for Standard Methods of Soil Tests (GB / T 50123 - 2019). For the convenience of understanding, the flow chart of an in-situ test method for the compacting performance of boulder till soil of the present invention is shown in Figure 1 as follows.

[0048] According to Figure 1 , Figure 2 , Figure 3 it can be known that an in-situ test method for the compacting performance of boulder till soil has the following steps:

[0049] 1. Sampling and calculating gravel content: Take a loose soil sample with a mass of m at the in-situ site of the compacted subgrade of boulder till soil containing boulder components. According to the Standard for Classification of Soils for Engineering Purposes (GB / T 50145 - 2007), the loose soil sample material is divided into a soil part S with a particle size ≤ 2 mm and a gravel part G with a particle size > 2 mm by the screening method. Each time when screening the soil sample, 500 g of the soil sample should be weighed, and the measured mass of the sample should be accurate to 1 g. Finally, the total mass m S of the soil part and the total mass m G of the gravel part of the loose soil sample are obtained. To ensure the accuracy of the screening test, after screening, according to the formula Δm = |m - (m G+ m S)|Calculate the difference between the total mass of the samples above and below the sieve after screening and the total mass of the samples before screening, Δm, which is less than 1% of the total mass of the soil sample. The gravel content P of the compacted soil of the roadbed is calculated by the formula P = m G / (m G+ m S )×100%, the gravel content P of the modified site is 30%.

[0050] 2. Calculate the dry density of the soil and gravel parts: Calculate the dry density of the soil part S and the gravel part G respectively. For the soil part S, test its density ρ according to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019) Si With moisture content w Si , and by the formula Calculate the dry density ρ of the soil portion S dSi , three parallel tests should be carried out on the same soil sample, and the average value of the three parallel test results is taken as the dry state density of the soil sample, that is, Where: Si The density and ρ obtained from a single parallel test dSi is the dry density obtained from a single parallel test, w Si The moisture content and ρ obtained from a single parallel test dS is the dry density of the soil part S. For the gravel part G, an oven (ordinary) was used to dry the sample at a temperature of 110°C for 12 hours. The dry density of the gravel part G was measured according to the Geotechnical Test Method Standard (GB / T50123-2019). dG .

[0051] 3. Indoor measurement of soil resistivity: According to the Geotechnical Test Method Standard (GB / T 50123-2019), five cylindrical moraine soil compaction samples (height 100 mm, diameter 50 mm) with different dry densities were prepared using the sample pressing method. The wet soil mass m1 required to prepare the first compaction sample is calculated according to the formula m1 = (1 + 0.01w s )ρ dS V is determined, and the wet soil mass m of the remaining four compacted samples is i , i = 2, 3, 4, 5 is obtained by increasing the wet soil mass m0 of the first compacted sample by 2% four times; where: m i is the wet soil mass of the ith compacted sample, w S is the moisture content of wet soil, ρ dS is the dry density of the soil sample, and V is the volume of the sample press. When preparing the sample, pour the wet soil into the sample press (ordinary), press the soil sample tightly with the piston, and then take it out. The dry density of the compacted sample corresponding to different wet soil masses can be calculated by the formula ρ dSi =m i / (1+0.01ws )V,i = 1, 2, 3, 4, 5. It is calculated; where: ρ dSi is the dry density of the i-th compacted sample, m i is the wet soil mass of the i-th compacted sample, w S is the moisture content of the wet soil, and V is the volume of the sample press. The resistivity of five prepared specimens 9 with different dry densities is measured respectively. As Figure 2 shown, the specimen 9 is placed in a hollow cylindrical mold tube 5 with an inner diameter of 50 mm, an outer diameter of 52 mm, and an internal height of 100 mm. The upper and lower parts of the hollow cylindrical mold tube 5 are respectively provided with a top cover 2a and a bottom cover 2b made of the same material, with a diameter of 60 mm and a thickness of 5 mm, and a copper bolt 1. On the top and bottom of the specimen 9, disc-shaped top copper electrodes 3a and disc-shaped bottom copper electrodes 3b with a diameter of 50 mm and a thickness of 2 mm are placed, and the specimen 9 is sealed with the top cover 2a and the bottom cover 2b. The copper bolt 1a of the top seat and the copper bolt 1b of the bottom seat are connected to an external power supply 7 (an alternating current with a constant voltage of 35 V and a constant frequency of 60 Hz) through a wire 8. The copper bolt 1a of the top seat and the copper bolt 1b of the bottom seat are respectively in contact with the disc-shaped top copper electrode 3a and the disc-shaped bottom copper electrode 3b inside the mold tube 5. A top copper rod 4a and a bottom copper rod 4b are inserted into the cylindrical specimen. The vertical distance between the top copper rod 4a and the bottom copper rod 4b is the same as the distances from the top copper rod 4a and the bottom copper rod 4b to the bottom and the top respectively (both are 33.3 mm). The potential difference ΔV dSi between the top copper rod 4a and the bottom copper rod 4b is measured respectively for five specimens 8 with different dry densities (ρ i ), i = 1 - 5), and then according to the formula the resistivity (ρ i ), i = 1 - 5) of the specimen 8 is calculated: In the formula, S is the electrode area; L is the electrode spacing; I is the current intensity, and ΔV i is the potential difference.

