River terrace rapid comparison method based on gravel hardness measurement

Abstract

The invention discloses a river terrace rapid comparison method based on gravel hardness measurement. The method comprises the following steps: carrying out gravel sample collection along a river terrace according to a preset sampling grid; measuring the hardness of the collected gravel sample by using a springback hammer; establishing a gravel weathering index model, and calculating a comprehensive weathering index of each terrace based on the model; grading the river terrace according to the weathering index; the method further comprises a correction mechanism based on landform and age measurement data and a complete reliability evaluation system. The method is simple to operate and low in cost, can quickly realize river terrace identification and comparison, and has important theoretical value and practical significance.

Description

Technical Field

[0001] The invention belongs to the technical field of terrace measurement, and in particular relates to a rapid comparison method of river terraces based on gravel hardness measurement. Background Art

[0002] River terraces are important geomorphic units. Terrace sediments record the climate and environmental information of the period of their formation. Terraces formed in different periods can reflect the response of rivers to climate change. The material composition of terrace sediments can indicate changes in climatic conditions in the source area. The development sequence of terraces reflects the river incision process and the evolutionary history of the valley. At the same time, the formation, distribution and preservation characteristics of river terraces can indicate the nature and intensity of regional tectonic activities. The deformation, faulting and elevation changes of terraces can reflect the characteristics of neotectonic movements. The history of regional tectonic uplift can be reconstructed through terrace sequence analysis. Its research has important scientific significance and practical value. In addition, river terraces are important industrial and agricultural production, living and engineering construction sites. The classification, comparison and stability assessment of terraces are of great significance to engineering safety.

[0003] However, there are some problems with the existing river terrace research methods. The traditional morphological comparison method mainly relies on geomorphological features and relative heights for comparison, which is greatly affected by terrain undulations and the degree of terrace preservation integrity and lacks objective quantitative indicators. The sediment analysis method requires a large amount of field sampling and indoor experiments, with a long analysis cycle, high cost, and the results are easily affected by local factors. The dating method has high test sample requirements, sampling is difficult, and the testing cost is expensive. Not all terraces have materials suitable for dating, and the dating method has a certain lag. In addition, the existing rapid identification methods generally lack systematic quantitative standards, are highly subjective, and have poor repeatability, making it difficult to establish regional comparison standards.

[0004] Therefore, there is an urgent need to establish a rapid, objective and quantifiable river terrace comparison method. Summary of the invention

[0005] The purpose of the present invention is to provide a rapid river terrace comparison method based on gravel hardness measurement, so as to achieve the purpose of rapid, objective and quantifiable river terrace comparison; The specific technical solutions are as follows: The present invention provides a rapid comparison method for river terraces based on gravel hardness measurement, the method comprising the following steps: Step 1: Collect gravel samples at sampling points along the river terrace according to the preset sampling grid.

[0006] Furthermore, the preset sampling grid is a 10m×10m grid divided along the river terrace, and at most one gravel sample is collected in each grid; the sampling interval of the preset sampling grid is: sampling once every 5-10 grids in the main flow direction, and sampling once every 2-5 grids perpendicular to the main flow direction; sampling at each sampling point Gravel samples, , the particle size range of the gravel sample is 2-10 cm.

[0007] Furthermore, the gravel samples should be surface treated before measurement, including: using a brush to remove loose materials on the sample surface, rinsing the sample surface with distilled water and then air-drying it for 24 hours.

[0008] Step 2: Use a rebound hammer to measure the hardness of each gravel sample collected to obtain the rebound value of each sample.

[0009] Furthermore, the hardness measurement method comprises the following steps: Step S21, fixing the gravel sample on a flat test table.

[0010] Step S22, using a rebound hammer to Rebound measurement, , record each rebound value .

[0011] Step S23, calculating the average rebound value after removing the maximum and minimum values .

[0012] Step 3: Establish a gravel weathering index model, and calculate the comprehensive weathering index of each terrace based on the gravel weathering index model.

