The Tunnel Stability Studies Of Shallow Buried Bias Weak Rock

Taking a newly built railway Ningxi Xi’an to Nanyang kiln ditch on the tunnel asengineering background, according to the author’s research results, combined with access tothe relevant information and research literature, the relevant results are summarized, first tothe engineering analogy method, lists the selection of construction scheme, and have beenpublished and reference author study of forming deep buried tunnel related design experienceand methods of concept and reference in the underground engineering construction andapplication, with reference to its conclusion and research, a detailed analysis of shallowtunnel construction technology and stress characteristics.On the basis of this, the complex softsurrounding rock section start advance geological forecast work, proven geological condition.The construction site of a kiln ditch tunnel advanced geological forecast, proved that theperiod of formation lithology, rock properties and the distribution of buried depth, binding:new railway Ningxi Xi’an to Nanyang section tunnel special geological survey report ongeological prediction results are given for engineering treatment recommendations andmeasures, so as to the security and stability of tunnel construction, design provides thehydrological geology and engineering geology basis, and for the introduction of numericalsimulation and site monitoring measurement as the research means for making bedding.For better study diluvium soil mechanical properties of Q₄^al1, through field sampling andindoor three axis shear test for the foundation, to earth stress-strain characteristics and MooreKulun model equation, in consideration of the soil elastoplastic mechanical performance,introduced to the undisturbed soil Q₄^al1three axial compression experiment based on thecondition that the internal friction angle of soil cohesion, said the constitutive equations, andthrough experimental results clearly the elastic constants and strength parameters, and on thebasis of the theory for the further numerical simulation analysis of rock constitutive modeland calculation parameters provide the basis.Using the finite element software as a means of numerical simulation analysis is madeinto the tunnel, topographic information related to establishment of three-dimensionalanalysis model, quantitative analysis of the reasonable method of tunnel under excavation oftunnel surrounding rock and supporting structure stability. First put forward the engineeringgeological conditions and reasonable construction method, to keep the core method and benchmethod for comparison of the numerical simulation method in determining appropriate, leftafter the core method to surrounding rock stability is the premise for the tunnel overlyingdiluvium clay and shallow buried tunnel stress characteristics of simulation to determine thereasonable step excavation height and left and right section tunneling sequence. Comparisonand selection of3.5m,4.5m,5.5m step excavation height determine reasonable excavation height. In determining the excavation height of premise about section tunneling sequencecomparison, determine a reasonable control section tunneling sequence.On this basis, in order to optimize the excavation method as the main research object, theauthor puts forward the optimal leave core method, through and not do before theoptimization of the core contrast method surrounding rock stress and displacement field thatthe optimal the core of the stability of the method after and suitability. The results show that:the optimized method for displacement control core there is great advantage, and surroundingrock stress and stability were not before optimization is obviously improved. Through thesimulation of stress field and displacement field for the construction methods clearly weakface and control the excavation step provides the theory basis for construction and groutingreinforcement to provide the reference. Later, for supporting structure is to bolt-shotcretesupport for research object, comparing the different parameters of the bolt supporting scheme.This paper puts forward reasonable bolt-shotcrete support measures and support parameters,plan, and the scheme will be used in ShiYao ditch a number of research for the safety andstability of the tunnel.Through the channel tunnel kiln in practical engineering application, the actualmonitoring data were analyzed, and made a comparison with numerical simulation. At thesame time, the bias of the shallow section area of Quaternary Holocene silty clay (Q₄^al1)railway tunnel surrounding rock, monitoring measurement technology for reference accordingto the practical tunnel engineering geological characteristic, considering the security andstability of the principle of "advanced forward after reinforcement, reasonable excavationmethod, key control arch deformation" philosophy for tunnel of and monitoring. Taking apractical construction and site monitoring measurement data and other information"feedback" to construction process, simulation of settlement data and the monitoring data arebasically the same, the research results are correct, then the reasonable guiding the designoptimization and the construction site.In the feedback data to correct model on the basis of anchor optimization scheme: cancelthe arch bolt, cost savings, reduce the cost of. On this basis, and verified through numericalsimulations, through comparative study of mechanical properties and have no anchor boltmechanical effect, the mechanical characteristics of bolt stress. On engineering analogymethod, the similar geological conditions of bolt stress rule to make the comparison,illustrates the feasibility of optimized scheme.According to the monitoring data feedback to guide tunnel construction. To theconstruction site to take two measures for strengthening: each side wall arch waiststrengthening and application of anchor and the two arch foot applied the "locking bolt"strengthening scheme. Late field monitoring results show that: This program on the deformation control achieved good results, but also shows the importance of controllingdeformation, and the implementation of timely, reasonable reinforcement.According to the research results and research results, the numerical simulation of bias ofthe shallow soft rock tunnel excavation method and key technology of initial support to makemain summary: excavation method has an important influence on the settlement, for primarysupport of tunnel timbering opportunity and support parameters to control the settlement alsohave effect. The conclusion of the kiln ditch tunnel project follow-up construction process toprovide theoretical guidance, and "feedback" is applied to a tunnel kiln ditch constructionplan. On this basis, the kiln ditch tunnel project follow-up construction problems encounteredin the process of optimization of the construction scheme for the scene of countermeasures:Problems and solutions focus on research, in ensuring the kiln ditch on the tunnel stabilityunder the premise to extract the optimization scheme. Summary on the tunnel kiln ditchengineering experience, similar to the engineering and related process and provide atheoretical basis.