Method for accurately testing compactness of fine-grained soil of built dam

Abstract

The application discloses a method for accurately testing compaction degree of fine-grained soil of built dam, which comprises the following steps: step one, drilling and taking undisturbed samples; step two, testing natural density and natural water content of each undisturbed sample; step three, calculating dry density of each undisturbed sample; step four, classifying fine-grained soil and taking disturbed samples of each kind of soil; step five, carrying out compaction test on each disturbed sample; and step six, calculating and determining compaction degree of each undisturbed sample. The application effectively solves the problem that the prior art cannot accurately test compaction degree of fine-grained soil at different depths of built dam, and has the advantages of being capable of accurately testing compaction degree of fine-grained soil at different depths of built dam, and the testing result is accurate and reliable.

Description

Technical Field

[0001] This invention relates to the fields of engineering surveying and geotechnical testing, specifically a method for accurately testing the compaction degree of fine-grained soil in an existing dam. More specifically, it is a method that uses drilling sampling to test the dry density of fine-grained soil and its matching maximum dry density, in order to accurately determine the compaction degree of fine-grained soil at different depths within the dam body of an existing dam. Background Technology

[0002] Current standards stipulate that engineering surveys should ascertain the filling quality of dam and embankment fill, with compaction degree being the most important technical parameter for measuring the filling quality of fine-grained soil dam and embankment fill. However, the testing technology system in the water conservancy and hydropower industry lacks specific regulations for compaction degree testing, typically relying on laboratory tests and in-situ tests for indirect determination. In-situ tests include sand-filling and water-filling methods, both of which require sampling from shallow excavated pits on the surface. This limited testing depth makes it impossible to obtain the compaction degree of fine-grained soil at different depths within the dam and embankment, thus failing to comprehensively evaluate the filling quality. Laboratory tests can measure the dry density of undisturbed samples, and it is customary to use the average maximum dry density of the entire dam fill as the maximum dry density at any measuring point, dividing the two to calculate the soil compaction degree. However, the results often differ significantly from actual conditions.

[0003] Therefore, it is essential to develop a new method to accurately test the compaction degree of fine-grained soil at different depths in existing dams. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an accurate method for testing the compaction degree of fine-grained soil in an existing dam. This method utilizes drilling sampling to test the dry density of fine-grained soil and its matching maximum dry density, thereby accurately determining the compaction degree of fine-grained soil at different depths in the existing dam body. The results are accurate and reliable, and based on this, the quality of dam body filling can be comprehensively evaluated. This effectively solves the problem that existing technologies cannot accurately test the compaction degree of fine-grained soil at different depths in an existing dam.

[0005] To achieve the above objectives, the technical solution of the present invention is: a method for accurately testing the compaction degree of fine-grained soil in an existing embankment, characterized by comprising the following steps.

[0006] Step 1: Drilling and collecting undisturbed core samples;

[0007] Step 2: Conduct natural density and natural moisture content tests on each undisturbed sample;

[0008] Step 3: Calculate the dry density of each undisturbed sample;

[0009] Step 4: Classify fine-grained soils and take disturbance samples for each type of soil;

[0010] Step 5: Conduct compaction tests on each disturbed sample;

[0011] Step 6: Calculate and determine the compaction degree of each undisturbed sample.

[0012] In the above technical solution, in step one, when drilling on the dam to the predetermined sampling position, a thin-walled soil sampler is used to collect undisturbed rock core samples. The static pressure method or the heavy hammer method is used for sampling. The sampling interval is 2 to 5 m. The undisturbed samples are numbered from top to bottom as Y1, Y2, ..., Yn.

[0013] In the above technical solution, in step two, the natural density and natural moisture content of each undisturbed sample are tested in accordance with the requirements of current technical standards.

[0014] Through experiments, the natural densities of the undisturbed samples Y1, Y2, ..., Yn were determined to be ρ1, ρ2, ..., ρn, respectively. n The natural moisture contents are ω1, ω2, ..., ω n .

