Experimental Study on Nonlinear Seepage Characteristics and Particle Size Gradation Effect of Fractured Sandstones

Xuyang Shi,Qingxiang Cai,Xiang Lu,Wei Zhou

doi:10.1155/2018/8640535

Xuyang Shi, Qingxiang Cai + Show 2 more

Open Access

https://doi.org/10.1155/2018/8640535

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Abstract

Seepage mutation of fractured rock mass is one of the main inducements of dump slide and other disasters. Pore structure is a significant factor affecting the seepage characteristics of fractured rock mass, while particle size gradation has an important effect on the distribution of pore structure. Through the self-developed experimental system, the nonlinear seepage test on the fractured sandstones of the coalseam roof was conducted to investigate the influence of seepage pressure, porosity, and fractal dimension. Besides, the nonlinear seepage model was established by Barree–Conway theory. The results showed that, during the seepage process of fractured sandstone, there were significant nonlinear characteristics, which increased with the increase of the seepage pressure. With the increasing porosity, there was greater average pore size of fractured sandstone, stronger permeability, and weaker nonlinear seepage. The seepage characteristics approximated to that of Darcy model. However, with increasing grading fractal dimension, there were smaller average pore size of fractured sandstone, weaker permeability, and stronger nonlinear seepage. The seepage characteristics approximated to that of Forchheimer model.

Highlights

During the mine exploitation, local fractured rock mass structure was formed due to geological movement or mining activity, such as waste dump, fault fracture zone [1,2,3,4], collapse pillar [5], and caving zone [6]
In addition to mining engineering, filling materials of the dam foundation and roadbed are fractured rock mass [8, 9] in the construction project, and there is a series of hidden dangers of water inrush. erefore, it is of great significance to clarify the seepage characteristics of fractured rock mass for the prevention and control of geological disasters caused by seepage
It is found that the seepage behavior of fractured rock mass has obvious nonlinear characteristics, and the traditional linear equation cannot be used to characterize the nonlinear seepage behavior of fractured sandstones [15,16,17,18,19]

Summary

Introduction

Local fractured rock mass structure was formed due to geological movement or mining activity, such as waste dump, fault fracture zone [1,2,3,4], collapse pillar [5], and caving zone [6]. It is found that the seepage behavior of fractured rock mass has obvious nonlinear characteristics, and the traditional linear equation cannot be used to characterize the nonlinear seepage behavior of fractured sandstones [15,16,17,18,19]. A large number of experimental studies showed that seepage properties of fractured sandstones are influenced by many factors. To this end, Yu et al [21] concluded that the seepage ability of different lithological samples is limestone, sandstone, mudstone, and gangue by descending order. Pore structure of the porous medium is an important influential factor of seepage characteristics, so the grading of fractured rock mass has a large effect on seepage characteristics. Influences of porosity and grading in nonlinear seepage of fractured sandstones were analyzed

Sample Preparations and Experimental Scheme

Nonlinear Seepage Model of Fractured Sandstones

Findings

Experimental Result and Analysis