[0052] 4. Calculate the relationship between the dry density and resistivity of the soil part: According to the dry densities (ρ dSi ), i = 1 - 5) and resistivities (ρ i ), i = 1 - 5) of the five compacted samples, draw the relationship curve ρ = f(ρ dS ), and fit it in the form of an inverse proportional function. The fitting curve result is as Figure 3 shown. If a good fitting curve cannot be found for each data point (the correlation coefficient R 2 of the fitting curve < 0.9), steps 3 and 4 should be repeated at least five times until the curve is well-fitted (the correlation coefficient R 2 of the fitting curve ≥ 0.9).

[0053] 5. On-site measurement of resistivity of moraine compacted roadbed: Use MOEN-0715B soil resistivity meter18 to conduct on-site resistivity measurement of moraine compacted roadbed, such as Figure 4 As shown. The value of the on-site soil resistivity is obtained according to the formula ρ=2πaV / I, where V is the potential difference between the voltage electrode 12 and the auxiliary electrode 11, I is the alternating current between the grounding electrode 10 and the current electrode 13, and a is the distance between the grounding rods. Repeat the resistivity test 2-4 times at the same point, and take the average value as the resistivity test result of the moraine compacted roadbed. It should be noted that the test object of this step 5 is moraine soil containing boulders. Since the contact area between the gravels is too small (1~10cm 2 ), which has little effect on the overall conductivity. The propagation path of the conductive current 16 in the soil will bypass the relatively high-resistance gravel part 14, and selectively flow through the low-resistance soil part 15 containing only soil particles with a particle size less than 2 mm, and will not pass through the non-actual flow path 17. Therefore, the resistivity of the compacted moraine roadbed measured on-site in this step 5 is only the resistivity of the soil part S.

[0054] 6. Calculate the overall dry density of the soil material on site: Based on the relationship between soil resistivity and dry density obtained from the indoor test in step 4, substitute the resistivity of the soil material S measured on site into the ρ=f(ρ dS ) is used to calculate the dry density ρ of the on-site soil part S. dSinsi According to the formula ρ dinsi =ρ ds ·ρ dG / [P·ρ dSinsi +(1-P)·ρ dG ] Calculate the overall dry density of the on-site soil material ρ dinsi : where ρ dSinsi is the dry density of the on-site soil part S; ρ dG is the dry density of the gravel part G, and P is the gravel content.

