High-density electric quantitative interpretation method based on soil resistivity calculation model

Abstract

The invention discloses a high-density electric quantitative interpretation method based on a soil resistivity calculation model, and the method specifically comprises the steps: 1, measuring the physical characteristics of a sampling soil body in a detection region, carrying out the orthogonal test of main influence factors of the resistivity of the soil body, and analyzing the primary and secondary factors which affect the change of the resistivity; 2, selecting three factors with large influence degrees to carry out a quantitative test, and determining a quantitative relationship between the resistivity of the soil sample and the influence factors; step 3, based on the quantitative relation between the resistivity and each influence factor, fitting to obtain a soil resistivity calculation model of the detection area; 4, carrying out a nondestructive testing field test on the detection area to obtain an apparent resistivity image of the area; and 5, performing qualitative and quantitative double interpretation on a field detection result by combining an indoor test and a field test. The problem that in the prior art, high-density television resistivity result analysis depends on manual subjective experience judgment, and large uncertainty exists is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing methods for water conservancy projects, and relates to a high-density electrical quantitative interpretation method based on a soil resistivity calculation model. Background Art

[0002] China is widely distributed with areas of soil erosion where the ecological environment is fragile. The impact of human activities is the decisive factor for the sharp reduction of soil erosion in such areas in recent years. At present, the construction of silt dam projects as a measure for soil and water conservation often adopts the method of using local materials, and the anti-seepage design of the dam body is less considered. The construction procedure is too simple compared with the earth-rock dam, which leads to the dam body's infiltration line being too high after water storage, and it is very easy to have soil penetration damage such as pipe burst and leakage. As the operation time increases, the risk of dam failure will continue to increase, posing a huge threat to the safety of life and property of local and downstream people. Therefore, it is necessary to study the detection method to determine the leakage path and identify the leakage channel inside the dam, so as to provide a reliable basis and effective guarantee for the risk removal, reinforcement, expansion and transformation of the silt dam and the safe operation.

[0003] Traditional drilling methods not only consume a lot of manpower and material resources, but also cause damage to the dam structure. In recent years, geophysical exploration methods that study the differences in the physical characteristics of the detection object to determine the occurrence, burial depth and scale of hidden dangers inside the dam body have become increasingly mature, providing efficient and reliable new tools for non-destructive, fast and large-scale detection of leakage hazards in silt dams. As an important method of geophysical electrical exploration, the high-density electrical method is based on the electrical differences of media such as soil and rock. It solves hydrological, engineering and environmental geological problems by observing and studying the distribution laws of artificially established underground stable electric fields. It has the advantages of low cost, high efficiency and rich data information. The structure of a silt dam is similar to that of a traditional homogeneous earth dam, but the dam height is usually lower. The detection range of the high-density resistivity method can better cover the interior of the silt dam, with high detection accuracy and good detection effect. However, there are problems such as extensive construction methods, complex characteristics of dam-building materials, and uneven compaction in the silt dam, which have a significant impact on the accurate exploration of the resistivity characteristics of the dam-building soil. In addition, the resistivity of the rock and soil is closely related to its own moisture content, soil ion concentration and other factors. The various influencing factors are correlated, making the conductive properties of the rock and soil medium extremely complex. Although the high-density resistivity method can use the apparent resistivity difference obtained by inversion of detection data to reflect the location and nature of the hidden danger site, and provide reliable technical support for the leakage detection of the dam, the analysis of the apparent resistivity results depends on manual subjective experience and judgment, and there is a large uncertainty. This seriously restricts the application and promotion of the high-density resistivity tomography method in the non-destructive detection of leakage in silt dams.

[0004] Therefore, it is necessary to systematically study the resistivity characteristics of the silt dam soil and accurately determine the quantitative relationship between soil resistivity and different influencing factors, which is of great reference significance for assisting high-density electrical method in internal leakage detection and parameter inversion of silt dam. Summary of the invention

[0005] The purpose of the present invention is to provide a high-density television resistivity interpretation method based on a soil resistivity calculation model, which solves the problem that the analysis of high-density television resistivity results in the prior art relies on manual subjective experience judgment and has great uncertainty.

[0006] The technical solution adopted by the present invention is a high-density electrical quantitative interpretation method based on a soil resistivity calculation model, specifically:

[0007] Step 1: measure the physical properties of the sampled soil in the detection area, conduct orthogonal tests on the main influencing factors of the soil resistivity, and analyze the primary and secondary factors affecting the resistivity change;

[0008] Step 2, select three factors with the largest influence to conduct quantitative tests, and determine the quantitative relationship between the resistivity of the soil sample and the influencing factors;

[0009] Step 3: Based on the quantitative relationship between resistivity and various influencing factors, a soil resistivity calculation model of the detection area is fitted;

[0010] Step 4: Conduct nondestructive testing field tests on the detection area to obtain an apparent resistivity image of the area;

[0011] Step 5: Combine indoor and field tests to perform both qualitative and quantitative interpretation of the on-site detection results, so as to conduct a comprehensive analysis of the leakage situation in the detected area.

[0012] The present invention is also characterized in that:

[0013] Step 1 is as follows:

[0014] Step 1.1, conduct various geotechnical tests on the original soil samples to determine the natural moisture content / %, optimal moisture content / %, maximum dry density, plastic limit / %, and liquid limit / % of the samples, in preparation for the calculation and analysis of the tests;

[0015] Step 1.2, soil ion concentration, moisture content, soil compaction and temperature are selected as four factors, each factor considers three levels and selects three representative low, medium and high contents according to the experimental objectives, and designs and conducts orthogonal experiments;

[0016] Step 1.3, based on the orthogonal test results, obtain the data sum value K of different factors at different levels, the average value Kavg of the K value and the range value R, use Kavg to draw the factor average value graph, observe its decline rate to assist analysis, and use the range R to determine the primary and secondary order of the influence of the four factors on soil resistivity.

