A method for generating random artificial soil or artificial stone based on 3D printing

Abstract

The application discloses a method for generating random artificial soil or artificial stone based on 3D printing, which adopts the following steps: 1) determining a spatial variability model and statistical characteristics of simulated artificial soil or artificial stone, generating a random field distribution of set parameters, and obtaining corresponding parameters of each unit soil body; 2) selecting reinforcing materials, base materials and cementing materials, and obtaining a relationship curve between the mixing amount of the reinforcing materials and the parameters of the related artificial soil or artificial stone through experiments; 3) obtaining the parameters of the unit soil body and the corresponding mixing amount of the reinforcing materials, and then converting the parameters into the layer ratio of the unit soil body base material and the reinforcing material to input a 3D printing control computer; and 4) printing according to units until the printing of all units in the random field is completed, and the random artificial soil or artificial stone is generated. The application can construct a rock-soil sample generated by using the random field theory in a three-dimensional space, and is used for verifying whether the random finite element method is correct.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of geotechnical engineering, and more particularly relates to a test sample preparation method suitable for studying soil randomness. BACKGROUND

[0002] Due to long-term geological tectonic movement, geotechnical engineering often has the characteristics of parameter uncertainty in space, i.e., spatial variability. Numerous studies have shown that the spatial variability of soil often has a non-negligible impact on slope stability, foundation bearing capacity and pile deformation characteristics, which poses a great challenge to various engineering construction.

[0003] Firstly, most current design specifications tend to regard geotechnical bodies as a kind of homogeneous material, and take uniform geotechnical parameters, but in actual engineering, there are often characteristics of large local parameter variability, so the judgment of safety factor and reliability index is not accurate, which is also a major cause of engineering accidents. Secondly, for actual construction design, only the stratum variability is considered, and the geological information of stratum distribution is inferred through drilling data, and less consideration is given to the variability of soil parameters. Finally, the mathematical expression of the spatial variability of soil parameters mainly includes two kinds: random variable method and random field method. The random variable method regards the soil parameter as a specific random variable, while the random field method regards the soil profile as a random variable, which is an extension of the random variable method in the spatial dimension. The random variable method is more basic and is the most basic simulation method. However, the characteristics of soil points are not completely random, and the correlation between points generally decreases with the increase of distance between points. Therefore, while considering the randomness of soil parameters, the correlation between points should also be considered. Therefore, the random field method is currently used for description, and methods such as central point method, K-L decomposition method and covariance matrix decomposition method are used for discrete generation of random fields. At present, the research on the variability of soil parameters mostly stays in describing the variability and correlation of soil parameters using random field theory, and then calculating through finite element software to explore the method of generating random fields and the influence of various parameters, lacking real test data support.

[0004] Therefore, it has become an urgent need for the research of geotechnical variability to develop an accurate generation technology suitable for random artificial soil or artificial stone, which provides a new method for the research of parameter variability and stratum variability. SUMMARY

[0005] The application aims to solve the problem of lack of test verification in the research of spatial variability of geotechnical bodies, and provides a random artificial soil or artificial stone generation method based on the principle of 3D printing layering method. This method can construct the geotechnical sample generated by the random field theory in three-dimensional space, and is used to verify the correctness of the random finite element method.

[0006] The technical scheme adopted by the present application to solve the technical problems existing in the prior art is: a method for generating random artificial soil or artificial stone based on 3D printing, adopting the following steps:

[0007] 1) Determine the spatial variability model and statistical characteristics of the simulated artificial soil or artificial stone, generate a random field distribution of the set parameters, and obtain the corresponding parameters of each unit soil body;

[0008] 2) Select the reinforcing material according to the maximum value of the unit soil body parameters obtained in step 1), select the base material according to the minimum value, and select the corresponding cementing material according to the properties of the artificial soil or artificial stone that have been set, and obtain the relationship curve between the incorporation amount of the reinforcing material and the related artificial soil or artificial stone parameters under the quantitative condition of the cementing material through experiments;

[0009] 3) According to the unit soil body parameters obtained in step 1), and in combination with the relationship curve between the incorporation amount of the reinforcing material and the related artificial soil or artificial stone parameters obtained in step 2), the corresponding incorporation amount of the reinforcing material is obtained, and then the incorporation amount is converted into a layer ratio of the unit soil body base material and the reinforcing material and input into a 3D printing control computer;

[0010] 4) The control computer of the 3D printer receives the position information, parameter information and layer ratio of each unit in the parameter random field of the artificial soil or artificial stone, controls the corresponding valve to realize the ejection of the base material and the reinforcing material, ejects the cementing material after a set height, repeatedly controls the movement and output of the nozzle, and prints according to the unit until the printing of all units in the random field is completed, to generate random artificial soil or artificial stone.