[0055] 7. Measure the maximum dry density of soil materials on site: Take 5 groups of loose soil samples weighing 6 kg on site, and use the dry soil method introduced in the "Highway Geotechnical Test Code" (JTG 3430-2020) to measure the maximum dry density ρ of each group of samples in the compaction test. dmax . Because moraine soil contains giant particles, it has a certain impact on the maximum dry density, so it is necessary to correct the maximum dry density. First, pass the sample through a 40mm sieve (ordinary), take out particles larger than 40mm, and calculate their percentage p. The remaining part smaller than 40mm is compacted again according to the "Highway Geotechnical Test Code" (JTG 3430-2020), and the maximum dry density obtained from the test is corrected according to the following formula:

[0056]

[0057] where: ρ′ dmax is the maximum dry density after correction, calculated to 0.01 g / cm 3 ; G′ S is the bulk specific gravity of particles with a particle size greater than 40 mm, calculated to 0.01.

[0058] 8. Detection of the compaction degree of moraine soil subgrade: Through the overall dry density ρ of the on-site soil material calculated in step 6 dSinsi and the corrected maximum dry density ρ′ measured in the compaction test in step 7 dmax , from the formula K = ρ d / ρ′ dmax ×100%, the actual compaction degree of the moraine soil subgrade is calculated.

[0059] Through the above specific technical measures, the compaction degree of the embankment finally calculated by an in-situ test method for the compaction performance of boulder-containing moraine soil of the present invention is 96%, meeting the requirements for the compaction degree of highway subgrade.

[0060] Example 2:

[0061] To better test the general applicability of an in-situ test method for the compaction performance of boulder-containing moraine soil of the present invention, a test section (site 2) located in the same moraine soil distribution area but different from that in Example 1 is selected. The average size of the gravel in the subgrade of the test site in Example 2 is 20 mm larger than that in the test section in Example 1, but the overall gravel content is the same, both being 30%.

[0062] As Figure 1 shown, an in-situ test method for the compaction performance of boulder-containing moraine soil, the steps of which are:

[0063] 1. Sampling and calculating the gravel content: Take a loose soil sample with a mass of m from the in-situ site of the compacted moraine soil subgrade containing boulder components. According to the "Standard for Engineering Classification of Soils" (GB / T 50145-2007), the loose soil sample material is divided into the soil part S with a particle size ≤ 2 mm and the gravel part G with a particle size > 2 mm by the screening method. Each time the soil sample is screened, 500 g of the soil sample should be weighed, and the measured mass of the sample should be accurate to 1 g. Finally, the total mass m of the soil part of the loose soil sample S and the total mass m of the gravel part G are obtained. To ensure the accuracy of the screening test, after the screening is completed, according to the formula Δm = |m - (m G+ m S )|, calculate the difference Δm between the total mass of the samples above and below the sieve after screening and the total mass of the sample before screening. This value is less than 1% of the total mass of the soil sample. The gravel content P of the compacted subgrade soil is calculated by the formula P = mG / (m G+ m S )×100%, the gravel content P of the modified site is 30%.

[0064] 2. Calculate the dry density of the soil and gravel parts: Calculate the dry density of the soil part S and the gravel part G respectively. For the soil part S, test its density ρ according to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019) Si With moisture content w Si , and by the formula Calculate the dry density ρ of the soil portion S dSi , three parallel tests should be carried out on the same soil sample, and the average value of the three parallel test results is taken as the dry state density of the soil sample, that is, Where: Si The density and ρ obtained from a single parallel test dSi is the dry density obtained from a single parallel test, w Si The moisture content and ρ obtained from a single parallel test dS is the dry density of the soil part S. For the gravel part G, an oven (ordinary) was used to dry it at a temperature of 110°C for 12 hours. The density of the dried sample was tested according to the "Standard for Geotechnical Test Methods" (GB / T50123-2019), and the result was the dry density ρ of the gravel part G. dG .