[0017] Step 2 is as follows:

[0018] Step 2.1, the test design is to measure the corresponding resistivity of soil samples with n different moisture contents, M different densities and M different soil ion concentrations; firstly, a sufficient amount of collected soil samples is weighed, and the dried soil samples required for the test are prepared in an oven, and the different water addition amounts required for the soil samples at n different moisture contents are calculated using formula (1), and 2n groups of water samples are prepared according to the calculation results of the water addition amounts at n different moisture contents, and the homemade water samples are divided into two parts, which are recorded as water sample A and water sample B;

[0019]

[0020] Where: m ω is the amount of water required for the soil sample (g); ω0 is the drying moisture content (%); m is the mass of the soil sample at the drying moisture content (g); ω' is the required moisture content of the soil sample (%);

[0021] Step 2.2: According to the water sample B standard with n different water contents (i.e. water samples B1 to B n ) corresponding to the preparation of M B water samples (i.e. water sample B 1-1 ~B 1-M ; B 2-1 ~B 2-M ; ... ; B n-1 ~B n-M ), and obtain n*M portions of water sample B; calculate the mass of ionic substances corresponding to M different soil ion concentrations at n different water contents according to the following formula (2), prepare n*M portions of corresponding ionic substances according to the calculation results, and add the ionic substances to n*M portions of water sample B respectively, and prepare samples C (i.e., water sample C) at n different water contents and M different soil ion concentrations. 1-1 ~C 1-M ; C 2-1 ~C 2-M ;……;C n-1 ~C n-M ), a total of n*M parts;

[0022]

[0023] Where: m N is the mass of ionic substances required to be added to the soil sample (g); m ω is the required amount of water added (g); ω Nis the soil ion concentration (%);

[0024] Step 2.3, calculate the internal volume of the Miller Soil Box device used in the test, and weigh the mass of soil samples corresponding to M different compaction degrees at n different moisture contents according to the following formula (3), and prepare the corresponding n*M soil samples according to the calculation results;

[0025] m'=ρ dmax P i V(1+0.01ω0) (3)

[0026] Where: m' is the required amount of soil sample (g); ρ dmax is the maximum dry density (g / cm 3 );P i is the density (%); V is the internal volume of the Miller Soil Box (cm 3 );

[0027] Step 2.4: According to the water sample A standard with n different water contents (i.e. water samples A1 to A n ) each prepared M water samples (i.e., water sample A 1-1 ~A 1-M ; A 2-1 ~A 2-M ;……;A n-1 ~A n-M ), a total of n*M parts, use a spray pot to take water sample A respectively, spray the water sample evenly on the soil prepared in 2.3, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours;

[0028] Step 2.5, randomly select a soil sample prepared in 2.3, make n*M copies, record as soil sample D, use a spray bottle to take sample C respectively, spray the water sample evenly on the prepared soil material D, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water sample C to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours;

[0029] Step 2.6, repeat steps 2.4 and 2.5 until the prepared soil sample reaches the n kinds of moisture content, M kinds of different densities and M kinds of different soil ion concentrations required by the test, and the difference between the actual and the preset values ​​should be controlled within the range of ±1%;

[0030] Step 2.7, prepare the final sample by light layered compaction method. Divide the soil sample weighed in step 2.6 into two equal parts, first pour the first part of the soil sample into the Miller Soil Box, level the surface and compact it to the required height, then roughen the surface, then pour the second part of the soil sample, level the surface again and compact it to the required height;

[0031] Step 2.8, through the above steps, remolded soil samples with specified moisture content, soil ion concentration and density can be accurately prepared, with a total of 2*n*M parts;

[0032] Step 2.9, the resistivity of each soil sample is measured 2 to 3 times, and the arithmetic mean is taken as the final measurement result. Based on the control variable method, the resistivity change law of the soil under different soil ion concentrations, different water contents, and different densities is studied in turn.

[0033] Step 3 is as follows:

[0034] Step 3.1, determine the relationship between the influencing factors and the resistivity of the soil sample based on the test results in 2.9. Consider whether there is such an influence in the actual project and remove 1 to 2 factors appropriately;

[0035] Step 3.2, choose to use the generalized Archie formula to fit the soil resistivity and the calculation model between the influencing factors determined in 3.1, that is, the soil resistivity calculation model, the expression is as follows:

[0036] ρ F =Kφ -m ω -n +f(φ,ω) (4)

[0037] Where: F is the resistivity of soil sample, Ω·m; φ is the influencing factor of 1%; ω is the influencing factor of 2%; K, m, n are soil parameters; f(φ,ω) is an additional function.

[0038] In step 4, a nondestructive testing field test is carried out on the detection area using the DUK-2A high-density electrical measurement system to obtain an apparent resistivity image of the area.

[0039] Step 5 is as follows:

[0040] Step 5.1, using the soil resistivity calculation model of indoor test 3.2, convert the apparent resistivity result obtained by field detection in step 4 into an intuitive water content value;

[0041] Step 5.2, combine the indoor test, field test and the soil sample results obtained in step 1.1 to conduct a comprehensive analysis of the leakage situation in the tested area. Specifically: if the moisture content of the soil sample is lower than the natural moisture content, it means there is no leakage here; if the moisture content of the soil sample exceeds the natural moisture content and is less than the liquid limit, there may be leakage, which should be judged in combination with on-site investigation. If water seepage is found in the downstream measuring line, it is confirmed that there is leakage; if the moisture content of the soil sample exceeds the liquid limit, there is leakage here;

[0042] Step 5.3: Use SketchUp to draw a three-dimensional model of the dam body, select the apparent resistivity image and place it at the actual detection location, draw a schematic diagram of the leakage channel, and determine the location of the leakage risk based on the results of Step 5.2.

