A method for scaling the soil particle size distribution of a damming body physical model

Abstract

The application discloses a method for scaling the particle size distribution of a soil body of a dammed body physical model, and belongs to the technical field of soil tests. i 50% of the particle size is linearly scaled, P i ≤50% of the particle size is nonlinearly scaled, which can meet the requirements of the dammed body physical model test, ensure the continuity of the particle size distribution curve after scaling, and has strong operability for actual work. The method solves the problems of complicated calculation of the existing scaling methods and the inability to quantitatively describe the particle size distribution after scaling and the original particle size distribution.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical testing, and in particular relates to a particle grading scaling method for a physical model of a dam body. Background Art

[0002] The soil is composed of soil particles of different sizes. The size and composition of soil particles are called particle grading. Particle grading has a very important influence on the strength, deformation and permeability characteristics of the soil. The particle grading of soil is mainly determined by particle analysis tests. According to the test results, it is generally represented by a cumulative particle size curve. The cumulative particle size curve is also called a grading curve. Its horizontal axis is the particle size, and the vertical axis is the cumulative percentage of soil mass smaller than a certain particle size (abbreviated as mass percentage), which is represented by a single logarithmic coordinate. The maximum scale of the landslide naturally formed by geological action can reach hundreds of millions to billions of cubic meters, and the maximum particle size of its particles can generally reach 2000mm to 5000mm. Indoor tests cannot be carried out according to the prototype. Therefore, when scaling the scale, storage capacity, flow rate, etc. of the landslide, the particle grading of the landslide must be scaled simultaneously, and the scaled gradation is used as the material gradation for the physical model of the landslide. The current scaling methods include elimination method, similar grading method, equal amount replacement method and mixing method. The above methods have three obvious defects:

[0003] (1) When calculating the percentage of each particle size after scaling according to the scaling rule, the process is sometimes cumbersome. For example, the mixing method is a comprehensive application of the similar gradation method and the equal substitution method. In order to obtain a satisfactory fine particle content, it is often necessary to first select several groups of different similar gradation scaling ratios, and then use the equal substitution method to perform trial calculations to obtain the final test gradation.

[0004] (2) The scaled gradation and the original gradation are currently expressed by the particle size content or gradation curve. The internal relationship or difference between them in terms of "value" is difficult to describe quantitatively, making it impossible to conduct a comprehensive and systematic study on the scaled effect of coarse aggregates.

[0005] (3) The particle scaling of geotechnical tests is more concerned with the similarity of material strength, while the particle scaling of the physical model of landslide dam failure needs to consider the similarity of erosion resistance. Typical landslide dams are generally non-cohesive soils, and the clay content has a great influence on the erosion characteristics of the soil and the development mechanism of erosion at the breach. The existing scaling method cannot be directly applied to the physical model of landslide dam failure. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention aims to provide a method for scaling down the particle gradation of soil in a physical model of a landslide dam. This method is used to scale down the particle gradation of soil in a natural state of the landslide dam according to an appropriate ratio to meet the requirements of the physical model test of the landslide dam, thereby solving the problems of cumbersome calculations in the existing scaling methods and the inability to quantitatively describe the scaled gradation and the original gradation.

[0007] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0008] The present invention provides a method for scaling down particle grading of a dammed body physical model, comprising the following steps:

[0009] Step 1: Obtain the particle size distribution test results of the natural state dam body, the result of which is a certain particle size d i (Unit: mm) and the corresponding cumulative percentage of soil mass smaller than the particle size P i (Unit: %), according to particle size d i Arrange from large to small and draw a gradation curve;

[0010] Step 2: According to the requirements of the landslide dam physical model test, determine the maximum allowable particle size d' of the soil particles required for the test. max According to the particle grading test results of the natural state landslide dam, the maximum particle size of the soil particles in the natural state landslide dam is d max , the minimum particle size is d min ;

[0011] Step 3: Set the scale ratio n = d max / d′ max , the result is an integer;