[0065] 3. Indoor measurement of soil resistivity: According to the Geotechnical Test Method Standard (GB / T 50123-2019), five cylindrical moraine soil compaction samples (height 100 mm, diameter 50 mm) with different dry densities were prepared using the sample pressing method. The wet soil mass m1 required to prepare the first compaction sample is calculated according to the formula m1 = (1 + 0.01w s )ρ dS V is determined, and the wet soil mass m of the remaining four compacted samples is i , i = 2, 3, 4, 5 is obtained by increasing the wet soil mass m0 of the first compacted sample by 2% four times; where: m i is the wet soil mass of the ith compacted sample, w S is the moisture content of wet soil, ρ dS is the dry density of the soil sample, and V is the volume of the sample press. When preparing the sample, pour the wet soil into the sample press (ordinary), press the soil sample tightly with the piston, and then take it out. The dry density of the compacted sample corresponding to different wet soil masses can be calculated by the formula ρ dSi =m i / (1+0.01w s )V,i=1,2,3,4,5. Calculated; where: ρ dSiis the dry density of the i-th compacted sample, m i is the wet soil mass of the i-th compacted sample, w S is the moisture content of the wet soil, and V is the volume of the sample compactor. The resistivity of five prepared specimens with different dry densities 9 was measured respectively. As Figure 2 shown, the specimen 9 was placed into the hollow cylindrical mold tube 5 with an inner diameter of 50 mm, an outer diameter of 52 mm, and an internal height of 100 mm. The upper and lower parts of the mold tube 5 were respectively provided with a top cover 2a and a bottom cover 2b made of the same material, with a diameter of 60 mm and a thickness of 5 mm, and a copper bolt 1. Disc-shaped top copper electrodes 3a and disc-shaped bottom copper electrodes 3b with a diameter of 50 mm and a thickness of 2 mm were placed on the top and bottom of the specimen 8, and the specimen 9 was sealed using the top cover 2a and the bottom cover 2b. The copper bolt 1a of the top seat and the copper bolt 1b of the bottom seat were connected to an external power supply 7 (alternating current with a constant voltage of 35 V and a constant frequency of 60 Hz) through a wire 8. The copper bolt 1a of the top seat and the copper bolt 1b of the bottom seat were respectively in contact with the disc-shaped top copper electrode 3a and the disc-shaped bottom copper electrode 3b inside the mold tube 5. Upper copper rods 4a and 4b were inserted into the cylindrical specimen. The vertical distance between the copper rods 4a and 4b was the same as the distances from the upper copper rods 4a and 4b to the bottom and the top respectively (both were 33.3 mm). The potential difference ΔV dSi between the copper rods 4a and 4b was measured respectively for the specimens 8 with five different dry densities (ρ i , i = 1 to 5) using a voltmeter 6, and then the resistivity (ρ of the specimen 8, i = 1 to 5) was calculated according to the formula i : In the formula, S is the electrode area; L is the electrode spacing; I is the current intensity, and ΔV i is the potential difference.

[0066] 4. Calculate the relationship between the dry density and resistivity of the soil part: According to the dry densities (ρ dSi , i = 1 to 5) and resistivities (ρ i , i = 1 to 5) of the five compacted samples, a relationship curve of dry density and resistivity ρ = f(ρ dS ) was plotted and fitted in the form of an inverse proportional function. The result of the fitted curve is as Figure 3 shown. If a good fitting curve cannot be found for each data point (the correlation coefficient R 2 of the fitting curve < 0.9), steps 3 and 4 should be repeated at least five times until the curve is well-fitted (the correlation coefficient R 2 of the fitting curve ≥ 0.9).