[0043] The beneficial effects of the present invention are as follows: the method of the present invention conducts orthogonal tests and quantitative tests on the factors affecting soil resistivity based on the physical properties of the soil sampled on site, determines the order of priority of the factors affecting the soil resistivity and obtains a soil resistivity calculation model. Then, the soil resistivity calculation model of the indoor test is combined with the on-site high-density electrical detection to better reveal the resistivity characteristics of the soil for silt dam construction. The resistivity imaging of the on-site high-density electrical detection can only qualitatively analyze the leakage of the silt dam. The resistivity calculation model of the soil resistivity can be used to convert the resistivity determined by human subjectivity into an objective and accurate water content, thereby realizing the precise analysis of the properties of the abnormal body with hidden dangers. The invention can lay the foundation for the qualitative and quantitative interpretation of leakage hazards, and has important value for accurately locating leakage hazards of silt dams by assisting high-density resistivity tomography methods. The applicability of high-density resistivity tomography technology in detecting leakage hazards of silt dams has been further verified, expanding the application prospects of the technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a flow chart of a high-density electrical quantitative interpretation method based on a soil resistivity calculation model of the present invention;

[0045] Figure 2 It is a schematic diagram of the average values ​​of orthogonal test factors in step 1 of embodiment 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0046] Figure 3 It is a schematic diagram of the relationship curve between NaCl concentration and soil resistivity at different water contents in step 2 of embodiment 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0047] Figure 4 It is a schematic diagram of the relationship curve between water content and soil resistivity at different NaCl concentrations in step 2 of embodiment 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0048] Figure 5 It is a schematic diagram of the relationship curve between compaction degree and soil resistivity at different water contents in step 2 of embodiment 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0049] Figure 6 It is a schematic diagram of the relationship curve between water content and soil resistivity at different compaction degrees in step 2 of embodiment 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0050] Figure 7 It is a schematic diagram of the relationship surface between different compaction degrees, different water contents and soil resistivity in step 3 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0051] Figure 8 It is a schematic diagram of the schematic diagram of the layout position of the Dongmengou silt dam survey line in step 4 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0052] Fig. 9 It is a schematic diagram of the apparent resistivity image of the survey line 1 using the Wenner and Schiebe profile configuration in step 4 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0053] Fig.10 It is a schematic diagram of the apparent resistivity image of the survey line 2 using the Wenner and Schiebe profile configuration in step 4 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0054] Fig.11 It is a schematic diagram of the apparent resistivity image of the survey line 3 using the Wenner and Schiebe profile configuration in step 4 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0055] Fig.12 It is a schematic diagram of the apparent resistivity image of the survey line 4 using the Wenner and Schiebe profile configuration in step 4 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0056] Fig.13 It is a schematic diagram of the apparent resistivity image of the survey line 5 using the Wenner and Schiebe profile configuration in step 4 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention;

[0057] Fig.14 It is a schematic diagram of the leakage channel of the Dongmengou silt dam in step 5 of Example 1 of the high-density electrical quantitative interpretation method based on the soil resistivity calculation model of the present invention. DETAILED DESCRIPTION

[0058] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0059] The present invention provides a high-density electrical quantitative interpretation method based on a soil resistivity calculation model, such as Figure 1 As shown, the specific steps are as follows:

[0060] Step 1: Measure the physical properties of the sampled soil in the detection area, conduct orthogonal tests on the main influencing factors of soil resistivity, and analyze the primary and secondary factors affecting the resistivity change, specifically:

[0061] Step 1.1, conduct various geotechnical tests on the original soil samples to determine the natural moisture content / %, optimal moisture content / %, maximum dry density, plastic limit / %, and liquid limit / % of the samples, in preparation for the calculation and analysis of the tests;

[0062] Step 1.2, soil ion concentration, moisture content, soil compaction and temperature are selected as four factors, each factor considers three levels and selects three representative low, medium and high contents according to the experimental objectives, and designs and conducts orthogonal experiments;

[0063] Step 1.3, based on the orthogonal test results, obtain the data sum K of different factors at different levels, the average value Kavg of the K value, and the range value R. Use Kavg to draw the factor average value diagram, observe its decline rate to assist analysis, and use the range R to determine the primary and secondary order of the four factors' influence on soil resistivity (the larger R is, the more significant the influence effect is).

[0064] Step 2: Based on the primary and secondary factors affecting the resistivity change of soil samples, three factors with the largest influence are selected for quantitative testing, and the quantitative relationship between the resistivity of soil samples and the influencing factors is determined, specifically:

[0065] Step 2.1, the test design is to measure the corresponding resistivity of soil samples with n different moisture contents, M different densities and M different soil ion concentrations; firstly, a sufficient amount of collected soil samples is weighed, and the dried soil samples required for the test are prepared in an oven, and the different water addition amounts required for the soil samples at n different moisture contents are calculated using formula (1), and 2n groups of water samples are prepared according to the calculation results of the water addition amounts at n different moisture contents, and the homemade water samples are divided into two parts, which are recorded as water sample A and water sample B;

[0066]

[0067] Where: m ω is the amount of water required for the soil sample (g); ω0 is the drying moisture content (%); m is the mass of the soil sample at the drying moisture content (g); ω' is the required moisture content of the soil sample (%);

[0068] Step 2.2: According to the water sample B standard with n different water contents (i.e. water samples B1 to B n ) corresponding to the preparation of M B water samples (i.e. water sample B 1-1 ~B 1-M ; B 2-1 ~B 2-M ; ... ; B n-1 ~B n-M ), and obtain n*M portions of water sample B; calculate the mass of ionic substances corresponding to M different soil ion concentrations at n different water contents according to the following formula (2), prepare n*M portions of corresponding ionic substances according to the calculation results, and add the ionic substances to n*M portions of water sample B respectively, and prepare samples C (i.e., water sample C) at n different water contents and M different soil ion concentrations. 1-1 ~C 1-M ; C 2-1 ~C 2-M ;……;C n-1 ~C n-M ), a total of n*M parts;

[0069]

[0070] Where: m N is the mass of ionic substances required to be added to the soil sample (g); m ω is the required amount of water added (g); ω N is the soil ion concentration (%);

