Mechanism And Technology Of Yielding Shell Reticulated Shell Coupling Support In Soft Rock Roadway

The problem about support of soft rock roadway has not been solved completelyyet. It is difficult to support especially in mudding soft rock roadway with high stress,we often rework several times in order to control the long term stability of roadwaywhich affects production safety seriously and wastes high cost of roadwaymaintenance, thus to control the stability of soft rock roadway has been a significanttechnical problem which needs to be resolved immediately. In this paper, we choose850m east belt main roadway of Qujiang coal mine (mudding soft rock roadway withhigh stress) as the engineering background and apply comprehensively numericalsimulation, theoretical analysis, laboratory experiment, field monitoring, industrialexperiment and other methods around the problem about controlling the stability ofmudding soft rock roadway with high stress. We make a systematical study ofyielding shell reticulated shell coupling support mechanism and technology in softrock roadway and obtain following innovation achievements:(1) We make a triaxial creep test of argillaceous siltstone, establish a viscoelasticplasticity creep model of the whole creep process of argillaceous siltstone and deducethe three dimensional constitutive equation about this creep model; we utilize Flac3Dto analyze and obtain the creep law and plastic zone distribution law in soft rockroadway with high stress.(2) We put forward the concept of yielding shell and the construction condition,support action characteristics and support connotation of yielding shell are given. Wededuce the formula for the thickness of yielding shell, analyze the support strength ofyielding shell in soft rock roadway and determine the support strength and thicknessof yielding shell in east belt main roadway.(3) We establish the mechanical model of full size grouted prestressed boltsupport, study systematically the support mechanism of bolts which are short, thin andarranged densely, deduce the formula for the axial stress and shear stress of bolt; wededuce the formula for the surrounding rock stress along the axial direction, theradial direction and the ring direction of bolt, analyze and obtain the relationshipbetween pre tightening force of bolt, length of bolt, diameter of bolt and axial stressof bolt, the shear stress of bolt; we analyze and obtain the influence law ofsurrounding rock stress by bolt length and bolt pre tightening force; we use Flacanalyze and obtain the influence law of the deformation of soft rock roadway surrounding rock by bolt length and support density.(4) We put forward the yielding shell reticulated shell coupling supporttechnology, analyze the yielding shell reticulated shell coupling support principle, putforward the secondary support principle that we should restrict, yield and resist stress.Meanwhile, moderate restriction and yielding are needed, yielding should coordinatewith resistance. The yielding shell reticulated shell coupling support technology andmethod are given. We deduce the formula for the reservation yielding space in softrock roadway and determine the reservation yielding space in the east belt mainroadway is38cm.(5) We divide the mudding soft rock roadway surrounding rock with high stressinto yielding shell (which is in fractured zone), fractured zone, plastic zone and elasticzone. We base on viscoelastic plastic theory, consider the creep and dilatancy ofsurrounding rock, deduce the formulae for the radius of plastic zone, the radius offractured zone and the radius of yielding shell and the expression of each division. Weanalyze the deformation of yielding shell and the energy release during deformationprocess, determine the yielding shell reticulated shell coupling support strength andtime in the east belt main roadway.(6) According to the yielding shell reticulated shell coupling support theory andtechnology in soft rock roadway, we determine the control method and parameters ofsurrounding rock in the850m east belt main roadway of Qujiang coal mine and makesome industrial tests. The field application shows that using the constructiontechnology, which consists of rationalizing the shape and size of section, yielding roofcontrol construction technology and process, yielding shell, reserving yielding space,anchor reinforcement and reticulated shell lining stent, and support method cancontrol the harmful deformation of surrounding rock in the850east belt mainroadway, ensure the long term security and stability of the east belt main roadway.