[0067] 5. Measure the resistivity of the moraine soil compacted subgrade on-site: Use a MOEN-0715B type soil resistivity measuring instrument 18 to measure the on-site resistivity of the moraine soil compacted subgrade, as Figure 4As shown. The value of the on-site soil resistivity is obtained according to the formula ρ = 2πaV / I, where V is the potential difference between the voltage electrode 12 and the auxiliary electrode 11, I is the alternating current between the grounding electrode 10 and the current electrode 13, and a is the spacing of the grounding rods. The resistivity is measured 2 - 4 times at the same point, and the average value is taken as the resistivity test result of the compacted moraine soil subgrade. It should be noted that the test object in step 5 is the moraine soil containing boulders. Since the contact area between the gravels is too small (1 - 10 cm 2 ), it has little impact on the overall electrical conductivity. The propagation path of the conduction current 16 in the soil mass will bypass the relatively high-resistance gravel part 14 and selectively flow through the low-resistance soil part 15 containing only soil particles with a particle size less than 2 mm, rather than passing through the non-actual flow path 17. Therefore, the resistivity of the compacted moraine soil subgrade measured on-site in step 5 is only the resistivity of the soil part S.

[0068] 6. Calculate the overall dry density of the on-site soil material: Based on the relationship between the soil resistivity and the dry density obtained from the indoor test in step 4, substitute the resistivity of the soil part material S measured on-site into the fitting curve of ρ = f(ρ dS ) obtained in step 4 to calculate the dry density ρ dSinsi of the on-site soil part S. According to the formula ρ dinsi = ρ ds ·ρ dG / [P·ρ dSinsi + (1 - P)·ρ dG , calculate the overall dry density ρ dinsi of the on-site soil material: where ρ dSinsi is the dry density of the on-site soil part S; ρ dG is the dry density of the gravel part G, and P is the gravel content.

[0069] 7. Measure the maximum dry density of the on-site soil material: Take 5 groups of loose soil samples with a weight of 6 kg on-site, and use the dry soil method introduced in the "Highway Geotechnical Test Regulations" (JTG 3430 - 2020) to measure the maximum dry density ρ dmax of each group of specimens in the compaction test. Since the moraine soil contains large particles, it has a certain impact on the determination of the maximum dry density, and the maximum dry density needs to be corrected. First, sieve the specimen through a 40 mm sieve (ordinary), take out the particles larger than 40 mm, and obtain their percentage p. The remaining part less than 40 mm is again subjected to the compaction test according to the "Highway Geotechnical Test Regulations" (JTG 3430 - 2020), and the maximum dry density obtained from the test is corrected according to the following formula:

[0070]

[0071] In the formula: ρ′ dmaxis the maximum dry density after correction, calculated to 0.01 g / cm 3 ; G′ S is the bulk specific gravity of particles larger than 40 mm in particle size, calculated to 0.01.

[0072] 8. Compaction degree detection of moraine soil subgrade: Through the overall dry density ρ of the on-site soil material calculated in step 6 dSinsi and the corrected maximum dry density ρ′ measured in the compaction test in step 7 dmax , from the formula K = ρ d / ρ′ dmax ×100% to calculate the actual compaction degree of the moraine soil subgrade.

[0073] For Example 2, the compaction degree of the embankment finally calculated by the in-situ test method for the compaction performance of moraine soil containing boulders according to the present invention is 97%, meeting the requirements of the compaction degree of the expressway subgrade. By comparing the relationship curves of the dry density and resistivity obtained in step 3 of Example 1 and Example 2, it can be found that (as Figure 4 and Figure 5 shown), the morphological trends of the two fitting curves are basically the same, and the positions of the partial dry density points of the subgrade soil predicted on the fitting curve by the soil resistivity measured on-site in the two examples are basically coincident, which shows that the size of the gravel in the subgrade soil has no influence on the relationship between the dry density and resistivity in the present invention. Therefore, the final subgrade compaction degree is not affected by the spatial variability of the gravel and is only related to the gravel content in the soil, indicating that the present invention is very suitable for the compaction performance detection of moraine soil containing boulders.

