Study On Construction Mechanical Behavior Of Tunnel Under Non-uniform Stratum Condition

Based on the XiangShan tunnel engineering in LongXia Railway,The paperstudies the construction mechanical problem during the excavating process of theengineering in the non-uniform stratum.The section of Ⅲ、Ⅴ surrounding rockscoexisting and weak Ⅵ surrounding rocks has been studied numerically by thenonlinear finite element method calculation and practical monitoring data,presentingthe rule of the construction mechanical.Therefore, it has strong guiding significance for on-site construction to studyconstruction mechanical behavior following by it possible failure modes of primarysupport under non-uniform case surrounding rocks with bringing forwardconstruction assistant measures and the reasonable construction method,combinedwith the method optimization under the reasonable construction method of soft-weak.Some qualitative and quantitative research can be obtained.(1)For the section of Ⅲ、Ⅴ surrounding rocks coexisting, primary supportendures biggish pressure of surrounding rock, bending moment and shear owing tophysics nature of mechanics inconsistency on boundary neibourhood. The adverseeffect of the primary support is more obvious where the boundary occurs to key point.The rule of primary support under the influence of Ⅲ、Ⅴ surrounding rockscoexisting is deeply studied under Ⅲ、Ⅴ surrounding rocks coexisting which israndomly distributed in different proportions and angle on tunnel outline.(2)Construction assistant measures under the non-uniform stratum which consistsof Ⅲ、Ⅴ surrounding rocks coexisting is studyed in the paper. Researches show thatthe reinforcement effect of primary support can be better by adopting groutingreinforcement, temporary supports and exerting radial anchor around the boundaryafter the detecting of orientation and angle of Ⅲ、Ⅴ surrounding rocks coexisting.(3)In view of the conclusion we draw general comparing on Three-stepTemporary invert and Cross Diaphragm(CRD) method which contained the stresscharacteristic、the strain characteristic、the displacement characteristic of surroundingrock and the stress characteristic of support structure， the reasonableconstruction method is obtained of tunnel depth on some extent.， under theconditions of weak Ⅵ surrounding rocks region. It is deeply studyed that how the mechanics of primary support responses considering the time-space effect，differentstep length and different excavation progress. On this basis, The optimal scheme ofconstruction can be put forward for the dense-constructed area terms of primarysupport stability.(4) Through the analysis of a large number of monitoring data on surroundingrocks and support structure of Cross Diaphragm(CRD) method to qualitativly checktheoretical numerical simulation validity, the dissertation further expounded on thetrend of changes in mechanical behavior and distribution law of the rock and supportstructure at the construction phase.