[0013] Furthermore, the mathematical expression of the gravel weathering index model is: ;in, is the comprehensive weathering index of gravel; For the The average rebound value of the gravel samples, is the standard rebound value of fresh unweathered gravel, is the average thickness of the weathered layer on the gravel surface, in mm; is the reference thickness, which is 1mm; is the percentage of weathering products on the gravel surface; the weathering product content The determination method is as follows: select three 1 cm × 1 cm test areas on the gravel surface; use a digital microscope to photograph the test areas; use image analysis software to calculate the percentage of weathering product coverage area; take the average value of the three test areas as ; is the reference content, with a value of 1%; , , is the weight coefficient, symbol It means multiplying both sides; ; ; .

[0014] is the coefficient of variation of the rebound value; is the coefficient of variation of the weathering layer thickness; is the coefficient of variation of weathering product content, .

[0015] Step 4: classify the river terraces according to the quantitative calculation results of the gravel comprehensive weathering index.

[0016] Furthermore, the river terraces are divided into five levels, wherein the first level terraces are: ; Secondary terrace: ; Third terrace: ; Fourth terrace: ; Fifth terrace: .

[0017] Furthermore, the average thickness of the weathered layer on the gravel surface is The calculation method is: ;in, is the number of measurement points, ; For the The thickness of the weathered layer at each measuring point is measured using a vernier caliper.

[0018] Furthermore, the gravel weathering index model in step 3 further includes the step of correcting the gravel comprehensive weathering index using geomorphology and / or dating data; Furthermore, when the relative height data of a terrace is obtained, the following formula is used to correct the gravel comprehensive weathering index before classifying the river terrace: ;in, is the modified gravel comprehensive weathering index, is the relative height of the terrace, in m; is the reference height, which is 10m; is the topography correction factor, ; Topography correction factor The calculation formula is: ; is the terrace slope, The reference slope is 5 degrees.

[0019] Furthermore, when the dating data of a terrace is obtained, the corresponding relationship between the weathering index and the age is established to correct the gravel comprehensive weathering index: ,in , They are the regional first fitting coefficient and the second fitting coefficient, respectively, and their calculation method is: , ; is the age of the sample of known age, is the corresponding gravel comprehensive weathering index, is the initial estimated age, is the average weathering index of known samples, is the number of samples with known age.

[0020] Furthermore, the rapid comparison method also includes a reliability assessment step: calculating the coefficient of variation of each terrace sample : ; is the sample standard deviation, is the sample mean, when When When , the number of samples needs to be increased; when The sampling point needs to be reselected.

[0021] Furthermore, in step S23, the average rebound value is calculated after removing the maximum value and the minimum value. Finally, there is also a step to correct the rebound value based on environmental influences: measuring the ambient temperature (℃) and relative humidity (%); Calculate the environmental correction factor: , multiply the measured rebound value by Make corrections.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a rapid comparison method for river terraces based on gravel hardness measurement. Through systematic gravel sample collection and standardized measurement process, rapid, objective and quantifiable river terrace research is achieved. Compared with traditional methods, the present invention has the advantages of simple operation, low cost and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a rapid river terrace comparison method based on gravel hardness measurement. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described implementation mode is a part of the present invention, not all implementation modes. Based on the implementation modes of the present invention, all other implementation modes obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that gravel, as a common component in river terraces, has a close relationship between its weathering degree and the formation age of the terraces. Through systematic research on the weathering characteristics of gravel and the establishment of a standardized measurement and evaluation system, a new technical approach can be provided for the rapid comparison of river terraces. The present invention is based on this idea, using portable equipment to conduct on-site measurement of the hardness and weathering characteristics of gravel, and combining mathematical models to establish quantitative evaluation standards, which can quickly realize the identification and comparison of river terraces, and has important theoretical value and practical significance.

[0026] like Figure 1 FIG. 1 is a flow chart of a rapid river terrace comparison method based on gravel hardness measurement according to the present invention, and the method comprises the following steps: Step 1: Collect gravel samples at sampling points along the river terrace according to the preset sampling grid.