[0074] Comparative test 1:

[0075] To compare the advantages and disadvantages of the technical solution of the present invention with the detection method of the compaction degree of the subgrade by the pit filling sand test method in the commonly used "Code for In-Situ Testing of Highway Subgrade and Pavement (JTG 3450—2019)", Comparative test 1 uses the same test subgrade site as in Example 1, and tests the in-situ embankment compaction degree according to the pit filling sand test method in the "Code for In-Situ Testing of Highway Subgrade and Pavement (JTG 3450—2019)". Since the embankment is compacted in five layers in total, in order to comprehensively compare the compaction degree, the technical solution of the present invention and the pit filling sand test method are respectively used to detect the five-layer embankment, and the five compaction degree test results obtained by the two methods and the comparison are as Figure 6 shown.

[0076] The compaction degrees of different soil layers obtained by using the technical solution of the present invention are 97%, 96.7%, 97.1%, 97.2%, and 97.8% respectively, and the range is 0.4%. The compaction degrees of different soil layers obtained by using the sand replacement method by digging a pit are 86.1%, 91.2%, 89.1%, 95.0%, and 85.1% respectively, and the range is as high as 9.9%. By comparing the experimental results of the two methods, it can be found that the compaction degree measured by the sand replacement method by digging a pit has extremely large fluctuations when applied to the test of moraine soil embankments containing boulders, and stable and accurate test results cannot be obtained. This is because the wide distribution of boulders in the moraine soil embankment will cause the size of the test hole near the gravel to be easily deformed and non-standard during the sand replacement method test, and there is a large spatial variability in the test results, resulting in large result errors. In contrast, the compaction degree results of different soil layers obtained by the technical solution of the present invention are stably around 97%, indicating that the results are not affected by the distribution of gravel in the embankment, and also verifying the applicability and reliability of an in-situ test method for the compaction performance of moraine soil containing boulders in the present invention in the moraine soil subgrade.

[0077] Comparative test 2:

[0078] To compare the accuracy, advantages and disadvantages of the technical solution of the present invention with the method of calculating the compaction degree by the heavy compaction test in the commonly used "Highway Geotechnical Test Regulations (JTG E40)", in comparative test 2, the method of calculating the compaction degree by the heavy compaction test in the "Highway Geotechnical Test Regulations (JTG E40)" was used to measure the compaction degree of the embankments at site 1 in Example 1 and site 2 in Example 2 respectively. The comparison between comparative test 2 and the test results of Example 1 and Example 2 is as Figure 7 shown.

[0079] According to the compaction degrees of the two sites obtained from the aforementioned Example 1 and Example 2, they are 96% and 97% respectively. According to comparative test 2, based on the heavy compaction method in the "Highway Geotechnical Test Regulations (JTG E40)", the compaction degrees of the two sites are 96.2% and 97.3% respectively. This shows that the results obtained by using the technical solution of the present invention are very consistent with the results required by the current technical specifications, and the technical solution of the present invention has good general applicability. However, in the technical solution of the present invention, only the relationship curve between the resistivity and the dry density of the soil needs to be obtained through experiments, and the overall dry density of the soil can be directly deduced for different embankment soil layers. In contrast, in comparative test 2, based on the heavy compaction method in the "Highway Geotechnical Test Regulations (JTG E40)", the compaction test needs to be carried out on different soil layers to measure the overall dry density of the gravel-containing part. The presence of gravel makes this heavy compaction test very time-consuming and labor-consuming. Obviously, the technical solution provided by the present invention has the advantages of time-saving and labor-saving, and the obtained data has extremely high accuracy and reliability.

