Classification And Stability Study On Surrounding Rock Of Hipparion Red Clay In Shi-lou Tunnel

Depend on the major scientific research project of the Ministry of Railways, Research on Tunnel Comprehensive Technology of the Hipparion Red Clay in Lvliang Mountains Regions, on the basis of summarizing the predecessors’ research achievements, through the field sampling, indoor and field test, the theoretical analysis and calculation, field monitoring and numerical simulation and other research techniques, the surrounding rock classification and stability about the hipparion red clay of Shilou tunnel will be discussed in this paper. The main achievements are as follows:First of all, on the basis of the analysis of regional and environmental geology conditions, advanced geotechnical testing means (scanning electron microscopy, grain size analysis, energy spectrum analysis, the static triaxial test, creep test, indoor and outdoor large shear test, etc.), from the several aspects of the hipparion red clay, material composition, microstructure and physical properties, the static mechanics and deformation properties, water properties and other aspects, the engineering properties of the hipparion red clay will be analysed deeply and systematically. Results show that the structural strength of the hipparion red clay is high, the cohesive force is very big; The main factors which influence the hipparion clay strength including tuberculosis, crack and water; The creep property of the hipparion red clay will be performanced at high stress level, which can be neglected only under the low stress level.Secondly, based on the theory of extenics and the method of the entropy weight, the selection of five evaluation factors, including severe, cohesive force, internal friction angle, deformation modulus, the groundwater state, the extension evaluation model about the surrounding rock quality classification of Shilou tunnel will be set up and the determination results wil be compared with the surrounding rock. Results show that the extension evaluation results about the surrounding rock quality classification,13of18tunnel face, and the results referred in the the engineering geological prospecting report is consistent, with the accuracy rate is72.2%, which is better. Again, the influence factors about the surrounding rock stability of Shilou tunnel will be analysed, the failure mechanism of the surrounding rock will be discussed, and the deformation characteristics of surrounding rock based on the field monitoring results will be analyzed. Results show that the influence factors of the surrounding rock stability mainly include the surrounding rock pressure, the mechanical properties of surrounding rock, rock mass structure state, groundwater, construction design and time etc;The failure mechanism of the surrounding rock mainly express for plastic flow, bending the drum and the plastic wedge extrusion; The surrounding rock of hipparion red clay of the arch sedimentation is greater than the horizontal convergence, and the surrounding rock stress is high overall, a trend of " big-end-up", the surrounding rock stress tend to stable basically after60days, the surrounding rock of the moisture content and pore water pressure continues to increase, as the moisture content of surrounding rock gradually become saturated, pore water pressure tends to be stable gradually.Finally, the underground engineering general finite element software Midas/GTS will be used to build the finite element analysis model of2D and3D tunnel, respectively considering the seepage and stress coupling effect and without considering it, the complex mechanical behavior (seepage field, stress field, bolt axial force and bending moment) between surrounding rock and supporting structure in the process of hipparion red soil tunnel construction and the law of deformation (displacement field and plastic zone), which will be analyzed in comparison. Results show that considering the conditions of the water-stress coupling effect, effective stress, anchor axial force, bending moment, vault subsidence, horizontal convergence and distribution of plastic zone of hipparion red soil surrounding rock is greater than not considering it, which illustrates that groundwater seepage is the dominant factor to induce hipparion clay rock stability, so the arch and arch foot support should be strengthened in the process of construction, and discharge tunnel bottom water in time.