[0027] The preset sampling grid is a 10m×10m grid divided along the river terrace, and a maximum of one gravel sample is collected in each grid. The sampling spacing of the preset sampling grid is: sampling once every 5-10 grids in the main flow direction, and sampling once every 2-5 grids perpendicular to the main flow direction; taking a certain study area as an example, the area has developed a complete terrace sequence with an area of ​​about 2km². After dividing into 10m×10m grids, a sampling point is set every 50-100m (5-10 grids) in the main flow direction, and a sampling point is set every 20-50m (2-5 grids) perpendicular to the main flow direction. Finally, 32 valid sampling points were determined; this sampling strategy not only ensures the representativeness of the data, but also avoids the increase in workload caused by over-dense sampling; each sampling point collects Gravel samples, , the particle size range of the gravel sample is 2-10 cm.

[0028] Before measurement, the gravel sample should be treated on the surface, including: using a brush to remove loose materials on the sample surface, rinsing the sample surface with distilled water and then air-drying it for 24 hours; in field work, it was found that the treatment of the gravel surface had a significant impact on the measurement results. Comparative tests showed that the coefficient of variation of the rebound value of the sample after brush cleaning and distilled water rinsing was reduced by an average of 15%, and the repeatability of the measurement was significantly improved. It is recommended to choose sunny weather for field work to avoid the sample being affected by moisture and affecting the measurement results.

[0029] In practical applications, the method of the present invention has been verified in a number of typical river areas; for example, in a study of a tributary in the middle reaches of a river, the method was used to quickly identify and compare the five-level terraces within a 20km river section; the results showed that the method could complete all field work within 2-3 days, saving about 70% of the time compared to traditional methods, and the results had a good correspondence with the existing chronological data.

[0030] Step 2: Use a rebound hammer to measure the hardness of each gravel sample collected to obtain the rebound value of each sample.

[0031] The hardness measuring method comprises the following steps: Step S21, fixing the gravel sample on a flat test table.

[0032] Step S22, using a rebound hammer to Rebound measurement, , record each rebound value .

[0033] Step S23, calculating the average rebound value after removing the maximum and minimum values .

[0034] Tests show that the measurement results are most stable when the number of rebound measurements is m = 20. To ensure the accuracy of the measurement, the surface of the gravel should be relatively flat for measurement, the distance between the measuring points should be no less than 1 cm, and obvious cracks and uneven areas should be avoided.

[0035] Step 3: Establish a gravel weathering index model, and calculate the comprehensive weathering index of each terrace based on the gravel weathering index model.

[0036] The mathematical expression of the gravel weathering index model is: ;in, is the comprehensive weathering index of gravel; For the The average rebound value of the gravel samples, is the standard rebound value of fresh unweathered gravel, is the average thickness of the weathered layer on the gravel surface, in mm; is the reference thickness, which is 1mm; is the percentage of weathering products on the gravel surface; the weathering product content The determination method is as follows: select three 1 cm × 1 cm test areas on the gravel surface; use a digital microscope to photograph the test areas; use image analysis software to calculate the percentage of weathering product coverage area; take the average value of the three test areas as ; is the reference content, with a value of 1%; , , is the weight coefficient, symbol It means multiplying both sides; ; ; .

[0037] is the coefficient of variation of the rebound value; is the coefficient of variation of the weathering layer thickness; is the coefficient of variation of weathering product content, .

[0038] Through the analysis of a large amount of experimental data, it was found that the model showed good applicability in gravels of different lithologies; for example, the test results of granite gravel showed that the weathering index was significantly negatively correlated with the compressive strength measured in the laboratory (correlation coefficient R²=0.87), which confirmed the scientific nature of the model.

[0039] Step 4: classify the river terraces according to the quantitative calculation results of the gravel comprehensive weathering index.

[0040] The river terraces are divided into five levels, among which the first level terrace is: ; Secondary terrace: ; Third terrace: ; Fourth terrace: ; Fifth terrace: .

