| With the extension of human's production and life, modern deep karst, recognized as a special karst form, has gradually attracted people's attention. As it might do harm to the cross-mountain tunnel, a series of geological engineering problems it brings about are the key points of the project. Take the Yuanliangshan deep-buried and extra long cross-mountain tunnel as an example, the outburst of water and soil under high pressure have controlled the difficulty of construction, simultaneously, becomes a very challenging theoretical problem. Based on the study of the controlled factors and mechanism of modern deep karst development, this paper has done further research on both hydrodynamic-hydrochemistry and control action to cross-mountain tunnel. Through the research, an evaluation system of its control action has preliminary been obtained, which not only enriches the engineering geology theoretical system of modern deep karst, but also shows practical significance to deep-buried cross-mountain tunnel. The main results are as follows:(1)By binary classification methods, an engineering geology classification system has been established. Geological structure patterns are used as primary indexes to divide modern deep karst into extra-thick, single tectonic, as well as composite tectonics. And the primary classification can be refined to within layers, valley, opened syncline, closed syncline and fault zone, while using position where karst develop, structure types and open state as binary indexes. Further researches have been done on the characteristics of these types.(2)Controlled factors of karst development have been studied from three aspects, including lithology, channel condition and field effect. Control action will not change with depth for soluble rock, as a material base, will not change its chemical composition with depth either. Properties and scale of channel determine the control action of channel condition. Control action of field effect has relation to channel condition. And only special channel condition exists, can field effect be brought to play.(3)Incorporate with geomechanics model and groundwater hydrodynamic model, the developmental patterns of modern deep karst can be summarized into thick-runoff, valley-excretion, syncline-runoff, fracture-discharge, and composite. Among them, syncline-runoff is refined to steep-closed, and sustained-opened, The developmental mechanism of each pattern have been further studied.(4)Take the typical modern deep karst of Yuanliangshan tunnel Maoba syncline section as an example, above all, a hydrogeological conceptual model of the tunnel region has been set up, hereafter, numerical simulation of groundwater has been performed using the software visual modflow, and a chemical simulation has been carried out based on the chemical data. In the light of simulation results, the karstification of this region can be simulated.(5)Through a series of statistical analysis on engineering examples, three aspects of modern deep karst engineering geological problems have been raised, including water-outburst and soil-outburst, instable of karst caves, tunnels and layers within caves, water under high pressure. What play key part in cross-mountain tunnel engineering are water-outburst, soil-outburst and water under high pressure. Considering it is sensible, scientific and practical to evaluate the control action which modern deep karst imposes on the tunnel, an evaluation system has been established, while using risk classification system of water-outburst and soil-outburst. Evaluation indexes are worked out through comprehensive consideration of many factors. Weight value of each index can be calculated by AHP method. Membership values of each index can be fixed by ridge shape function. Risk classification system of water-outburst and soil-outburst software is exploited using Visual Basic and Formula One(Demo). This paper takes Yuanliangshan tunnel Maoba syncline section and Wumengshan 2~# tunnel as examples to evaluate the risk of water-outburst and soil-outburst on each section. Ultimately, relevant preventive measures can be drawn up on basis of the classification and preventive principle.
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