Study On The Anchorage Mechanical Properties Of Filling Fault Fracture Rock Mass

Fault is a kind of commonly geological structure in the stratum, and there is usually a weak fracture zone near it’s fracture surface. The weak fracture zone has low overall strength and poor stability, and that causes serious threat to the safety of project construction. With the background of gubei coal fault fracture zone of huainan mining area, this paper studies the strength and the deformation characteristics of anchorage rock mass through physical model tests(different cementing materials, different aggregate gradation, different anchorage force and different anchorage ways) and numerical simulation calculation. The formation conditions of combined arch(beam) of rectangular tunnel and arch tunnel has been analysed further, and the distinguishing rules of tunnel unstability has been established. The main results are as follows:According to the complex and changeable characteristics of fault structure in mining area formation, this paper studies on anchorage mechanical properties of fracture rock mass under a variety of conditions. Results are as follows:(1) As the aggregate size or the cementing material strength increases, the mechanical parameters of fault fracture rock all present a gradually increase trend. Compared with the complete rock mass, the cracking degree of modulus of fault fracture rock is the most significant(78.82%), and the cracking degree of internal friction angle of fault fracture rock is the weakest(25.21%).(2) The peak strength and elastic modulus of fault fracture rock both present a gradually increasing trend with the increase of the anchorage force, aggregate gradation or cementating strength. In addition, when the anchorage way of fracture rock changes as no anchor to end anchor, full length anchorage, its peak strength and elastic modulus both increase gradually.(3) The primary and secondary sequence of the effect of different testing conditions on rock mass strength is that cementating strength>aggregate gradation>anchorage force>anchorage ways. The curve of anchor axial force with time mainly includes stable stage, growth stage, yield stage and the stage after peak.(4) Through numerical software, the influence law for rock strength caused by anchorage density and lateral pressure was studied. And the anchorage mechanism was analysied through the internal stress distribution characteristics of model. As close to the anchor, the anchorage stress symmetrically decreases from both ends to the middle. And it symmetrically increases from both ends to the middle as far from the anchor.(5) As the anchorage density decreases, the anchorage force increases or the pallet size increases, the thickness of anchorage combined arch presents a gradually increase trend. The influence coefficient of the control factors to the combined arch thickness can be obtained through nonlinear fitting. And we can modify the geometric relation of combined arch thickness.(6) Based on the theory of structural mechanics, the bearing capacity of combined arch(beam) of rectangular tunnel and arch tunnel has been analysied. The distinguishing rules of tunnel unstability has been established, and it has been applied to engineering case analysis.