Influence Analysis and Stepwise Regression of Coal Mechanical Parameters on Uniaxial Compressive Strength Based on Orthogonal Testing Method

Peipeng Zhang,Long Yuan,Lishuai Jiang,Xianyang Yan,Tao Zhou,Wentao Chen,Jianpeng Wang

doi:10.3390/en13143640

Abstract

Uniaxial compressive strength (UCS) and peak strain (PS) are essential indices for studying the mechanical properties of coal and rock masses, and they are closely related to mechanical parameters such as the elastic modulus (E), Poisson’s ratio (υ), cohesion (C) and internal friction angle (Φ) of coal and rock masses. This study took the No. 2-1 coal seam of Zhaogu No. 2 Mine, in Henan Province, China, as the research object. An RMT-150B servo testing machine was used to test all mechanical parameters, including the E, υ, C and Φ of coal and rock masses. Based on the principle of orthogonal testing, Three Dimensions Fast Lagrangian Analysis of Continua (FLAC3D) was used to select E, υ, C, Φ, tensile strength (Rm) and dilation angle (Ψ) as initial participation factors. Using these six parameters and a five-level combination scheme (L25 (56)), the influence of coal mechanical parameters on UCS and PS was investigated, using the software SPSS for stepwise regression analysis, and a uniaxial pressure-resistant regression prediction equation was established. The research showed that, under uniaxial compression conditions, the main parameters controlling UCS of coal masses are C and Φ; conversely, the main parameters controlling PS are E and C. UCS and PS exhibit significant linear relationships with these main controlling parameters. Here, a stepwise regression prediction equation was established through reliability verification analysis using the main controlling parameters. This prediction method produces very small errors and a good degree of fit, thus allowing the rapid prediction of UCS. The precision of the stepwise regression model depends on the number of test samples, which can be increased in the later stages of a design project to further improve the precision of the projection model.

Highlights

Uniaxial compressive strength (UCS) and peak strain (PS) are significant indices in the study of the mechanical properties of coal and rock masses and have been used widely in the design of underground mining [1,2,3,4,5]
The influence of mechanical parameters on UCS and PS has been researched and the main parameters controlling the characteristics of coal mass strength have been determined; the rapid and accurate prediction of UCS of coal masses based on mechanical parameters has been made possible
The range index was introduced to analyze the influence of mechanical parameters on UCS, based on orthogonality and the comprehensive comparability of the orthogonal experiment, both for additional analysis and to allow comprehensive comparability of the results with the orthogonal experiment

Summary

Introduction

UCS and PS are significant indices in the study of the mechanical properties of coal and rock masses and have been used widely in the design of underground mining [1,2,3,4,5]. The mechanical parameters of coal masses exhibit considerable spatial variability owing to the effects of coal-forming geological conditions and structural geology Diversity in these mechanical parameters leads to large variation in UCS and PS, which in turn has a considerable effect on the mechanical response characteristics of coal, including rock burst strength and the degree of deformation of the Energies 2020, 13, 3640; doi:10.3390/en13143640 www.mdpi.com/journal/energies. The influence of mechanical parameters on UCS and PS has been researched and the main parameters controlling the characteristics of coal mass strength have been determined; the rapid and accurate prediction of UCS of coal masses based on mechanical parameters has been made possible Such knowledge is of critical importance for the prevention and control of rock failure. An rock mechanics multifunctional was selected the loading equipment, as shown in.

Methods

Results

Conclusion