[0080] The above are only the preferred embodiments of the present invention and are not intended to limit the invention. Any simple modifications, changes, and equivalent structural transformations made to the above embodiments based on the essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An in-situ test method for the compaction performance of boulder till soil, the steps of which are as follows: A. Sampling and calculating gravel content: Take a loose soil sample with a mass of m from the in-situ compacted subgrade of moraine soil containing boulders. Use the sieving method to divide the loose soil sample material into the soil part S with a particle size ≤ 2 mm and the gravel part G with a particle size > 2 mm. Each time when sieving the soil sample, weigh the soil sample, and the measured mass of the sample should be accurate to 1 g to obtain the total mass m S of the soil part and the total mass m G of the gravel part of the loose soil sample. After sieving, calculate the difference Δm between the total mass of the upper and lower samples on the sieve after sieving and the total mass of the sample before sieving according to the formula Δm = |m - (m G+ m S )|. This value should be less than 1% of the total mass of the soil sample. The gravel content P of the compacted subgrade soil is calculated by the formula P = m G / (m G+ m S ) × 100%; B. Calculate the dry densities of the soil part and the gravel part: Calculate the dry densities of the soil part S and the gravel part G respectively. For the soil part S, test its density ρ Si and the water content w Si , and through the formula calculate the dry density ρ dSi of the soil part S. For the same soil sample, 3 parallel tests should be carried out, and the average value of the results of the 3 parallel tests should be taken as the density of the soil sample in the dry state, that is Where: ρ Si is the density obtained from a single parallel test measurement, ρ dSi is the dry density obtained from a single parallel test measurement, w Si is the moisture content obtained from a single parallel test measurement, ρ dS is the dry density of the soil portion S. For the gravel portion G, it is dried in an oven with the temperature controlled at 110 °C for 12 hours. The dry density ρ of the gravel portion G is obtained according to the measured density of the dried sample dG ; C. Indoor measurement of soil partial resistivity: Five cylindrical moraine soil compaction samples with different dry densities are prepared by the method of pressing samples with a sample press. The wet soil mass m1 required to prepare the first compaction sample is determined according to the formula m1=(1 + 0.01w s )ρ dS V, and the wet soil masses m i , i = 2, 3, 4, 5 of the remaining four compaction samples are obtained by increasing the wet soil mass m0 of the first compaction sample four times in increments of 2%; where: m i is the wet soil mass of the i-th compaction sample, w S is the wet soil moisture content, ρ dS is the dry density of the soil sample, V is the volume of the sample press. During sample preparation, pour the wet soil into the sample press, compact the soil sample through the piston and then take it out. The dry density of the compaction sample corresponding to different wet soil masses is calculated by the formula ρ dSi = m i / (1 + 0.01w s )V, i = 1, 2, 3, 4, 5; where: ρ dSi is the dry density of the i-th compaction sample, m i is the wet soil mass of the i-th compaction sample, w S is the wet soil moisture content, V is the volume of the sample press. Measure the resistivity of the five prepared samples (9) with different dry densities respectively. Place the sample into a hollow cylindrical mold tube with an inner diameter of 50 mm, an outer diameter of 52 mm, and an internal height of 100 mm. The upper and lower parts of the mold tube are respectively equipped with a top cover and a bottom cover made of the same material, with a diameter of 60 mm and a thickness of 5 mm, and copper bolts. Place disk-shaped top copper electrodes (3a) and disk-shaped bottom copper electrodes (3b) with diameters of 50 mm and thicknesses of 2 mm respectively on the top and bottom of the sample. Use the top cover and the bottom cover to seal the sample. The copper bolts of the top seat and the copper bolts of the bottom seat are connected to an external power supply through wires and are respectively in contact with the disk-shaped top copper electrode (3a) and the disk-shaped bottom copper electrode (3b) inside the mold tube. Insert upper copper bars and into the cylindrical sample. The vertical distance between the two copper bars and is the same as the distances from the upper copper bar and to the bottom and the top respectively. Use a voltmeter (6) to measure the potential difference ΔV dSi between the copper bars and for the five samples with different dry densities ρ i , i = 1 - 5 respectively, and then calculate the resistivity ρ of the sample according to the formula i , i = 1 - 5: In the formula, S is the electrode area; L is the electrode spacing; I is the current intensity, and ΔV i is the potential difference; D. Calculate the relationship between the partial dry density of the soil and the resistivity: Based on the dry densities ρ dSi ,i = 1 - 5 and the resistivities ρ i ,i = 1 - 5 measured in steps (B) and (C), plot the relationship curve between the dry density and the resistivity ρ = f(ρ dS ). For the fitting curve that cannot be found for each data point, steps (C) and (D) should be repeated at least five times until the curve is fitted; E. Measure the resistivity of the compacted subgrade of till soil on-site: Use a MOEN-0715B soil resistivity measuring instrument, and adopt the four-electrode method to measure the on-site resistivity of the compacted subgrade of till soil. Obtain the value of the on-site soil resistivity according to the formula ρ = 2πaV / I, where V is the potential difference between the voltage electrode and the auxiliary electrode, I is the alternating current between the grounding electrode and the current electrode, and a is the spacing of the grounding rods. Repeat the resistivity test 2 - 4 times at the same position, and take the average value as the resistivity test result of the compacted subgrade of till soil. The test object of this step is till soil containing boulders, which selectively flows through the soil part with soil particles having a particle size less than 2 mm with low resistance. The resistivity of the compacted subgrade of till soil measured on-site in this step is only the resistivity of the soil part S. F. Calculate the overall dry density of the in-situ soil material: Based on the relationship between soil resistivity and dry density obtained from the laboratory test in step (D), substitute the resistivity of the partial soil material S measured in-situ into the fitting curve of ρ = f(ρ dS ) obtained in step (D) to obtain the dry density ρ dSinsi of the partial in-situ soil S. According to the formula ρ dinsi = ρ ds · ρ dG / [P · ρ dSinsi + (1 - P) · ρ dG , calculate the overall dry density ρ dinsi of the in-situ soil material: where ρ dSinsi is the dry density of the partial in-situ soil S; ρ dG is the dry density of the gravel part G, and P is the gravel content; G. Measuring the maximum dry density of the in-situ soil material: Take 5 groups of undisturbed soil samples from the site, and use the dry soil method to measure the dry density ρ of each group of specimens in the compaction test. dmax , the till contains large particles. First, sieve the specimen through a 40-mm sieve, take out the particles larger than 40 mm, and obtain their percentage p. Then, conduct a compaction test on the remaining part smaller than 40 mm. Correct the dry density obtained from the test according to the following formula: where: ρ′ dmax is the maximum dry density after correction, calculated to 0.01 g / cm 3 ; G′ S is the bulk specific gravity of particles with a particle size greater than 40 mm, calculated to 0.01; H. Compaction degree detection of moraine soil subgrade: The overall dry density ρ of the on-site soil material calculated in step (F) dSinsi and the corrected maximum dry density ρ' measured in the compaction test in step (G) dmax , the actual compaction degree of the moraine soil subgrade is calculated by the formula K = ρ d / ρ' dmax × 100%.