[0071] Step 2.3, calculate the internal volume of the Miller Soil Box device used in the test, and weigh the mass of soil samples corresponding to M different compaction degrees at n different moisture contents according to the following formula (3), and prepare the corresponding n*M soil samples according to the calculation results;

[0072] m'=ρ dmax P i V(1+0.01ω0) (3)

[0073] Where: m' is the required amount of soil sample (g); ρ dmax is the maximum dry density (g / cm 3 );P i is the density (%); V is the internal volume of the Miller Soil Box (cm 3 );

[0074] Step 2.4: According to the water sample A standard with n different water contents (i.e. water samples A1 to A n ) each prepared M water samples (i.e., water sample A 1-1 ~A 1-M ; A 2-1 ~A 2-M ;……;An-1 ~A n-M ), a total of n*M parts, use a spray pot to take water sample A respectively, spray the water sample evenly on the soil prepared in 2.3, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours;

[0075] Step 2.5, randomly select a soil sample prepared in 2.3, make n*M copies, record as soil sample D, use a spray bottle to take sample C respectively, spray the water sample evenly on the prepared soil material D, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water sample C to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours;

[0076] Step 2.6, repeat steps 2.4 and 2.5 until the prepared soil sample reaches the n kinds of moisture content, M kinds of different densities and M kinds of different soil ion concentrations required by the test, and the difference between the actual and the preset values ​​should be controlled within the range of ±1%;

[0077] Step 2.7, prepare the final sample by light layered compaction method. Divide the soil sample weighed in step 2.6 into two equal parts, first pour the first part of the soil sample into the Miller Soil Box, level the surface and compact it to the required height, then roughen the surface, then pour the second part of the soil sample, level the surface again and compact it to the required height;

[0078] Step 2.8, through the above steps, remolded soil samples with specified moisture content, soil ion concentration and density can be accurately prepared, with a total of 2*n*M parts;

[0079] Step 2.9, the resistivity of each soil sample is measured 2 to 3 times, and the arithmetic mean is taken as the final measurement result. Based on the control variable method, the resistivity variation law of the soil under different soil ion concentrations, different water contents, and different densities is studied in turn;

[0080] Step 3: Based on the quantitative relationship between resistivity and various influencing factors, the soil resistivity calculation model of the detection area is fitted, which is as follows:

[0081] Step 3.1, determine the relationship between the influencing factors and the resistivity of the soil sample based on the test results in 2.9. Consider whether there is such an influence in the actual project and remove 1 to 2 factors appropriately (a curve surface between the influencing factors and the resistivity of the soil can be drawn to assist understanding);

[0082] Step 3.2, choose to use the generalized Archie formula to fit the resistivity of the soil and the calculation model between the influencing factors determined in 3.1, that is, the soil resistivity calculation model, the expression is as follows (taking the remaining two types of influencing factors as an example, namely, influencing factor 1 and influencing factor 2), namely:

[0083] ρ F =Kφ -m ω -n +f(φ,ω) (4)

[0084] Where: F is the resistivity of soil sample (Ω·m); φ is the influencing factor 1 (%); ω is the influencing factor 2 (%); K, m, n are soil parameters; f(φ,ω) is an additional function.

[0085] Step 4: After the on-site inspection and instrument self-test preparation, a DUK-2A high-density electrical measurement system consisting of a multi-channel electrode converter and a DZD-6A multi-function DC electrical instrument is used to conduct non-destructive testing field tests on the test area to obtain the apparent resistivity image of the area, specifically:

[0086] Step 4.1: Conduct on-site inspection of the project area to be tested, conduct preliminary preparation of testing equipment including leakage inspection, line layout and parameter selection, and then select the universal Wenner device and Schiebe profile device mode to conduct non-destructive testing field tests in the test area. Conduct high-density electrical data collection;

[0087] Step 4.2, relying on the Lizheng high-density software, the collected data are converted, preprocessed and terrain corrected, and finally the apparent resistivity image of the field test is obtained by inversion calculation;

[0088] Step 5: Combine indoor and outdoor tests to conduct qualitative and quantitative dual interpretation of the on-site detection results, so as to conduct a comprehensive analysis of the leakage situation in the detected area; specifically:

[0089] Step 5.1, using the soil resistivity calculation model of indoor test 3.2, convert the apparent resistivity result obtained by field detection in step 4 into an intuitive water content value;

[0090] Step 5.2, combine the indoor test, field test and the soil sample results obtained in step 1.1 to conduct a comprehensive analysis of the leakage situation in the tested area. Specifically: if the moisture content of the soil sample is lower than the natural moisture content, it means there is no leakage here; if the moisture content of the soil sample exceeds the natural moisture content and is less than the liquid limit, there may be leakage, which should be judged in combination with on-site investigation. If water seepage is found in the downstream measuring line, it is confirmed that there is leakage; if the moisture content of the soil sample exceeds the liquid limit, there is leakage here;

[0091] Step 5.3: Use SketchUp to draw a three-dimensional model of the dam body, select the apparent resistivity image in the device mode with good image presentation effect and place it at the actual detection position, draw a schematic diagram of the leakage channel, and determine the location of the leakage risk in combination with the results of 5.2.

[0092] Example 1

[0093] An actual silt dam was selected as the research object, and the high-density electrical quantitative interpretation method based on the soil resistivity calculation model was applied to practice to verify the effectiveness of the method.

[0094] This embodiment selects the Dongmengou silt dam located in Jingbian County, Shaanxi Province, China as the research object. It is a control project mainly used to intercept runoff and sediment. The filling soil of the dam body is taken from the local surface loess, which has a single nature and the soil type is silty loam. The natural moisture content corresponding to the dam body soil is about 15%. The density of the dam body is uneven, and the value fluctuates between 79% and 87%. At present, the project is mainly composed of dam construction structures such as dam body, water discharge horizontal pipe, water culvert and spillway. The dam crest elevation of the Dongmengou silt dam is 107m, the maximum dam height is 27m, the dam crest width is 5m, and there are two horseways on the downstream dam slope, with elevations of 100m and 90m respectively. The silt storage capacity of the silt dam is 999,600 m 3 The flood storage capacity is 156,300 m 3 The designed siltation area is 16.77hm 2 , which is a large silt dam.

