Stability Analysis Of Rock Mass For The Sluice Junction In Hanjiang-To-Weihe River Diversion Project

In recent years, rapidly developing underground engineering has become animportant part of modern civil engineering construction. However, the correspondingengineering specifications and scientific research are still lagging behind, especiallyanalysis and evaluation on the stability of rock mass. The existing analysis andevaluation approaches are difficult to be applied to relevant engineering practiceeffectively. Therefore, an effective method for evaluating stability of rock mass ispressing required, which is capable to conduct an effective numerical analysis on theresults and provide intuitive conclusions as well.In present project, a detailed study on the stability of rock mass of caverns for theSluice junction in Hanjiang-To-Weihe River Diversion Project in Shanxi Province wascarried out. A brief review of previous research on analysis methods and instabilitycriteria for stability of surrounding rock mass is presented, followed by the introductionof the engineering situation and geological condition of the project. The selections ofthe parameters and initial field for the simulations of rock mass analysis were based onthe exploration and monitoring data. According to Drucker-Prager criterion, thequalified elastic-plastic constitutive relation of the finite element model was applied.And then commercial finite element software ABAQUS was utilized to simulate theexcavating process and supporting scheme of the case, with the evaluation of theintegral and local stability of rock mass built on the obtained stress and displacementfields. Finally three failure criteria were built to figure out the areas where yielded. Theresults indicated that,1) stress and strain concentration occured at the intersections ofthe lock chambers and traffic tunnel, water tunnel or interconnected tunnel.2)Displacements, plastic strain and pulling stress of most rock mass were reduced byapplying combined bolting and shotcrete to the model.3) With excavation furthermore,the displacements and plastic strain of rock mass increased.4) The stability of elementsnear the rock mass excavated was evidently deteriorated.5) The stress status of rockmass near Sanhekou lock chamber ranked the best, followed by Huangsanduan lockchamber and Yuelingduan lock chamber. In our model, the shear-slip destruction method was applied to simulate thecombined bolting and shotcrete, in which the supporting resistance is loaded on theexposure face of tunnel in the way of radial pressure. By analyzing the stress anddisplacement of rock mass with and without being supported respectively, the approachof supporting simulation based on shear-slip destruction was proved to be feasible.Nevertheless, this approach requires further improvement as it failed to reduce the stressand strain of rock mass effectively.Analysis of the relevant stress and strain was employed to assess various results ofevery parameter at each excavating step and evaluate the stability of each section inrock mass comprehensively. However，since the difficulty to determine the stability ofrock mass solely by quantified data, the computed results were not competent to provideany implication about it neither. This evaluation method could only figure out the areaswhere the stress, strain and displacement were significant, and where yielded, so that theengineers could pay more attentions to these areas and take corresponding protectionmeasures in engineering design and construction.