[0012] Step 4: According to the grading curve, obtain the particle size d corresponding to P = 50% 50 ;

[0013] Step 5: Assume that the particle size of the soil in the physical model of the landslide body after scaling is d i ′, the corresponding cumulative percentage content of soil mass smaller than the particle size P i ′, then when d i ≥d 50 When the scale is reduced, d i ′=d i / n,P i ′=P i ;

[0014] Step 6, for d i ≤d 50 , there are two cases:

[0015] If the minimum particle size of the natural dam body d min <n 2 0.005, then when d 50 ≥d i ≥n 2 0.005, set d 50 ≥d i ≥n 2 There are j particle sizes (including n2 0.005 particle size or the closest particle size), the particle sizes are numbered from small to large as m=2…j+1, after scaling P i ′=P i ; When n 2 0.005>d i When the scale is reduced, d i ′=d i , P i ′=P i ;

[0016] If the minimum particle size of the natural dam body d min ≥n 2 0.005, then let d 50 ≥d i ≥d min There are j particle sizes in total, and the particle sizes are numbered from small to large as m=2…j+1. P i ′=P i .

[0017] Preferably, in step 1, according to the national test method standard "Standard for Geotechnical Test Methods" (GB / T 50123-2019), the particle grading test results of the natural state dam body are obtained through indoor tests or field tests.

[0018] Preferably, for d calculated in steps 5 and 6 i ′, when d i '≥10mm, the result is rounded to an integer; when 1mm≤d i When '<10mm, the result is rounded to one decimal place; when 0.1mm≤d i When '<1mm, the result is rounded to 2 decimal places; when d i When ′<0.1mm, the result is retained to 3 decimal places, which can facilitate the subsequent better preparation of particle grading.

[0019] Compared with the existing technology, the particle grading scaling method for the physical model of a landslide dam mentioned in the present invention has the following advantages and beneficial effects:

[0020] 1) This method is applicable to the production of scaled models of natural dam structures with various particle gradations and similar criteria.

[0021] 2) This method is simple to calculate, and the particle size distribution required for the physical model of the dam body can be obtained with only one calculation.

[0022] 3) The gradation after scaling down and the original gradation after scaling down are described by a definite mathematical formula, which has a good guiding role in the study of the scaling effect of the dam body.

[0023] 3) Cumulative percentage content of soil mass P i =50% is the key parameter of various characteristics of the dam body, i The particle size corresponding to >50% is linearly scaled, P i The nonlinear scaling of the particle size corresponding to ≤50% can not only meet the requirements of the physical model test of the landslide body, but also ensure the continuity of the grading curve after scaling, which has strong operability for actual work. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a comparison diagram of the original gradation curve and the scaled gradation curve of the dam body in Project A in the embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solution of the present invention, the preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the drawings are only for illustrative purposes and cannot be understood as limiting this patent.

[0026] Attachment Figure 1 This is a comparison chart of the original gradation curve of the landslide dam body of Project A and the gradation curve after scaling. The figure shows the original gradation curve of the landslide dam body of Project A and the gradation curve after scaling.

[0027] The following will be combined with the appended Figure 1 , clearly and completely describe the technical solutions in this invention.

[0028] like Figure 1 As shown, Example 1 of the present invention provides a method for scaling down the particle gradation of a soil mass in a physical model of a landslide body, comprising the following steps:

[0029] 1) The particle size distribution data of the original soil of the dam body of Project A is shown in Table 1 below:

[0030] Table 1 Particle size distribution of the original soil of the landslide dam in Project A

[0031]

[0032] 2) According to the requirements of the landslide dam physical model test, determine the maximum allowable particle size d' of the soil particles required for the test max =40, according to the test results, the maximum particle size of the natural landslide dam soil particles is d max =400, the minimum particle size is d min =2.

[0033] 3) Scale ratio n = d max / d′ max , the result is an integer, n=10.

[0034] 4) Obtain the particle size d corresponding to P = 50% according to the grading curve 50 =130.