[0095] The high-density electrical quantitative interpretation method based on the soil resistivity calculation model is implemented in the following steps:

[0096] Step 1: measure the physical properties of the sampled soil in the detection area, conduct orthogonal tests on the main influencing factors of soil resistivity, and analyze the primary and secondary factors affecting the resistivity change; specifically:

[0097] Step 1.1, conduct multiple types of geotechnical tests on the loess collected in the inspected area to obtain the natural moisture content / %, optimal moisture content / %, maximum dry density, plastic limit / %, and liquid limit / % of the samples, as shown in Table 1;

[0098] Table 1 Characteristics of loess in soil resistivity test

[0099]

[0100] Step 1.2, considering the soil salinity, the soil ion is selected as Na + With Cl -Therefore, NaCl concentration, water content, soil compaction and temperature are selected as 4 factors, and 3 levels are considered for each factor. The content of each factor is shown in Table 2. Based on this, an orthogonal test is designed and carried out, and the test results are shown in Table 3;

[0101] Table 2 Orthogonal test factor level table

[0102]

[0103] Table 3 Orthogonal test design table

[0104]

[0105] Step 1.3, according to the orthogonal test results, the data sum value K, the average value Kavg and the range value R of different factors at different levels are obtained, see Table 4, and the factor average value diagram is drawn using Kavg as shown in Figure 2 As shown, the decline rate is observed to assist analysis, and the range R is used to determine the primary and secondary order of the four factors affecting soil resistivity;

[0106] Table 4 Orthogonal test analysis table

[0107]

[0108]

[0109] According to the comparison of R values ​​and the decreasing speed of each broken line in the average value diagram of orthogonal test factors, it is judged that the factor NaCl concentration is the optimal factor, followed by the factors of water content and compaction, and finally the factor of temperature.

[0110] Step 2: Based on the primary and secondary factors affecting the resistivity change of soil samples, three factors with the greatest influence (NaCl concentration, water content, and compaction degree) are selected for quantitative testing, and the quantitative relationship between the resistivity of soil samples and the influencing factors is determined; specifically:

[0111] Step 2.1, the test design is to measure the corresponding resistivity of 9 test soil samples with different moisture contents, 5 different densities and 5 different soil ion concentrations; firstly, a sufficient amount of collected soil samples is weighed, and the dried soil samples required for the test are prepared in an oven, and the different water addition amounts required for the soil samples at 9 different moisture contents are calculated using formula (1), and 18 groups of water samples are prepared according to the calculation results of the water addition amounts at 9 different moisture contents, and the homemade water samples are divided into two parts, recorded as water sample A and water sample B;

[0112]

[0113] Where: m ωis the amount of water required for the soil sample (g); ω0 is the drying moisture content (%); m is the mass of the soil sample at the drying moisture content (g); ω' is the required moisture content of the soil sample (%);

[0114] Step 2.2: Prepare 5 B water samples (i.e., water samples B1 to B9) according to the 9 water sample B standards with different water contents. 1-1 ~B 1-5 ; B 2-1 ~B 2-5 ; ... ; B n-1 ~B n-5 ), and 45 portions of water samples B were obtained. The masses of ionic substances corresponding to 5 different soil ion concentrations at 9 different water contents were calculated according to the following formula (2), and 45 portions of corresponding ionic substances were prepared according to the calculation results. The ionic substances were added to 45 portions of water samples B respectively, and samples C (i.e., water samples C) with 5 different soil ion concentrations at 9 different water contents were prepared. 1-1 ~C 1-5 ; C 2-1 ~C 2-5 ;……;C n-1 ~C n-5 ), 45 in total;

[0115]

[0116] Where: m N is the mass of ionic substances required to be added to the soil sample (g); m ω is the required amount of water added (g); ω N is the soil ion concentration (%);

[0117] Step 2.3, calculate the internal volume of the Miller Soil Box device used in the test, and weigh the mass of soil samples corresponding to 5 different compaction degrees at 9 different moisture contents according to the following formula (3), and prepare 45 corresponding soil samples according to the calculated results;

[0118] m'=ρ dmax P i V(1+0.01ω0) (3)

[0119] Where: m' is the required amount of soil sample (g); ρ dmax is the maximum dry density (g / cm 3 );P i is the density (%); V is the internal volume of the Miller Soil Box (cm 3 );

[0120] Step 2.4: According to the 9 water sample A standards with different water contents (i.e. water samples A1 to A n ) prepared 5 water samples each (i.e., water sample A1-1 ~A 1-5 ; A 2-1 ~A 2-5 ;……;A n-1 ~A n-5 ), a total of 45 parts, use a spray pot to take water sample A respectively, spray the water sample evenly on the soil prepared in 2.3, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it does not meet the test requirements, add water to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours;

[0121] Step 2.5, randomly select a soil sample prepared in 2.3, make n*M copies, record as soil sample D, use a spray bottle to take sample C respectively, spray the water sample evenly on the prepared soil material D, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water sample C to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours;

[0122] Step 2.6, repeat steps 2.4 and 2.5 until the prepared soil sample reaches the 9 moisture contents, 5 different densities and 5 different soil ion concentrations required by the test, and the difference between the actual and the preset values ​​should be controlled within the range of ±1%;

[0123] Step 2.7, prepare the final sample by light layered compaction method. Divide the soil sample weighed in step 2.4 into two equal parts, first pour the first part of the soil sample into the Miller Soil Box, level the surface and compact it to the required height, then roughen the surface, then pour the second part of the soil sample, level the surface again and compact it to the required height;