[0011] In the step 1), the modeling of the artificial soil or artificial stone parameter random field is realized based on the method of autocorrelation function and covariance matrix decomposition through MATLAB program, and the random field distribution of the set parameters is generated.

[0012] The present application has the following advantages and positive effects:

[0013] I) The present application proposes a new method for generating artificial soil or artificial stone based on the principle of 3D printing and layering method, which provides a new idea for the generation of random samples, and compared with the original rock-soil sample preparation technology, the spatial parameters of the artificial soil or artificial stone can be controlled by using mechanical equipment for layered printing, thereby improving the fineness of the soil sample.

[0014] II) The present application provides a test method for the spatial variability of rock-soil body, broadens the research channel, provides a more reliable demonstration approach for the previous research, and makes the research of rock-soil body random field theory not only limited to theoretical derivation and numerical method, but also can be verified by experiments to verify the law of soil spatial variability.

[0015] Three) compared with the soil sample preparation method such as shakeout method, the density of soil body can be more accurately controlled, and through computer control, different shapes of soil samples with corresponding density and strength can be generated by providing the same material, which is more convenient and intelligent.

[0016] In summary, the present application solves the limitation that the current research on soil body parameter randomness is only based on numerical software simulation, provides a new method for soil body randomness research, and can verify the correctness of numerical modeling by verifying the calculation results of random soil body modeling with the experimental results of random artificial soil or artificial stone printing, thereby forming a closed loop of proof. BRIEF DESCRIPTION OF DRAWINGS

[0017] Fig. 1 is a random field parameter schematic diagram generated by the covariance matrix method of step 1) of the present application;

[0018] Fig. 2 is a relationship curve between the incorporation amount of the reinforcing material and the related artificial soil parameter (friction angle) obtained in step 2) of the present application;

[0019] Fig. 3 is a unit soil material distribution schematic diagram obtained in step 4) of the present application.

[0020] In the figure: 1, base material; 2, cementing material; 3, reinforcing material. DETAILED DESCRIPTION

[0021] In order to further understand the invention content, characteristics and effects of the present application, the following examples are given, and the detailed description is as follows in combination with the drawings:

[0022] A method for generating random artificial soil or artificial stone based on 3D printing adopts the following steps:

[0023] 1) Determine the spatial variability model and statistical characteristics of the simulated artificial soil or artificial stone, generate the random field distribution of the set parameters, and obtain the corresponding parameters of each unit soil body;

[0024] 2) Select the reinforcing material according to the maximum value of the unit soil body parameters obtained in step 1), select the base material according to the minimum value, and select the corresponding cementing material according to the properties of the artificial soil or artificial stone that has been set, and obtain the relationship curve between the incorporation amount of the reinforcing material and the related artificial soil or artificial stone parameters under the condition of the cementing material quantity through experiments;

[0025] 3) According to the unit soil body parameters obtained in step 1), and in combination with the relationship curve between the incorporation amount of the reinforcing material and the related artificial soil or artificial stone parameters obtained in step 2), the corresponding incorporation amount of the reinforcing material is obtained, and then the incorporation amount is converted into the layer ratio of the unit soil body base material and the reinforcing material and input into the 3D printing control computer.

[0026] 4) The control computer of the 3D printer receives the position information, parameter information and layer ratio of each unit in the parameter random field of the artificial soil or artificial stone, controls the corresponding valves to realize the spraying of the matrix material and reinforcing material, sprays the cementing material after the set height is reached, and repeatedly controls the movement and output of the nozzle to print unit by unit until all units in the random field are printed to generate random artificial soil or artificial stone.

[0027] It should be noted that the cementing material is added to ensure that the soil unit does not collapse during printing. After spraying out a set number of layers of material, the cementing material is used to reinforce and shape the soil. The amount of cementing material added can be zero if the soil unit can remain upright during printing.