[0041] The average thickness of the weathered layer on the gravel surface The calculation method is: ;in, is the number of measurement points, ; For the The thickness of the weathered layer at each measuring point is measured using a vernier caliper.

[0042] The gravel weathering index model in step 3 further includes the step of correcting the gravel comprehensive weathering index using geomorphology and / or dating data; When the relative height data of a terrace is obtained, the following formula is used to correct the gravel comprehensive weathering index before classifying the river terrace: ;in, is the modified gravel comprehensive weathering index, is the relative height of the terrace, in m; is the reference height, which is 10m; is the topography correction factor, ; Topography correction factor The calculation formula is: ; is the terrace slope, The reference slope is 5 degrees.

[0043] Taking a river terrace as an example, the relative height of the terrace is 25m and the slope is 8°. Applying the geomorphic correction formula, λ=0.16 is calculated, and the corrected weathering index is increased from the original 0.75 to 0.82, which is more in line with the actual age characteristics of the terrace; this shows that the geomorphic correction mechanism can effectively improve the accuracy of the evaluation results.

[0044] When the dating data of a terrace is obtained, the corresponding relationship between weathering index and age is established to correct the gravel comprehensive weathering index: ,in , They are the regional first fitting coefficient and the second fitting coefficient, respectively, and their calculation method is: , ; is the age of the sample of known age, is the corresponding gravel comprehensive weathering index, is the initial estimated age, is the average weathering index of known samples, is the number of samples with known age.

[0045] In a certain study area, 12 terrace samples of known age (age range 5-200ka) were collected, and the regional coefficients A=12.5ka and B=2.3 were obtained through fitting. These parameters were used to estimate the terraces of unknown age, and the deviation between the results and the OSL dating data was within 15%, proving that this method has good practical value.

[0046] The rapid comparison method also includes a reliability assessment step: calculating the coefficient of variation of each terrace sample : ; is the sample standard deviation, is the sample mean, when When When , the number of samples needs to be increased; when The sampling point needs to be reselected.

[0047] In step S23, the average rebound value is calculated after removing the maximum value and the minimum value. Finally, it also includes the step of correcting the rebound value based on environmental influences; environmental factors have a significant impact on the measurement results. For example, when the temperature rises from 20°C to 30°C, the uncorrected rebound value increases by an average of about 1%; when the relative humidity decreases from 60% to 40%, the uncorrected rebound value increases by an average of about 0.4%; therefore, environmental correction is an important step to ensure measurement accuracy; measuring the ambient temperature (℃) and relative humidity (%); Calculate the environmental correction factor: , multiply the measured rebound value by Make corrections.

[0048] Coefficient of variation of rebound value Calculation: For each sampling point gravel samples, calculate the average rebound value and standard deviation : ; ; .

[0049] Calculation of the coefficient of variation CVD of weathering layer thickness: Select 5 gravel samples at each sampling point, measure the weathering layer thickness of k points (k ≥ 5) for each sample; calculate the average thickness and standard deviation : ; ; ;in, For the Sample No. The thickness of the weathering layer at each measuring point.

[0050] Calculation of coefficient of variation CVP of weathering product content: Select 5 gravel samples for each sampling point, measure the weathering product content of 3 areas in each sample; calculate the average content and standard deviation : ; ; ;in For the Sample No. The content of weathering products in each test area.

[0051] The preprocessing requirements for sample data include: performing outlier tests on each set of data and eliminating data with obvious deviations; when a measurement value deviates from the mean by more than 3 times the standard deviation, the data should be remeasured or eliminated; and the calculation of each coefficient of variation requires at least 5 valid sample data.

[0052] If any coefficient of variation CV>50%, the number of measurements of this parameter needs to be increased. If the coefficient of variation is still>50% after increasing the number of measurements, the sampling points should be reselected. All numerical calculations should retain 3 significant digits.

