Rheological Failure Characteristics And Control Research Of Deep Well High Stress Soft Rock Chamber

As a typical deep mining area,mining depth of Pingdingshan mining area has reached more than 800 m,the"three-high"occurrence environment of deep coal and rock cause serious adverse effects to the mine roadway support.This paper main researches failure characteristics and surrounding rock control of deep high stress soft rock winch chamber in Pingdingshan coal mine.The field investigation,laboratory test,theoretical analysis,numerical simulation and industrial test are integrated use to study damage characteristics,stress evolution characteristics and load-bearing characteristics of deep soft rock chamber,and the chamber has been repair effectively,the main research results are as follows:?1?Has mastered the stress characteristics,the structure characteristics,the physical parameters and the creep deformation characteristics of the chamber surrounding rock.The chamber is mainly affected by horizontal in-situ stress,the average value of horizontal in-situ stress is about 24 MPa,the lateral pressure coefficient is 1.22,the development depth of surrounding rock loose circle is about 3.5 m.The mechanical properties of coal and rock mass are poor,and the surrounding rock is highly broken.The degree of surrounding rock fragmentation is relatively high.The creep deformation characteristics of surrounding rock samples under different confining pressures of 5 MPa,10 MPa and 15MPa are clarified.With the increase of axial stress level,the steady-state creep of surrounding rock are relatively short,and it is easy to enter the stage of accelerated creep failure.With the increase of confining pressure,the failure time and failure strength of rock sample increases.?2?The rheological constitutive model of rock is improved,the research results show that there are several key factors influencing the failure characteristics of surrounding rock,respectively are?₁-?₃,E₀,?₂and?₃.The numerical operation model of the chamber is constructed,the deformation and stress evolution characteristics of the surrounding rock are defined.The chamber presented a state of continuous large deformation in the whole section,there is a high degree of stress concentration at the top and bottom angles and at the joints of two sections of the chamber,as time goes on,the stress concentration coefficient keeps increasing.The deformation and failure characteristics of chamber foundation were analyzed,the failure reason is the unbalanced stress caused by tension at both ends and compression in the middle of the foundation.The maximum failure depth of the chamber surrounding rock and floor is about 12 m.?3?The main factors affecting the stability of surrounding rock in the chamber were identified.The mechanical model of the roadway's internal and external bearing structure was established,and the bearing mechanism of surrounding rock was analyzed,the effects of different supporting technologies?roof support,floor unloading,anchor cable support and grouting reinforcement?on the bearing structure and rheological deformation of surrounding rock were studied.The surrounding rock control strategy of"let,resist,place and inject"is put forward to optimize the bearing structure inside and outside the chamber.The control scheme of surrounding rock is determined as"bolt,metal mesh,shotcrete,high-strength prestressed anchor cable,full-section grouting and floor unloading".?4?Numerical simulation and industrial tests we carried out to verify the effect of the proposed control scheme for the surrounding rock of the chamber and verify the rationality of the supporting method and supporting parameters.The deformation monitoring of surrounding rock shows that after the repair of the chamber,the rheological deformation of the chamber is effectively controlled,and the overall deformation of the surrounding rock is within 10 mm,ensuring the stability of the winch chamber.The research results can provide reference for the support and surrounding rock control of deep soft rock chamber.There are 73 pictures,17 tables and 124 references in this paper.