Study of the Mechanism of Fracture Grouting in Deeply Buried Rock Strata Based on Bingham Fluid Slurry

Xiangyang Liu,Mingjing Li,Jian Lin,Huidong Xu,Chuanxin Rong,Hua Cheng

doi:10.1155/2019/6943239

Abstract

In view of the fact that the theory of fracture grouting in deeply buried rock strata seriously lags behind engineering practices, a circular fracturing diffusion model of a single fracture was established by considering numerous influencing factors of deeply buried rock strata, such as the crustal stress characteristics, rock mechanical properties, and time-varying characteristics of the serous viscosity. By setting the stress intensity factor KI equal to the material fracture toughness KIC at the fracture tip as the criterion for fracturing, the diffusion equation for the fracture grouting was derived and verified experimentally. Theoretical analysis shows that the fracture grouting pressure P0 is linearly proportional to the depth of the strata H and the lateral pressure coefficient k. The time-varying characteristics of the serous viscosity have an important influence on the grouting pressure and the diffusion radius. Its early impact is small, while its later impact is large. The diffusion radius of the grouting is indirectly proportional to the grouting pressure and the grouting flow rate. In order to increase the diffusion radius of the grouting, the grouting pressure and the grouting flow rate should be increased simultaneously. In order, the main factors influencing the diffusion radius of the fracture grouting are the time-varying characteristics of the serous viscosity, the grouting pressure, the grouting flow rate, and the depth of the strata.

Highlights

Strata grouting is one of the indispensable technologies for preventing water disasters and strengthening soft ground in underground engineering projects [1]
Strata grouting is related to the geological environment, grouting technology, grouting materials, and the grouting process, besides the uncertainty in the distribution of the pores, fractures, bedding, and joints of the rock strata. e use of grouting in engineering projects has seriously lagged behind its need, and grouting engineering designs lack scientific theoretical guidance and are still based on engineering analogy, domestic and foreign experts and scholars have carried out a great deal of research on the theory of fracture grouting
Gustafson et al [4] established the grout migration equation for a single fracture under constant pressure grouting based on the Bingham fluid constitutive model

Summary

Introduction

Strata grouting is one of the indispensable technologies for preventing water disasters and strengthening soft ground in underground engineering projects [1]. Shu-cai et al [16,17,18,19] established the grout migration equation for a single fracture on the condition of time-varying serous viscosity based on previous studies. Erefore, based on the fracture mechanics theory and fluid mechanics, in this study, we investigate the fracture diffusion mechanism of viscoelastic grout with time-varying characteristics in deeply buried rock strata and establish a theoretical single-fracture grouting model, in which the stress intensity factor KI is equal to the material fracture toughness KIC at the fracture tip. We analyze the influences of the crustal stress, grouting pressure, grouting flow rate, and time-varying characteristics of the serous viscosity on the grout fracture diffusion, which provides a theoretical basis for grouting design and the optimization of deeply buried rock engineering

Circular Fracture Diffusion Model of a Single Fracture

Grouting Fracturing Pressure and Fracture Channel Expansion Conditions

Bingham Fluid Fracturing Diffusion Equation

30 Measured initiation pressure Theoretical initiation pressure

Conclusions