[0015] In the above technical solution, step three uses the formula. Calculate the dry density of each undisturbed sample; then the dry density of a certain undisturbed sample is... where i = 1, 2, ..., n;

[0016] After calculation, the dry densities of the undisturbed samples Y1, Y2, ..., Yn are ρ, ... d 1 ρ d 2 、…、ρ d n .

[0017] In the above technical solution, in step four, the type of soil in the undisturbed core sample is identified, and disturbed samples are taken for different soil types.

[0018] To meet the test requirements, the mass of the disturbed sample for each type of soil shall not be less than 5 kg; the disturbed sample shall be taken from a location adjacent to the undisturbed sample; the disturbed sample shall be indicated by different codes according to the type of fine-grained soil, with silt, silty clay and clay designated as I, II and III respectively.

[0019] In the above technical solution, in step five, a compaction test is performed on each disturbed sample according to the requirements of current technical standards to obtain the maximum dry density ρ of the sample. dmax The maximum dry density of a certain type of soil is expressed by ρ. dmax * If we express this as ρ, then the maximum dry densities of silt, silty clay, and clay are respectively ρ dmax Ⅰ ρ dmax Ⅱ ρdmax Ⅲ .

[0020] In the above technical solution, in step six, the formula is used. Calculate the compaction degree of each undisturbed sample, then the compaction degree of a certain undisturbed sample is: Calculations show that the compaction degrees of undisturbed samples Y1, Y2, ..., Yn are λ1, λ2, ..., λn, respectively. n .

[0021] The method for accurately testing the compaction degree of fine-grained soil in an existing embankment provided by this invention has the following beneficial effects:

[0022] (1) By drilling and sampling tests, the compaction degree of fine soil at different depths of the dam body can be obtained. Based on this, the quality evaluation of the dam body filling can be carried out in a complete manner, overcoming the limitation that the current field test is only used for shallow layers.

[0023] (2) By taking undisturbed core samples and matching disturbed samples, the dry density of fine-grained soil at any test depth and the matching maximum dry density can be obtained (this maximum dry density is variable, rather than the fixed value of the average maximum dry density of fine-grained soil in the entire dam). The results are accurate and reliable. It effectively solves the problem that existing technologies cannot accurately test the compaction of fine-grained soil at different depths in existing dams. That is, existing in-situ tests can only be conducted by taking samples from test pits with a shallow excavation depth on the ground surface. The test depth is small and it is impossible to obtain the compaction of fine-grained soil at different depths in the dam body. Therefore, it is impossible to completely evaluate the filling quality of the dam. Existing technologies use indoor tests to take undisturbed samples to test the dry density. At the same time, it is customary to use the average maximum dry density of the filling soil of the entire dam as the maximum dry density of any measuring point. The compaction of the soil is calculated by dividing the two. However, the results are often very different from the actual situation and are inaccurate. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the method for accurately testing the compaction degree of fine-grained soil in an existing dam, as described in this invention. Detailed Implementation

[0025] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, these descriptions do not constitute a limitation of the present invention and are merely illustrative. The advantages of the present invention will become clearer and easier to understand through this description.

[0026] Referring to the attached diagram, the method for accurately testing the compaction degree of fine-grained soil in an existing embankment includes the following steps:

[0027] Step 1: Drilling and collecting undisturbed core samples;

[0028] Step 2: Conduct natural density and natural moisture content tests on each undisturbed sample;

[0029] Step 3: Calculate the dry density of each undisturbed sample;

[0030] Step 4: Classify fine-grained soils and take disturbance samples for each type of soil;

[0031] Step 5: Conduct compaction tests on each disturbed sample;

[0032] Step Six: Calculate and determine the compaction degree of each undisturbed sample (e.g., Figure 1 (As shown).

[0033] Furthermore, in step one, when drilling on the dam, to maintain the natural water content of the undisturbed core sample, the use of flushing fluid should be controlled, especially within 0.5m of the predetermined sampling location, the use of water or mud is strictly prohibited. Upon reaching the predetermined sampling location, a thin-walled sampler should be used to collect the undisturbed core sample. To further reduce disturbance to the natural structure of the undisturbed core sample, static pressure or heavy hammer method should be used during sampling. The sampling interval is generally 2-5m, with smaller intervals for smaller dam heights and larger intervals for larger dam heights. When the soil type changes or the soil density differs significantly, sampling should be conducted promptly, regardless of the aforementioned sampling interval restrictions. The undisturbed samples can be numbered from top to bottom as Y1, Y2, ..., Yn.