[0028] In this embodiment, step 1) involves using a MATLAB program to model the random field of parameters for artificial soil or artificial stone based on autocorrelation function and covariance matrix decomposition, generating a random field distribution with set parameters. However, the method for generating the random field distribution with set parameters is not limited to the above method; KL series expansion, covariance matrix method, LS method, etc., can also be used to generate the model.

[0029] For research examples, please refer to [link / reference]. Figs. 1-3 :

[0030] 1) Taking the generation of artificial soil under a two-dimensional random field as an example, the soil friction angle is regarded as a parameter variable of the random field, such as... Fig. 1 As shown, a 1m*1m two-dimensional random soil mass with a mean of 33° and a standard deviation of 0.125 is generated using the covariance and matrix factorization method. The element length is 5cm, the height is 1cm, the unit printing height is 1mm, and the soil mass is divided into 10 layers. Since the geological variations in the vertical direction are greater than those in the horizontal direction, the autocorrelation distances in the vertical and horizontal directions are set to 20cm and 50cm, respectively. Considering rotational anisotropy, the rotation angle is set to 22.5°.

[0031] 2) such as Fig. 2 As shown, the parameters of this random field range from 32.6960° to 33.4758°. Therefore, the friction angle of the matrix material is selected as 28°, and the friction angle of the admixture is selected as 40°. When bentonite is used in a 1 part, the relationship curve between the admixture content and the friction angle of the artificial soil is obtained from the experiment as shown in the figure. Fig. 2 As shown. Calculate the soil volume for each unit, according to... Fig. 2 Calculation of the relationship between curves Fig. 1 The admixture ratio corresponding to the soil parameters of the corresponding soil unit friction angle is used to calculate the layer distribution of the two materials in each soil unit.

[0032] 3) Through computer control of the movement of the conveying pipe and the nozzle, the nozzle is opened at the corresponding position, and the x-axis and y-axis guide rails are uniformly moved and the material is printed according to the unit position, from line to plane, printing forming, after the layer is printed, the nozzle is moved as a whole by the z-axis motor to print the next layer, and finally a complete random soil sample is formed. As shown in Fig. 3 The unit soil body is composed of three materials, namely the base material 1, the cementing material 2 and the reinforcing material 3, wherein the base material and the cementing material are printed alternately according to the layer number ratio, and the cementing material is printed for cementing after being printed to the set height.

[0033] Although the preferred embodiments of the present application are described above in combination with the drawings, the present application is not limited to the specific embodiments described above, and the specific embodiments described above are only illustrative and not restrictive. Those skilled in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection scope of the present application.

Claims

1. A method for generating random artificial soil or artificial stone based on 3D printing, characterized in that, The following steps are adopted: 1) Determine the spatial variability model and statistical characteristics of the artificial stone or artificial soil, generate a random field distribution of the set parameters, and obtain the corresponding parameters of each unit soil body; 2) Select the reinforcing material according to the maximum value of the unit soil body parameters obtained in step 1), select the matrix material according to the minimum value, and select the corresponding cementing material according to the properties of the artificial stone or artificial soil that have been set, and obtain the relationship curve between the reinforcing material incorporation amount and the related artificial stone or artificial soil parameters under the quantitative condition of the cementing material by doing experiments; 3) According to the unit soil body parameters obtained in step 1), combined with the relationship curve between the incorporation amount of the reinforcing material and the related artificial stone or artificial soil parameters obtained in step 2), the corresponding incorporation amount of the reinforcing material is obtained, and then the incorporation amount is converted into the layer ratio of the unit soil body matrix material and the reinforcing material and input into the 3D printing control computer; 4) The control computer of the 3D printer receives the position information, parameter information and layer ratio of each unit in the parameter random field of the artificial stone or artificial soil, controls the corresponding valve to realize the ejection of the matrix material and the reinforcing material, ejects the cementing material after ejecting to a set height, repeatedly controls the movement and output of the nozzle, and prints according to the unit until the printing of all units in the random field is completed, to generate the random artificial stone or artificial soil.

2. The method for generating random artificial soil or artificial stone based on 3D printing according to claim 1, characterized in that, In the step 1), the modeling of the artificial stone and artificial soil parameter random field is realized by the MATLAB program based on the autocorrelation function and the covariance matrix decomposition method, and the random field distribution of the set parameters is generated.

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