Inversion Analysis Of Stability Of Hydraulic Tunnels During Construction And Operation Period

Improving the comprehensive utilization of water resources,optimizing the development and layout of regional water conservancy,and steadily promoting the development of large hydropower are the reform and development priorities of water resources and hydropower in the 13th Five-Year Plan.The hydraulic tunnel carries important functions such as water diversion,water supply and drainage,and plays an important role in realizing the reform and development goals.However,many hydraulic tunnels are often faced with problems such as complicated environment,complicated rock mass response and complicated force situation of structures during the construction and operation period,which brings great challenges to the safe construction and stable operation of the tunnel.Therefore,how to truly reflect the complicated impact of the environment,how to reasonably simulate the complicated rock mass response,and how to fully consider the complicated force situation of structures,and then establish a more complete system for inversion analysis of stability of hydraulic tunnels during the construction and operiation period,has important practical significance and economic value for enhancing the construction efficiency and ensuring the stability of operation.In view of the above,several key issues about inversion analysis of stability of hydraulic tunnels during the construction and operiation period are investigated,including inversion analysis method for the in-situ stress field,quantificational analysis model of excavation disturbed zone,dynamic inversion analysis method for stability of sourrounding rocks during the construction period,inversion analysis of seepage and stability analysis during the operation period.Analysis models and calculation methods are proposed and their reliability and applicability is calibrated to be favorable by numerical experiments and engineering application.The main contents of this dissertation are described as follows:(1)Considering the influence of formation erosion,rock mechanics and fault structure on the in-situ stress field in complicated geological conditions,an in-situ stress inversion method is proposed,based on the stratigraphic erosion simulation and lateral pressure coefficient method.Based on the erosion principle and elastoplastic finite element,the effect of stratigraphic erosion process on in-situ stress field is simulated by excavating stratum layer by layer.Based on the equivalent principle of strain energy,the equivalent mechanical parameters of the implied fault element are obtained,and the failure criterion of the element is established.The complicated fault structure is implied in the rock elements by using the implied fault elements,which reduces the difficulty of modeling.Through the establishment of the lateral pressure coefficient model,the geostress field distribution in ancient times is obtained.Combined with the unloading effect simulation method and the implicit fault simulation method,the evolution process of the stress field from the ancient to the present is simulated,and ensures the distribution rules of in-situ stress field can be reflected.Based on the inverse distance weighted interpolation method,the correction method of the in-situ stress field is investigated,which ensures the coincidence of the stress value at the measuring point.Finally,it is proved by the engineering example.The results shows that the inversion analysis method proposed in this paper can obtain a reasonable in-situ stress field and provide reasonable initial stress conditions for the dynamic inversion of the tunnel stability during the construction period.(2)Considering the spatial effect of the deterioration of rock mass parameters in the excavation disturbed zonearound the tunnel,the displacement-radius quantitative analysis model of the rock mass parameters is established.The evolution of the excavation disturbed zone of the surrounding rocks is analyzed from the macroscopic and microscopic aspects.It is suggested that the main characteristics of the rock mass degradation can be described according to the degree of deterioration of the rock mass,the deterioration law of the rock mass parameters along the depth and the deterioration range of the disturbed rock mass.Based on the existing quantitative analysis models,a displacement-radius correlation quantitative analysis model is established,which can reflect the deterioration characteristics of the excavation disturbed zone.The effects of the parameters in the model and the effects of displacement and radius on the model are analyzed.The meanings and ranges of the parameters to be determined are clarified.Finally,the engineering applicability of the model is verified,which lays a foundation for the further study of the parameter field inversion of the excavation disturbed zone of the surrounding rock during the dynamic construction inversion process.(3)On the basis of studying the dynamic inversion analysis method of surrounding rock stability during the construction period,the dynamic excavation simulation method of tunnel based on the deterioration model of the excavation zone and the time-dependent deformation effects of surrounding rock is put forward.The displacement-space-time correlation analysis model of the parameter deterioration is established.The dynamic identification of parameters of the excavation zone based on the displacement-space-time correlation model is carried out.The time-dependent deformation mechanism of surrounding rock and the time-dependent effect of surrounding rock deformation during dynamic excavation are analyzed,and the time-release method of excavation load is explored.Based on the displacement-space-time correlation model and the time-release method of excavation load,the dynamic simulation method of the dynamic excavation process of the tunnel is put forward,and a dynamic inversion analysis system of the stability of the surrounding rock is established.Finally,the practical simulation of tunnel dynamic excavation simulation method and dynamic inversion analysis method of surrounding rock stability during construction is verified by engineering examples.The proposed methods provide reliable guidance for the stability analysis of excavation during the construction period,and the initial stress condition for the stability analysis.(4)The seepage inversion and stability analysis method of the pressure tunnel during the operation period is studied.The design method for determining the thickness of the consolidation grouting for the weak surrounding rock based on the joint bearing mechanism is put forward.The method of inversion analysis of rock mass permeability is studied.The joint bearing mechanism of lining and consolidation layer is analysized,and the simulation method of joint bearing with lining and consolidation is discussed.The stability analysis method of lining structure under the action of interal water during the operation period is investigated.The coupling mechanism of concrete lining cracking and seepage is analyzed,and the corresponding seepage-damage coupling model is established.The coupling calculation method for damage and seepage in the cracking concrete lining is studied.The influence of internal water exosmosis on the seepage field caused by concrete lining cracking is investigated.And the stability analysis method for the lining sructure under external water pressure is investigated.Finally,in the case of a steel-lined pressure diversion tunnel,a numerical simulation is implemented to analyse the effect of the thickness of the consolidation layer and the distribution of the seepage field under the influence of internal water exosmosis.The results show that the proposed methods provide useful reference for the quantitative analysis of the seepage field distribution under complex conditions,the design of the anti-seepage measures and the stability analysis of the lining structure under the action of internal and external water pressure.