[0124] Step 2.8, through the above steps, remolded soil samples with specified moisture content, NaCl concentration and density can be accurately prepared. The experiment was designed to measure the corresponding resistivity of 9 soil samples with different moisture contents. In addition, for soil samples with the same moisture content, the light layered compaction method was used to prepare samples with 5 different densities (70%, 80%, 90%, 95%, 100%) and 5 different NaCl concentrations (0%, 2%, 4%, 6%, 8%);

[0125] Step 2.9: Repeat the resistivity measurement of each soil sample three times, and take the arithmetic mean as the final measurement result. Based on the control variable method, the resistivity variation law of the soil under different soil ion concentrations, different water contents, and different densities is studied in turn, and the relationship between resistivity and different factors is plotted (see Figure 3 to Figure 6 ), obtain the quantitative relationship curve between resistivity and various influencing factors, and observe the characteristics of the curve to assist analysis;

[0126] Step 3, based on the quantitative relationship curve between resistivity and various influencing factors, a loess resistivity calculation model of the detection area is fitted;

[0127] Step 3.1, according to Figure 3 to Figure 6 The results show that the single factor (NaCl concentration or water content or compaction) and the soil resistivity are in accordance with the power function relationship. Considering the actual silt dam project, it is judged that except for some parts located in saline-alkali land, the soil resistivity of the rest of the project is mostly affected by water content and compaction. The NaCl concentration factor can be removed to help improve the fitting accuracy and quality, and the relationship surface between the influencing factors of water content, compaction and soil resistivity can be drawn (see Figure 7 ), observe the change characteristics between the two and resistivity to assist understanding;

[0128] Step 3.2, the generalized Archie formula is selected to fit the calculation model between soil resistivity and influencing factors. According to the statistical analysis of the test data, the regional clay resistivity model of northern Shaanxi, China is obtained:

[0129] ρ F =(2.39×10 7 )φ -2.23 ω -1.14 +(φ×ω) -3.49 (5)

[0130] The multiple correlation coefficient is 0.924, which is highly correlated.

[0131] Step 4: After the on-site inspection and instrument self-test preparation, a DUK-2A high-density electrical measurement system, which mainly consists of a multi-channel electrode converter and a DZD-6A multi-function DC electrical instrument, is used to conduct non-destructive testing field tests on the inspection area to obtain an apparent resistivity image of the area; specifically:

[0132] Step 4.1: On-site inspection of the project area to be tested, including preliminary leakage inspection and line layout, see Figure 8 (5 survey lines were laid out, one on the upstream low dam slope, one on the upstream high dam slope, one on the dam top, and two on the downstream horse trail) and parameter selection, and then the universal Wenner device and the Scheib profile device mode were selected to carry out non-destructive testing field tests in the test area. High-density electrical data acquisition work was carried out;

[0133] Step 4.2, using the Lizheng high-density software to perform data conversion, data preprocessing and terrain correction on the collected data, and finally invert the calculation to obtain the apparent resistivity image of the field test, see Figures 9 to 13 ;

[0134] Step 5: Combine indoor and outdoor tests to conduct qualitative and quantitative dual interpretation of the on-site detection results, so as to conduct a comprehensive analysis of the leakage situation in the detected area; specifically:

[0135] Step 5.1, using the soil resistivity calculation model of the indoor test, the resistivity tomography results obtained from the field detection are converted into intuitive water content values ​​to assist in the quantitative interpretation of the field test, see Table 5;

[0136] Table 5 Nondestructive testing calculation results

[0137]

[0138] Step 5.2, conduct a comprehensive analysis of the leakage situation in the detected area in combination with the resistivity tomography results of the on-site detection, namely:

[0139] (1) Survey lines 1 and 2 are respectively laid out on the upstream low dam slope and upstream high dam slope of the dam body. They are significantly affected by the reservoir water level. After water storage, the dam body infiltration line at the upstream position is higher and the soil is rich in water, resulting in a small resistivity value in the detection area. The calculated moisture content at the locations of survey lines 1 and 2 is greater than the natural moisture content of the silty loam of the dam body of 15%. In addition, in the apparent resistivity inversion results of survey lines 1 and 2, there are large-scale low-resistance anomaly areas, which have formed a closed low-resistance circle, which is speculated to be the main source of dam body leakage.

[0140] (2) Survey lines 3 and 4 are respectively laid on the dam crest and the 100m downstream horse track, both located in the middle of the dam body. The impact of the upstream reservoir water on them is weakened, the dam body infiltration line is lowered, and the soil moisture content is relatively small. Therefore, the overall resistivity value in the detection area is relatively large. However, according to the attached Figure 8 The apparent resistivity inversion results show that there are small low-resistance anomaly areas on both sides of the bottom of the image. It can be found from Table 10 that the soil moisture content calculated by survey lines 3 and 4 is greater than the maximum moisture content of 35% used in the indoor test, which is much greater than the natural moisture content of 15% of the silty loam in the dam body. At this moisture content, the proportion of solid particles in the soil is reduced, the connection between water is enhanced, the soil conduction is mainly carried out through the liquid phase, and the soil resistivity is almost unaffected by the compaction degree. Based on this, it is judged that there are leakage areas on both sides of the bottom of the section measured by survey lines 3 and 4, and they are connected with the leakage areas of survey lines 1 and 2, and develop into leakage channels.

[0141] (3) Survey line 5 is laid on the horse road 90m downstream, and the starting position of the survey line is close to the water discharge structure on the right bank of the dam. The water discharge structure of Dongmengou silt dam is mainly composed of brick-concrete graded horizontal pipes and stone water culverts. The horizontal pipe discharge flow is 0.5m 3 / s, and an energy dissipation pool is set at the end. After dissipating energy, the water flows out from the water conveyance culvert buried under the dam. The culvert is buried in a direction that is basically perpendicular to the axis of the dam. Since the water discharge structure of the dam was not professionally planned and designed, the project was simple. As a result, after years of operation, the horizontal pipes and stone culverts on the right bank were seriously damaged, causing some water to seep into the nearby soil and even siltation inside the dam. Therefore, the left area of ​​the apparent resistivity inversion results of survey lines 3 to 5 showed low resistance anomalies, as shown in the attached figure. Figure 8 According to the calculation results in Table 10, the moisture content of this measuring line is between 34% and 47%, which is significantly higher than the natural moisture content of 15% of the silty loam in the dam body. It is speculated that this is related to leakage in the upstream.

