Lancang Pb-zn Soft Tuff Rock Tunnel Failure Mechanism Analysis And Supporting Parameter Optimization Study

The support in soft rock excavation is one of great problems that affects secure production of mine. Over the years, Lancang Lead-Zinc has been encountered in the production process tuff tunnel problems. This tuff belongs to soft rock, with easy expansion, easy to collapse wet with water-oriented properties, which resulted in very unstable tunnel, there are often cave, inside the two side squeeze, at the end of drums, and even the whole cross-section deformation and failure. At present, the mining of such soft rock tunnnel to be the main means of supporting wooden car bracing, although this construction technique is simple to supporting means, but can not completely solve the problem of tunnel deformation instability, leading to rework mine often roadway and maintenance, affecting the normal production of the mine, has also increased the exploitation of intangible costs and cause significant economic losses.In this paper, Lancang Lead-Zinc soft rock roadway damage to the specific situation in order to 1700 mid-level roadway segment to study the extension objects are related to research:1,Tuff indoor studied. Carried out by the density of the tuff by the determination of moisture content experiments, micro-structure analysis, absorption experiments, the collapse of the wet-based experiments, swelling experiments, the creep characteristics, as well as point load test the conclusion that:Tuff contains such a large number of kaolinite and montmorillonite clay minerals, and easy-absorbent, this tuff low intensity, belonging to the expansive soft rock, and there is no water in dry conditions, the role of rare phenomenon of expansion and collapse of the wet; Once the tuff is in the humid environment with water, its ability to significantly reduce the resistance to collapse, swelling to increase substantially accelerated expansion, combined with climate, the temperature of wet and dry cycle, the impact of hot and cold cycles, further accelerating the soft tuff rock tunnel's deformation and failure. We can see from the experiment, the expansion of micro-tuff contained substances of roadway damage caused by the major internal factors, water and moist air is roadway damage caused by the main external factors.2,Light of the new Austrian law theory on the Lancang Lead-Zinc soft rock roadway made bolt-spray net support means to conduct a field trial lasted more than two months, and real-time monitoring, analyzing various factors affecting the experiment, the overall draw a more satisfactory results.3,Using ansys finite element simulation software, the main support parameters to optimize, including cross-section form, anchor layout parameters, the results obtained:heart arched three-section form, can effectively improve the stability of the initial period after rock excavation; with a length of 1.8m, with a radius of 2cm, elastic modulus 200GPa solid super bolt, inter-row distance of 0.75m×0.75m reduce the layout of the form of more post-rock deformation and improve the overall stability of bracing.