[0034] Furthermore, in step two, in accordance with the requirements of current technical standards, natural density (represented by the symbol ρ) and natural moisture content (represented by the symbol ω) tests are conducted on each undisturbed sample;

[0035] Through experiments, the natural densities of the undisturbed samples Y1, Y2, ..., Yn were determined to be ρ1, ρ2, ..., ρn, respectively. n The natural moisture contents are ω1, ω2, ..., ω n .

[0036] Furthermore, in step three, the formula is used. Calculate the dry density of each undisturbed sample (using the symbol ρ). d (represented by), then the dry density of a certain undisturbed sample is where i = 1, 2, ..., n;

[0037] After calculation, the dry densities of the undisturbed samples Y1, Y2, ..., Yn are ρ, ... d 1 ρ d 2 、…、ρ d n .

[0038] Furthermore, in step four, the soil type of the undisturbed core samples taken from the drilling is identified, and disturbed samples are taken for different soil types; that is, when n sets of undisturbed core samples are taken, the on-site identification of these undisturbed samples involves certain types of soil such as silt, silty clay, and clay; after determining the soil types involved, disturbed samples are taken.

[0039] To meet the test requirements, the mass of the disturbed sample for each type of soil shall not be less than 5 kg; the disturbed sample shall be taken from a location adjacent to the undisturbed sample; the disturbed sample may be represented by different codes according to the type of fine-grained soil, with silt, silty clay and clay designated as I, II and III respectively.

[0040] Furthermore, in step five, according to current technical standards, a compaction test is performed on each disturbed sample to obtain the maximum dry density ρ of the sample. dmax The maximum dry density of a certain type of soil is expressed by ρ. dmax * If we express this as ρ, then the maximum dry densities of silt, silty clay, and clay are respectively ρ dmax Ⅰ ρ dmax Ⅱ ρ dmax Ⅲ .

[0041] Furthermore, in step six, the formula is used. Calculate the degree of compaction (denoted by the symbol λ) for each undisturbed sample. Then, the degree of compaction for a given undisturbed sample is: (* indicates the soil type corresponding to the undisturbed sample Yi, selected from I, II, and III according to different soil types, i=1, 2, ..., n); After calculation, the compaction degrees of the undisturbed samples Y1, Y2, ..., Yn are λ1, λ2, ..., λn, respectively. n .

[0042] The method of this invention determines the dry density required for compaction through laboratory tests on undisturbed soil samples, and uses the maximum dry density of the compaction test that matches the soil type of the undisturbed soil sample, resulting in accurate test results. At the same time, it obtains compaction data at different depths of the dam body, making the dam filling quality evaluation conclusions based on this more reliable and comprehensive.

[0043] This invention provides a method for obtaining the compaction degree of fine-grained soil. It offers a direct testing method that is simple to operate and highly efficient. The compaction degree results are obtained directly based on conventional laboratory tests, resulting in high accuracy and versatility. It can be applied to compaction degree testing in different locations and for different types of fine-grained soil, and has a wider range of applications. Besides testing the compaction degree of artificial fill soil in existing embankments, it can also be used for natural sedimentary soils. This overcomes the limitations of existing technologies that rely on geophysical exploration methods such as shear waves and surface waves to indirectly calculate the compaction degree of fine-grained soil using a large amount of statistical data, which is complex and labor-intensive. This method overcomes the shortcomings of time-consuming methods and the low accuracy of compaction degree obtained solely through geophysical exploration test results and statistical formulas. It also overcomes the shortcomings of existing technologies that rely on formulas relating dry density to dynamic penetration resistance and moisture content, resulting in low accuracy of compaction degree testing and the need to establish different formulas for different locations or soil types, leading to low versatility. Furthermore, it overcomes the drawbacks of existing technologies that obtain soil compaction degree through numerical simulation and inversion analysis of the compaction process, which are complex, labor-intensive, time-consuming, and only applicable to compaction degree testing during road construction.