[0053] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rapid comparison method for river terraces based on gravel hardness measurement, characterized in that: The method comprises the following steps: Step 1: Collect gravel samples at sampling points along the river terrace according to a preset sampling grid; The preset sampling grid is a 10m×10m grid divided along the river terrace, and at most one gravel sample is collected in each grid; Each sampling point collects gravel samples, , the particle size range of the gravel sample is 2-10 cm; Step 2: Use a rebound hammer to measure the hardness of each gravel sample collected to obtain the rebound value of each sample; The hardness measuring method comprises the following steps: Step S21, fixing the gravel sample on a flat test table; Step S22, using a rebound hammer to Rebound measurement, , record each rebound value ; Step S23, calculating the average rebound value after removing the maximum and minimum values ; Step 3: Establishing a gravel weathering index model, and calculating the comprehensive weathering index of each terrace based on the gravel weathering index model; The mathematical expression of the gravel weathering index model is: ;in, is the comprehensive weathering index of gravel; For the The average rebound value of the gravel samples, is the standard rebound value of fresh unweathered gravel, is the average thickness of the weathered layer on the gravel surface, in mm; is the reference thickness, which is 1mm; is the percentage of weathering products on the gravel surface; is the reference content, with a value of 1%; , , is the weight coefficient, symbol It means multiplying both sides; ； ； ； is the coefficient of variation of the rebound value; is the coefficient of variation of the weathering layer thickness; is the coefficient of variation of weathering product content, ; Step 4, classifying the river terraces according to the quantitative calculation results of the gravel comprehensive weathering index; The river terraces are divided into five levels, among which the first level terrace is: ; Secondary terrace: ; Third terrace: ; Fourth terrace: ; Fifth terrace: .

2. A rapid river terrace comparison method based on gravel hardness measurement according to claim 1, characterized in that: The sampling interval of the preset sampling grid is: sampling once every 5-10 grids in the main flow direction, and sampling once every 2-5 grids perpendicular to the main flow direction.

3. A rapid river terrace comparison method based on gravel hardness measurement according to claim 2, characterized in that: The average thickness of the weathered layer on the gravel surface The calculation method is: ;in, is the number of measurement points, ; For the The thickness of the weathered layer at each measuring point is measured using a vernier caliper.

4. A rapid river terrace comparison method based on gravel hardness measurement according to claim 3, characterized in that: The gravel weathering index model in step 3 further includes the step of correcting the gravel comprehensive weathering index using geomorphology and / or dating data; When the relative height data of a terrace is obtained, the following formula is used to correct the gravel comprehensive weathering index before classifying the river terrace: ;in, is the modified gravel comprehensive weathering index, is the relative height of the terrace, in m; is the reference height, which is 10m; is the topography correction factor, ; When the dating data of a terrace is obtained, the corresponding relationship between weathering index and age is established to correct the gravel comprehensive weathering index: ,in , They are the regional first fitting coefficient and the second fitting coefficient, respectively, and their calculation method is: ， ； is the age of the sample of known age, is the corresponding gravel comprehensive weathering index, is the initial estimated age, is the average weathering index of known samples, is the number of samples with known age.

5. A rapid river terrace comparison method based on gravel hardness measurement according to claim 4, characterized in that: The rapid comparison method also includes a reliability assessment step; Calculate the coefficient of variation for each terrace sample : ; is the sample standard deviation, is the sample mean, when When When , the number of samples needs to be increased; when The sampling point needs to be reselected.

6. A rapid river terrace comparison method based on gravel hardness measurement according to claim 5, characterized in that: The gravel sample should be surface treated before measurement, including: using a brush to remove loose materials on the sample surface, rinsing the sample surface with distilled water and then air-drying it for 24 hours.

7. A rapid river terrace comparison method based on gravel hardness measurement according to claim 5, characterized in that: The weathering product content The determination method is as follows: select three 1 cm × 1 cm test areas on the gravel surface; use a digital microscope to photograph the test areas; use image analysis software to calculate the percentage of weathering product coverage area; take the average value of the three test areas as .

8. A rapid river terrace comparison method based on gravel hardness measurement according to claim 5, characterized in that: Terrain correction factor The calculation formula is: ; is the terrace slope, The reference slope is 5 degrees.

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