Mechanical properties and reasonable proportioning of similar materials in physical model test of tunnel lining cracking

When the shearer cuts coal or rock with different hardness, it will produce corresponding cutting state information. This paper develops a simulation cutting experiment system for the drum shearer based on similarity theory. It took the spiral cutting drum of a shearer as the research target and derived the principal similarity coefficients through the dimensional analysis method. Meanwhile, this paper designed the structure of the cutting power system and hydraulic system. Then, it chose a certain amount of coal powder as an aggregate, cement 325# as cementing material, sand, and water as auxiliary materials to prepare simulated coal samples. The paper adopted the orthogonal experiment method and used a proportion of cement, sand, and water as the influencing factors in designing a simulated coal sample preparation plan. In addition, it utilized the range analysis method to research the influence of various factors on the density and compressive strength of simulated coal samples. Finally, it conducted simulated coal sample cutting tests. The results show that the density of the simulated coal samples is between 1192.59 Kg/m3–1483.51 Kg/m3, and the compressive strength range reaches 0.16 MPa–3.94 MPa. The density of the simulated coal sample is related to the mass proportion of cement and sand. When the ratio gradually increases, the influence of sand increases. Furthermore, the compressive strength is linearly proportional to the proportion of cement. The self-designed simulation cutting experiment system could effectively carry out the relevant experiments and obtain the corresponding cutting condition signals through the sensors. There are differences in vibration signals generated by cutting different strength materials. Extracting the kurtosis value as the characteristic value can distinguish various cutting modes, which can provide a reliable experimental solution for the research of coal-rock identification.

Design and Application of Simulating Cutting Experiment System for Drum Shearer

It is important to systematically investigate the similar materials with high similarity ratio and low strength in multilayer shale deposits, to provide a scientific basis and experimental basis for the research of underground mining of multilayer shale deposits. In this paper, using an orthogonal experimental method, the physical and mechanical parameters of different material proportions were analyzed with four control factors of mica powder/standard sand, filling material/bonding material, Portland cement/gypsum, silicone oil ratio. Twenty-five groups of material proportioning schemes were designed, and the density, porosity, compressive strength, and elastic modulus of each group of materials were measured. Through the range analysis and significance analysis, the influence of control factors on the material parameters was explored, and multivariate linear regression analysis of test results was carried to eliminate outliers. The result showed that the physical and mechanical parameters of similar materials prepared according to the proportioning scheme were widely distributed, which can meet the preparation requirements of similar materials with different lithologies. The density and compressive strength were most affected by the ratio of Portland cement/gypsum, the porosity was most affected by the ratio of filling material/bonding material, and the elastic modulus was mainly controlled by the silicone oil ratio. The proportioning scheme was applied to three similar prepared shale materials with large lithology differences. The error between actual similar constant and design similar constant of low strength similar material was less than 1.62%. The physical and mechanical parameters of similar materials were in good agreement with the original rock.

Experiments on Material Proportions for Similar Materials with High Similarity Ratio and Low Strength in Multilayer Shale Deposits

Experimental Study on Similar Materials for Fluid–Solid Coupling for Model Test of Water Inrush in Karst Tunnel

To optimize the construction scheme of water-rich faults in long tunnels and ensure the safety of construction, mud and water inrush test must be performed. The orthogonal design method is used to perform a proportioning test, and similar materials for the mud and water inrush test are developed. Subsequently, the relationship between material parameters and control factors are quantitatively analyzed using a numerical method. Through range analysis, the influence rule and correlation of each factor on the material parameters are obtained. Through variance and multivariate regression analysis, it is found that the main control factor is crucial for controlling the corresponding parameters. In addition, based on multivariate regression analysis, a new empirical formula (regression model) is fitted and the residual analysis of the obtained model is performed. The results show that the regression model is normal. The maximum relative error of the fitting test data was used to remove the permeability coefficient, except for 16.7554% (< 20%), the remainder were less than 3%. This indicated that the test data were reasonable and the empirical formula reliable. The empirical formula can be used to determine the ratio of similar materials in soft surrounding rocks of water-rich faults quickly.

Experiment Study on Proportioning of Similar Materials in Weak Surrounding Rocks of Rich-Water Faults

The invention discloses a model test device for simulating the permeability of a surrounding rock at a fault of a tunnel. The model test device comprises a pipe main body, a base plate located below the pipe main body, a buttress located below the base plate, a collecting pool connected to the bottom of one end of the base plate, a water pressure gauge and a water inlet pipe respectively connectedto the top of the pipe main body, a water tank connected with the water inlet pipe, a movable-fixed pulley group connected with the water tank and a measure gauge for facilitating the reading of theheight of water head of the water tank, wherein the water in the water tank enters the pipe main body from the water inlet pipe, and the water pressure is read by the water pressure gauge; a similar material is poured into an opening end of the pipe main body, a calibrated scale is arranged on the pipe main body for reading the thickness of the similar material, and the flow of the water seeping from the similar material is collected and read by the collecting pool; the height of the water tank is controlled by winding a rope on the movable-fixed pulley group, and different water pressures canbe provided for the pipe main body. By adopting the device, the permeability of the similar material of the fault under different water pressures and different outburst prevention thickness conditions can be simulated, and the test process is easy to operate, simple and effective.

Model test device for simulating permeability of surrounding rock at fault of tunnel

The invention provides a method for researching dynamic response characteristics of a fault slope under the blasting inertia force effect. The method comprises the following steps that a model box ismounted on a vibration table, then, according to the structures of a surrounding rock prototype and a fault crushed zone prototype, slope model footwall surrounding rock is poured in the model box through a surrounding rock similar material firstly, then a slope model fault is poured on the upper part of the slope model footwall surrounding rock through a fault crushed zone similar material, finally, slope model hanging wall surrounding rock is poured on the upper part of the slope model fault through a surrounding rock similar material, curing forming is conducted under the natural condition,and thus a slope test model is obtained; a plurality of monitoring instruments are embedded in the slope test model; blasting simulation vibration waves with different vibration variables are loadedto the slope test model for an orthogonal test; and the inclination and thickness of the slope model fault in the slope test model are changed, the steps are executed repeatedly, and according to themonitoring result of the monitoring instruments, the dynamic response changing rule of the fault-containing slope under the blasting vibration inertia force effect is obtained.

Du Chaofei

Papers

Experiment Study on Proportioning of Similar Materials in Weak Surrounding Rocks of Rich-Water Faults

Model test device for simulating permeability of surrounding rock at fault of tunnel

Method for researching dynamic response characteristics of fault slope under blasting inertia force effect