Study On Engineering Geological Properties Of Aubergine Mudstone Of Taiyueshan Tunnel

The aubergine mudstone of Taiyueshan tunnel is main rock mass in this tunnel, which is closely linked to tunnel engineering. The mudstone has special engineering geological properties result in many problems in investigation and construction of this tunnel. Therefore, the study of engineering geological properties of the aubergine mudstone has great significance.In this paper, the basic profile of Taiyueshan tunnel are briefly introduced, some basic rules and mechanics parameters obtained through the indoor disintegration test and triaxial compression test. The article analyzes tunnel displacement and stress before and after excavation according to numerical simulation software.According to a series of disintegration tests, the impact on the test results considering disintegration time, sample volume size and dry-wet cycle times. The results are as follows:(1) The disintegrating amount is gradually improved with the increase of disintegration time. The weathering degree still has strong influence in disintegration process.(2) The complete block volume size has some effect on disintegration, further disintegration rate decreases with the increase of sample volume.(3) The dry-wet cycle has significant effect on disintegration process, disintegration amount raise up with the increase of dry-wet cycle times.This article presents the results of triaxial compression strength and acoustic properties of aubergine mudstone in Taiyueshan tunnel at different confining pressures by using RMT-301 rock mechanics test system and GCTS ULT-100 ultrasonic measuring system. The results show that:(1) The peak and residual strength are gradually improved with the increase of confining pressure. Although some of the stress-strain curve has abnormal effect due to uneven fracture inside rock samples, the results of peak and residual strength are proportional to the applied confining pressure.(2) The failure mode under 2, 4 and 6 MPa confining pressure following the Mohr-Coulomb failure criterion, the fracture angle after the destruction is close to the calculated angle by Mohr-Coulomb failure criterion.(3) The variation of P wave velocity is basically the same as the variation of stress-strain curve at corresponding confining pressure during the experiment process.The excavation of the tunnel are simulated by using numerical simulation software, according to compare the stress and displacement before and after tunnel excavation, the results are as follows:(1) A large displacement appears at the top and bottom of the tunnel after the excavation under no support measures situation.(2) The stress state at the bottom and sides of the tunnel changes significantly, the compressive stress turns into tensile stress. If the tensile stress exceeds the tensile strength of the rock mass, tunnel surrounding rock will be destroyed and collapsed.