[0044] Example

[0045] The present invention will now be described in detail using an example of testing the compaction degree of fine-grained soil in an existing dam. This invention also has guiding significance for testing the compaction degree of fine-grained soil in other existing dams.

[0046] This embodiment uses the method described in this invention for accurately testing the compaction degree of fine-grained soil in an existing dam to test the compaction degree of fine-grained soil in the dam body, including the following steps:

[0047] Step 1: In this embodiment, a certain existing dam is a soil-based seepage-proof core gravel dam with a maximum height of 25.7m. Drilling is carried out on the dam crest using borehole ZK24, with a planned core sample interval of 5m. During the drilling process, the soil type changed, and the sampling location was adjusted. Ultimately, core samples were taken at borehole depths of 2.0m, 7.0m, 12.0m, 16.0m, 18.5m, 20.0m, and 25.0m, with a sampling interval of 1.5 to 5m. When reaching the predetermined sampling location, a thin-walled soil sampler was used to collect the core samples. Static pressure or heavy hammer blows method was used for sampling. There are a total of 7 core samples, numbered from top to bottom, such as Y1, Y2, ..., Y7.

[0048] In step two, in accordance with current technical standards, the natural density (denoted by the symbol ρ) and natural moisture content (denoted by the symbol ω) of each undisturbed sample were tested. After the tests, the natural densities of undisturbed samples Y1, Y2, ..., Yn were ρ1 = 18.2 g / cm³. 3 ρ2 = 19.2 g / cm³3 ρ3 = 18.9 g / cm³ 3 ρ4 = 19.1 g / cm³ 3 ρ5 = 18.8 g / cm³ 3 ρ6 = 19.1 g / cm³ 3 ρ7 = 19.7 g / cm³ 3 Their natural water contents are ω1=22.2%, ω2=23.6%, ω3=24.5%, ω4=25.5%, ω5=20.3%, ω6=22.7%, and ω7=26.8%, respectively.

[0049] In step three, the formula is used. Calculate the dry density of each undisturbed sample (using the symbol ρ). d (represented by), then the dry density of a certain undisturbed sample is (where i = 1, 2, ..., 7); After calculation, the dry densities of the undisturbed samples Y1, Y2, ..., Y7 are ρ 1 d =14.9g / cm 3 ρ 2 d =15.5g / cm 3 ρ 3 d =15.2g / cm 3 ρ 4 d =15.2g / cm 3 ρ 5 d =15.6g / cm 3 ρ 6 d =15.6g / cm 3 ρ 7 d =15.5g / cm 3 .

[0050] In step four, seven undisturbed core samples were collected during drilling, all of which were fine-grained soils. Two of the undisturbed samples were silty clay and five were clay, meaning that this borehole involved both silty clay and clay soils. Disturbance samples were collected for each soil type. 5.8 kg of silty clay disturbance samples were collected near Y5 and Y6, and 6.3 kg of clay disturbance samples were collected near Y1, Y2, Y3, Y4, and Y7. The silty clay and clay disturbance samples were designated as II and III, respectively.

[0051] In step five, compaction tests are conducted on the two types of disturbed soil samples according to current technical standards to obtain the maximum dry density ρ of the samples. dmax The maximum dry densities of silty clay and clay are ρ and ρ, respectively. Ⅱ dmax=16.5g / cm 3 ρ Ⅲ dmax =15.8g / cm 3 .

[0052] In step six, the formula is used. Calculate the degree of compaction (denoted by the symbol λ) for each undisturbed sample. Then, the degree of compaction for a given undisturbed sample is: (* indicates the soil type corresponding to the undisturbed sample Yi, selected from II and III according to different soil types, i=1, 2, ..., 7); After calculation, the compaction degrees of the undisturbed samples Y1, Y2, ..., Yn are λ1=0.94, λ2=0.98, λ3=0.96, λ4=0.96, λ5=0.95, λ6=0.94, and λ7=0.98, respectively. The specific tests are shown in Table 1 below;

[0053] Table 1. Results of compaction testing using the embodiments of the present invention in this example.