[0035] 5) Assume that the particle size of the soil in the physical model of the landslide body after scaling is d i ′, the corresponding cumulative percentage of soil mass smaller than the particle size is P i ′, then when d i ≥150, after scaling d i ′=d i / 10,P i ′=P i .

[0036] 6) Minimum particle size of dam body d min ≥n 2 0.005=0.5, then let 100≥d i There are j = 8 particle sizes between ≥2, and the particle sizes are numbered from small to large as m = 2 ... 9. P i ′=P i .

[0037] 7) The scaled gradation data (unreduced) of the dam body of Project A are shown in Table 2 below:

[0038] Table 2 Soil particle size distribution after scaling down of Project A (unreduced)

[0039]

[0040] 8) For the calculated d i ′, when d i '≥10mm, the result is rounded to an integer. When 1mm≤d i When '<10mm, the result is rounded to one decimal place. When 0.1mm≤d i When '<1mm, the result is rounded to 2 decimal places. i When ′<0.1mm, the result is rounded to 3 decimal places, and the scaled gradation data of the dam body of Project A after reduction are shown in Table 3 below:

[0041] Table 3 Soil particle size distribution after scaling down of Project A

[0042]

[0043] According to the description and drawings of the present invention, those skilled in the art can easily use the particle grading scaling method of a landslide physical model soil of the present invention and can produce the positive effects described in the present invention.

[0044] The above is only a preferred embodiment of the present invention, but the present invention is not limited to the above specific embodiment. Those skilled in the art may make several modifications, supplements or use similar methods instead without departing from the principles of the present invention, and these should also be considered as the scope of protection of the present invention.

Claims

1. A method for scaling down the particle gradation of a dammed body physical model, characterized in that: The steps include: Step 1: Obtain the particle size distribution test results of the natural state dam body, the result of which is a certain particle size d i And the corresponding cumulative percentage content P of soil smaller than the particle size i , according to the particle size d i Arrange from large to small and draw a gradation curve; Step 2: According to the requirements of the landslide dam physical model test, determine the maximum allowable particle size d' of the soil particles required for the test. max According to the particle grading test results of the natural state landslide dam, the maximum particle size of the soil particles in the natural state landslide dam is d max , the minimum particle size is d min ; Step 3: Set the scale ratio n = d max / d′ max , the result is an integer; Step 4: According to the grading curve, obtain the particle size d corresponding to P = 50% 50 ; Step 5: Assume that the particle size of the soil in the physical model of the landslide body after scaling is d i ′, the corresponding cumulative percentage content of soil mass smaller than the particle size P i ′, then when d i ≥d 50 When the scale is reduced, d i ′=d i / n,P i ′=P i ; Step 6, for d i ≤d 50 , there are two cases: If the minimum particle size of the natural dam body d min <n 2 0.005, then when d 50 ≥d i ≥n 2 0.005, set d 50 ≥d i ≥n 2 There are j particle sizes between 0.005 and 0.005, and the particle sizes are numbered from small to large as m=2…j+1. P i ′=P i ; When n 2 0.005>d i When the scale is reduced, d i ′=d i , P i ′=P i ; If the minimum particle size of the natural dam body d min ≥n 2 0.005, then let d 50 ≥d i ≥d min There are j particle sizes in total, and the particle sizes are numbered from small to large as m=2…j+1.

2. The method for scaling down the particle grading of a landslide dam physical model according to claim 1, characterized in that: In step 1, the particle grading test results of the natural state dam body are obtained through indoor tests or field tests in accordance with national test method standards.

3. The method for scaling down the particle grading of a landslide dam physical model according to claim 1, characterized in that: For d calculated in steps 5 and 6 i ′, when d i '≥10mm, the result is rounded to an integer; when 1mm≤d i When '<10mm, the result is rounded to one decimal place; when 0.1mm≤d i When '<1mm, the result is rounded to 2 decimal places; when d i When ′<0.1mm, the result is rounded to 3 decimal places.

Images