2. The in-situ test method for the compaction performance of boulder till soil according to claim 1, characterized in that: In the step (A) described above, when conducting the sieve analysis test of the subgrade material, the difference Δm between the total mass of the soil samples above and below the sieve after sieving and the total mass of the soil sample before sieving shall not be greater than 1% of the total mass of the sample.

3. The in-situ test method for the compaction performance of boulder till soil according to claim 1, characterized in that: In the step (B) described above, the hollow cylinder mold barrel shall be made of polyvinyl chloride insulating material.

4. The in-situ test method for the compaction performance of boulder till soil according to claim 1, characterized in that: In the step (B) described above, the electrode shall be a copper disc with a diameter of 50 mm.

5. The in-situ test method for the compaction performance of boulder till soil according to claim 1, characterized in that: In the step (B) described above, when drawing the fitting curve of the dry density and resistivity of the soil part, at least 5 data points shall be taken.

6. The in-situ test method for the compaction performance of boulder till soil according to claim 1, characterized in that: In the step (C) described above, the spacing of the auxiliary grounding rods connected to the grounding test line shall be greater than 20 times its insertion depth.

7. An in-situ test method for the compaction performance of boulder till soil according to claim 1, characterized in that: In the step (F) described above, when conducting the compaction degree detection of the soil material, the sieved particle size shall be greater than 40 mm.

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