[0054]

[0055] Conclusion: In this embodiment, the dry density required for compaction was determined by the method of the present invention through indoor tests on undisturbed soil samples. The maximum dry density of the compaction test was matched with the soil type of the undisturbed soil sample. The test results were accurate, and compaction data at different depths of the dam body were obtained simultaneously. The method of the present invention for accurately testing the compaction of fine-grained soil in an existing dam was accurate and reliable in this embodiment. The dam body filling quality evaluation conclusions based on this method are more reliable and comprehensive.

[0056] This invention provides a method for accurately testing the compaction degree of fine-grained soil in existing dams. This method has been successfully tested in the investigation of several dangerous reservoir reinforcement projects, including Meidian Reservoir in Wuhan City, Hubei Province, Sandaohe Reservoir in Nanzhang County, Hubei Province, and Zhengjiahe Reservoir in Xiaogan City, Hubei Province. This method overcomes the limitations of current field tests, which are only applicable to shallow layers. The results are accurate and reliable, allowing for a comprehensive evaluation of the dam body and embankment filling quality. It effectively solves the problem of testing the compaction degree of fine-grained soil at different depths in existing dams.

[0057] 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.

[0058] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A method for accurately testing the compaction degree of fine-grained soil in an existing embankment, characterized in that: Includes the following steps, Step 1: Drilling and core sampling; When drilling to the predetermined sampling location on the embankment, use a thin-walled soil sampler to collect undisturbed core samples. Use static pressure method or heavy hammer method for sampling; The sampling interval is 2-5m; The undisturbed samples are numbered from top to bottom as Y1, Y2, ..., Yn; Step 2: Conduct natural density and natural moisture content tests on each undisturbed sample; Step 3: Calculate the dry density of each undisturbed sample; Step 4: Classify fine-grained soils and take disturbance samples for each type of soil. Disturbance samples are represented by different codes according to the type of fine-grained soil: silt, silty clay, and clay are designated as I, II, and III, respectively. Disturbance samples are taken from the vicinity of the undisturbed sample to obtain a disturbance sample that matches the undisturbed sample. Step 5: Conduct compaction tests on each disturbed sample to obtain the maximum dry density ρ of the sample. dmax ; Step 6: Calculate and determine the compaction degree of each undisturbed sample; using the formula... Calculate the compaction degree of each undisturbed sample; the compaction degree of the undisturbed sample is then calculated. Where i = 1, 2, ..., n; Then, the dry densities of the undisturbed samples Y1, Y2, ..., Yn are respectively ρ d 1 ρ d 2 、…、ρ d n The maximum dry density of a certain type of soil is expressed by ρ. dmax * If we express this as ρ, then the maximum dry densities of silt, silty clay, and clay are respectively ρ dmax Ⅰ ρ dmax Ⅱ ρ dmax Ⅲ Calculations show that the compaction degrees of undisturbed samples Y1, Y2, ..., Yn are λ1, λ2, ..., λn, respectively. n .

2. The method for accurately testing the compaction degree of fine-grained soil in an existing embankment according to claim 1, characterized in that: In step two, in accordance with current technical standards, natural density and natural moisture content tests were conducted on each undisturbed sample to obtain the natural densities of undisturbed samples Y1, Y2, ..., Yn as ρ1, ρ2, ..., ρn, respectively. n The natural moisture contents are ω1, ω2, ..., ω n .

3. The method for accurately testing the compaction degree of fine-grained soil in an existing embankment according to claim 2, characterized in that: In step three, the formula is used. Calculate the dry density of each undisturbed sample; then the dry density of any undisturbed sample is: .

4. The method for accurately testing the compaction degree of fine-grained soil in an existing embankment according to claim 3, characterized in that: In step four, the type of undisturbed soil sample taken from the drilling core is identified, and disturbed samples are taken for different soil types. To meet the test requirements, the mass of the disturbed sample for each soil type is greater than or equal to 5 kg.

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