This paper discribes a one-dimensional flow model to explain the basic mechanism of coal-gas outbursts.A break-start criterion of coal,as the elementary outburst criterion,is given approximately.In this ideal model,th...This paper discribes a one-dimensional flow model to explain the basic mechanism of coal-gas outbursts.A break-start criterion of coal,as the elementary outburst criterion,is given approximately.In this ideal model,the tectonic pressure before excavation,as a load on coal body,affects the break-start and then the flow field.The flow field is decoupled with the stress field,so that the gas seepage through unbroken coal body,break-start and consequent two-phase flow,and pure gas flow can be analysed independently of the stress field. The tunnelling,an external disturbance that makes the seepage intensify relatively,is an essential factor for initiating outburst.Under steady tunnelling,seepage ought to tend to be steadily progressive.From its asymptotic solution initiation criterion is obtained.This is described by three conditions,possibility condi- tion—tectonic pressure condition,incubation condition—tunnelling or gas condition and triggering condi- tion—seepage velocity condition.展开更多
Shield tunneling and post-tunneling steady seepage are accompanied by stress and displacement variations,which could induce and influence the soil arching effect.Although there are many studies on the tunneling-induce...Shield tunneling and post-tunneling steady seepage are accompanied by stress and displacement variations,which could induce and influence the soil arching effect.Although there are many studies on the tunneling-induced soil arching effect,the research about the effect of seepage on soil arching effect is extremely lacking.In this study,a numerical model is firstly established and verified by field data.Then,a series of numerical models,whose simulation method of steady seepage is verified by adopting the conformal mapping technique,are established to study the soil arching evolution of deep-buried tunneling and post-construction steady seepage.The results indicate that seepage leads to an increase in effective vertical stress,which is consistent with the existing theory.The seepage weakens the soil arching effect resulting in the height of the arch zone reducing from 2.38D(D is the tunnel diameter)to 1.25D.The seepage leads to the further development of ground consolidation settlement,but the differential displacement in the soil mass decreases.The ground reaction curve in the steady seepage condition shows a bigger value than that after excavation.It is reasonable to control the ground loss ratio in the range of 0.5–1.0%,which can minimize overburden pressure with moderate ground deformation.展开更多
基金The project supported by the National Natural Science Foundation of China
文摘This paper discribes a one-dimensional flow model to explain the basic mechanism of coal-gas outbursts.A break-start criterion of coal,as the elementary outburst criterion,is given approximately.In this ideal model,the tectonic pressure before excavation,as a load on coal body,affects the break-start and then the flow field.The flow field is decoupled with the stress field,so that the gas seepage through unbroken coal body,break-start and consequent two-phase flow,and pure gas flow can be analysed independently of the stress field. The tunnelling,an external disturbance that makes the seepage intensify relatively,is an essential factor for initiating outburst.Under steady tunnelling,seepage ought to tend to be steadily progressive.From its asymptotic solution initiation criterion is obtained.This is described by three conditions,possibility condi- tion—tectonic pressure condition,incubation condition—tunnelling or gas condition and triggering condi- tion—seepage velocity condition.
基金supported by the National Natural Science Foundation of China(Grant Nos.52090082,51938005,52122807,and 52108318)China Hunan Provincial Science&Technology Department(Grant Nos.2021RC3043 and 2021JJ30119).
文摘Shield tunneling and post-tunneling steady seepage are accompanied by stress and displacement variations,which could induce and influence the soil arching effect.Although there are many studies on the tunneling-induced soil arching effect,the research about the effect of seepage on soil arching effect is extremely lacking.In this study,a numerical model is firstly established and verified by field data.Then,a series of numerical models,whose simulation method of steady seepage is verified by adopting the conformal mapping technique,are established to study the soil arching evolution of deep-buried tunneling and post-construction steady seepage.The results indicate that seepage leads to an increase in effective vertical stress,which is consistent with the existing theory.The seepage weakens the soil arching effect resulting in the height of the arch zone reducing from 2.38D(D is the tunnel diameter)to 1.25D.The seepage leads to the further development of ground consolidation settlement,but the differential displacement in the soil mass decreases.The ground reaction curve in the steady seepage condition shows a bigger value than that after excavation.It is reasonable to control the ground loss ratio in the range of 0.5–1.0%,which can minimize overburden pressure with moderate ground deformation.