[0142] In summary, combined with comprehensive analysis of on-site investigation, ① the water discharge structure on the right bank of the Dongmengou silt dam is aging and damaged, causing leakage in the dam body on the right bank. Figure 8 ① The low-resistance anomaly is found in the left area of ​​the measurement section; ② Affected by the upstream reservoir water, a leakage channel is developed along the path from the left bank to the downstream foot of the slope, causing leakage of the left bank dam body, corresponding to the low-resistance anomaly in the right area of ​​the measurement section in the attached figure; ③ According to the apparent resistivity inversion results, it is speculated that there is seepage recharge between the low-resistance anomaly areas of the five measuring lines, and a leakage channel is formed in the dam body near the left bank of the silt dam, and the water eventually overflows at the downstream foot of the slope. The inferred results are consistent with the location of the downstream leakage point found during the on-site inspection, which to a certain extent illustrates the authenticity of the inversion results.

[0143] Step 5.3, use SketchUp to draw a 3D model of the dam body, select the apparent resistivity image in the Speicherstadt profile device mode and place it at the actual detection position, and draw a schematic diagram of the leakage channel, see Fig.14 , and combined with the results of 5.2 to determine the location of leakage hazards, see Table 6.

[0144] Table 6 Location of leakage hazards on the left bank of Dongmengou silt dam

[0145]

[0146]

[0147] It can be seen from Table 6 that the low-resistance anomaly areas obtained by inversion calculation of different survey lines have certain differences in pile numbers and elevations, but their plane positions are basically corresponding, and the central position of the low-resistance anomaly area decreases successively in spatial elevation, proving that the leakage of the silt dam is very likely to be natural infiltration.

[0148] The results show that the high-density resistivity tomography method has good applicability and feasibility in the non-destructive detection of leakage hazards in silt dams. Combined with the indoor test of the resistivity characteristics of the soil in the silt dam, it can quickly determine the occurrence, burial depth and scale of the abnormal body, and has significant advantages such as non-destructive, high detection efficiency, and rich data information. Through this example, it is strongly proved that the present invention can effectively assist in the quantitative interpretation of high-density electrical method.

[0149] Example 2

[0150] The high-density electrical quantitative interpretation method based on the soil resistivity calculation model is characterized by:

[0151] Step 1: measure the physical properties of the sampled soil in the detection area, conduct orthogonal tests on the main influencing factors of the soil resistivity, and analyze the primary and secondary factors affecting the resistivity change;

[0152] Step 1 is as follows:

[0153] Step 1.1, conduct various geotechnical tests on the original soil samples to determine the natural moisture content / %, optimal moisture content / %, maximum dry density, plastic limit / %, and liquid limit / % of the samples, in preparation for the calculation and analysis of the tests;

[0154] Step 1.2, soil ion concentration, moisture content, soil compaction and temperature are selected as four factors, each factor considers three levels and selects three representative low, medium and high contents according to the experimental objectives, and designs and conducts orthogonal experiments;

[0155] Step 1.3, based on the orthogonal test results, obtain the data sum value K of different factors at different levels, the average value Kavg of the K value and the range value R, use Kavg to draw the factor average value graph, observe its decline rate to assist analysis, and use the range R to determine the primary and secondary order of the influence of the four factors on soil resistivity.

[0156] Step 2, select three factors with the largest influence to conduct quantitative tests, and determine the quantitative relationship between the resistivity of the soil sample and the influencing factors;

[0157] Step 3: Based on the quantitative relationship between resistivity and various influencing factors, a soil resistivity calculation model of the detection area is fitted;

[0158] Step 4: Conduct nondestructive testing field tests on the detection area to obtain an apparent resistivity image of the area;

[0159] Step 5: Combine indoor and field tests to perform both qualitative and quantitative interpretation of the on-site detection results, so as to conduct a comprehensive analysis of the leakage situation in the detected area.

[0160] Example 3

[0161] The high-density electrical quantitative interpretation method based on the soil resistivity calculation model is as follows:

[0162] Step 1: measure the physical properties of the sampled soil in the detection area, conduct orthogonal tests on the main influencing factors of the soil resistivity, and analyze the primary and secondary factors affecting the resistivity change;

[0163] Step 2, select three factors with the largest influence to conduct quantitative tests, and determine the quantitative relationship between the resistivity of the soil sample and the influencing factors;

[0164] Step 3: Based on the quantitative relationship between resistivity and various influencing factors, a soil resistivity calculation model of the detection area is fitted;

[0165] Step 4: Conduct nondestructive testing field tests on the detection area to obtain an apparent resistivity image of the area;

[0166] Step 5: Combine indoor and field tests to perform both qualitative and quantitative interpretation of the on-site detection results, so as to conduct a comprehensive analysis of the leakage situation in the detected area.

Claims

1. A high-density electrical quantitative interpretation method based on soil resistivity calculation model, characterized in that: Specifically: Step 1: measure the physical properties of the sampled soil in the detection area, conduct orthogonal tests on the main influencing factors of the soil resistivity, and analyze the primary and secondary factors affecting the resistivity change; Step 2, select three factors with the largest influence to conduct quantitative tests, and determine the quantitative relationship between the resistivity of the soil sample and the influencing factors; Step 3: Based on the quantitative relationship between resistivity and various influencing factors, a soil resistivity calculation model of the detection area is fitted; Step 4: Conduct nondestructive testing field tests on the detection area to obtain an apparent resistivity image of the area; Step 5: Combine indoor and field tests to perform both qualitative and quantitative interpretation of the on-site detection results, so as to conduct a comprehensive analysis of the leakage situation in the detected area.

