Soft Rock Roadway Asymmetric Deformation Progressively Induced By Multiple Mining And Closed Bearing Structure Recreated

The asymmetric deformation characteristic of rock roadway groups were induced by continuous mining of several working face progressively, and eventually led to large deformation failure, north-south panel, east flank mining area, Zhuji east coal mine. the high-speed production and development of mine has been seriously restricted. Combined with the 2 years on-site follow-up survey and observational data, with the methods of theoretical analysis, numerical simulation and industrial test, this paper summarized both the asymmetric deformation characteristic and the law of temporal evolution of roadway, and comprehensively discussed the influence factors of asymmetric deformation and deformation mechanism. for early asymmetric deformation and last large deformation characteristics, this paper proposed a complete closed bearing structure reconstruct technology, and floor anchor injection technology included. The industrial test was successful, the main conclusions are shown as follows:(1) The asymmetric deformation characteristic of roadway: ① the punctate and linear asymmetric deformation with “an working slope was in extrusion seriously”, “single shoulder and base angle damaged seriously” and “asymmetric floor heave”; ② Different type of roadway rock also showed a asymmetric deformation, the hard rock of roof was whole rotation subsidence; but the soft rock of roof became very crushing, even like soil, the primary deformation of it was flow.(2) Analog display the concentration factor of horizontal stress was up to 3.6, and the maximum concentration factor of vertical stress was 1.8, in anticline area. the horizontal stress of anticline core was maximum, the horizontal stress of two wings was followed, the horizontal stress near turn end was minimum. The sedimentary rock have anisotropy mechanical properties, under the conditions of orthotropic, the tangential stress in the surface of circular roadway was respectively symmetrical distribution with the direction of rock bedding and the vertical sense of rock bedding, and have obviously inhomo geneous symmetric distribution characteristics of “Four Peaks and Four Valleys”, and the largest tangential stress exists in the perpendicular direction of stratification bedding of rock. This inhomogeneous characteristics were growing bigger as the difference of E1 and E2 increases, as well as horizontal crustal stress increases.(3) The mechanical properties asymmetric distribution of roadway surrounding rock might be caused by the tilted strata roadways with a hard and soft rock interbedded surrounding rock structure, or there were some rock structural defects in part of surrounding rock, or the joints and fracture in different part of surrounding rock develop inhomogeneously. When the roadway surrounding rock would emerge obvious differences deformation by interaction with the heterogenetical stress of surrounding rocks, the asymmetric mechanical properties of surrounding rocks, and roadway support strength, the roadway would emerge asymmetric deformation. Simulation studies also indicate the presence of roadway weak interlayer will further increase the degree of asymmetric deformation, the maximum value of roadway displacement and it’s distribution interval, the rock interface separation slip and plastic zone extension.(4) The reason of early punctate and linear asymmetric deformation: ①the non-uniform distribution high tectonic stress field and shallow part surrounding rock stress; ②the mechanical properties asymmetric distribution of tilted strata roadway surrounding rock; ③the weak structure area emerged by sedimentary rock structural defects; ④ improper support method and lack of support strength. The mining influence was induction faction, under the influence of mining, the critical area of roadway surrounding rocks damaged first, other regions lagging damage or the extent of damage was relatively low, thus caused the asymmetric deformation of roadway. The non closed support method that roadway used was the real reason for eventually leading to large deformation failure. The roadway floor with no support or weak support floor heave severe seriously, the cyclical tunnel bottom cleaning lead to the surrounding rock of roadway’s sides flow gradually to the floor, the surrounding rock of roadway’s sides and roof loosened failure, furthmore, it aggravated the asymmetric deformation of roadway, and eventually led to large deformation failure.(5) The closed support method was an important means of controlling the large deformation failure of roadway late. This paper puts forward a combined and closed support repair method whit “cushion support + grouting + bolt and cable”, included the whole technical scheme and industrial process of floor anchor and injection technology, to construct a closed bearing ring again. The mine pressure monitoring of industrial test shows that the displacement of roadway’s sides is 66 mm, the maximum magnitude of roof convergence is 20 mm, the maximum magnitude of floor deformation is 40 mm, after repair and reinforcement.