2. The high-density electrical quantity interpretation method based on soil resistivity calculation model according to claim 1 is characterized in that: Step 1 is as follows: Step 1.1, conduct various geotechnical tests on the original soil samples to determine the natural moisture content / %, optimal moisture content / %, maximum dry density, plastic limit / %, and liquid limit / % of the samples, in preparation for the calculation and analysis of the tests; Step 1.2, soil ion concentration, moisture content, soil compaction and temperature are selected as four factors, three levels of each factor are considered and three representative low, medium and high contents are selected according to the experimental objectives, and an orthogonal experiment is designed and conducted; Step 1.3, based on the orthogonal test results, obtain the data sum value K of different factors at different levels, the average value Kavg of the K value and the range value R, use Kavg to draw the factor average value graph, observe its decline rate to assist analysis, and use the range R to determine the primary and secondary order of the influence of the four factors on soil resistivity.

3. The high-density electrical quantity interpretation method based on soil resistivity calculation model according to claim 2 is characterized in that: Step 2 is as follows: Step 2.2, prepare M portions of B water samples corresponding to the water sample B standard at n different moisture contents, and obtain n*M portions of B water samples; calculate the mass of ionic substances corresponding to M different soil ion concentrations at n different moisture contents according to the following formula (2), prepare n*M portions of corresponding ionic substances according to the calculation results, and add the ionic substances to the n*M portions of B water samples respectively, to prepare samples C with M different soil ion concentrations at n different moisture contents, a total of n*M portions; Where: m N The mass of ionic substances required to be added to the soil sample; m ω is the required amount of water; N is the soil ion concentration; Step 2.3, calculate the internal volume of the Miller Soil Box device used in the test, and weigh the mass of soil samples corresponding to M different compaction degrees at n different moisture contents according to the following formula (3), and prepare corresponding n*M soil samples according to the calculated results; m'=ρ dmax P i V(1+0.01ω0) (3) Where: m' is the required amount of soil sample; ρ dmax is the maximum dry density; P i is the density; V is the internal volume of the Miller Soil Box; Step 2.4, prepare M water samples according to the water sample A standard at n different moisture contents, for a total of n*M samples, use a spray pot to take water sample A respectively, spray the water sample evenly on the soil prepared in 2.3, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours; Step 2.5, randomly select a soil sample prepared in 2.3, make n*M copies, record as soil sample D, use a spray bottle to take sample C respectively, spray the water sample evenly on the prepared soil material D, mix thoroughly and put it into a closed container and let it stand for 24 hours, mix the soil sample thoroughly after standing for 24 hours, take a certain amount of soil sample to determine its moisture content, if it cannot meet the test requirements, add water sample C to the soil sample or air dry it to lose water, mix it again and let it stand in a closed container for another 24 hours; Step 2.6, repeat steps 2.4 and 2.5 until the prepared soil sample reaches the n kinds of moisture content, M kinds of different densities and M kinds of different soil ion concentrations required by the test, and the difference between the actual and the preset values ​​should be controlled within the range of ±1%; Step 2.7, prepare the final sample by light layered compaction method; divide the soil sample weighed in step 2.6 into 2 equal parts, first pour the first part of the soil sample into the Miller Soil Box, level the surface and compact it to the required height, then roughen the surface, then pour the second part of the soil sample, level the surface again and compact it to the required height; Step 2.8, through the above steps, remolded soil samples with specified moisture content, soil ion concentration and density can be accurately prepared, with a total of 2*n*M parts; Step 2.9, the resistivity of each soil sample is measured 2 to 3 times, and the arithmetic mean is taken as the final measurement result. Based on the control variable method, the resistivity change law of the soil under different soil ion concentrations, different water contents, and different densities is studied in turn.

4. The high-density electrical quantity interpretation method based on soil resistivity calculation model according to claim 3 is characterized in that: Step 3 is as follows: Step 3.1: Determine the relationship between the influencing factors and the resistivity of the soil sample based on the test results in 2.9; and consider whether such influence exists in the actual project and remove 1 to 2 factors appropriately; Step 3.2, choose to use the generalized Archie formula to fit the soil resistivity and the calculation model between the influencing factors determined in 3.1, that is, the soil resistivity calculation model, the expression is as follows: r F =Kφ -m oh -n +f(φ,ω) (4) Where: F is the resistivity of soil sample, Ω·m; φ is the influencing factor of 1%; ω is the influencing factor of 2%; K, m, n are soil parameters; f(φ,ω) is an additional function.

5. The high-density electrical quantity interpretation method based on soil resistivity calculation model according to claim 3 is characterized in that: In step 4, a nondestructive testing field test is carried out on the detection area using the DUK-2A high-density electrical measurement system to obtain an apparent resistivity image of the area.

6. The high-density electrical quantitative interpretation method based on soil resistivity calculation model according to claim 3 is characterized in that: Step 5 is as follows: Step 5.1, using the soil resistivity calculation model of indoor test 3.2, convert the apparent resistivity result obtained by field detection in step 4 into an intuitive water content value; Step 5.2, combine the indoor test, field test and the soil sample results obtained in step 1.1 to conduct a comprehensive analysis of the leakage situation in the tested area, specifically: if the moisture content of the soil sample is lower than the natural moisture content, it means there is no leakage; if the moisture content of the soil sample exceeds the natural moisture content and is less than the liquid limit, there may be leakage, and then combine the on-site investigation to confirm whether there is leakage; if the moisture content of the soil sample exceeds the liquid limit, there is leakage; Step 5.3: Use SketchUp to draw a three-dimensional model of the dam body, select the apparent resistivity image and place it at the actual detection location, draw a schematic diagram of the leakage channel, and determine the location of the leakage risk based on the results of Step 5.2.

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