| The soil-rock composite stratum represents a prevalent and intricate geological condition that arises during subway shield tunneling projects.Excavating through a soil-rock composite stratum using a shield tunneling machine can lead to abnormal soil movement near the excavation face due to significant disparities in the physical and mechanical properties of the rock and soil masses within the stratum.This movement poses a potential threat to the safety of nearby existing buildings,structures,construction personnel,and machinery.In urban areas,where the planning and design of tunnels often involve complex environments and routes,the demand for constructing small radius curves using shield machines is expected to notably increase in the future.During the construction process of small radius curved shield tunneling,the shield machine remains in a constant correction state,intensifying the disturbance to the surrounding strata and escalating the construction risks and difficulties.Consequently,the deformation behavior of the strata becomes exceedingly intricate.Currently,there is a lack of understanding regarding the ground deformation patterns caused by small radius curve shield tunneling construction and the underlying mechanisms through which excavation parameters influence ground deformation in soil-rock composite stratums.Hence,it holds significant scientific and engineering value to unveil the deformation patterns within soil-rock composite stratums induced by small radius curve shield construction.It is imperative to propose efficient and accurate prediction methods,ascertain the appropriate selection of excavation parameters for small radius curve shield tunneling,and ensure the stability of the excavation surface and surrounding strata throughout the construction process.These measures are essential for safeguarding the safety of existing buildings and structures.This paper presented a comprehensive study on the deformation laws of soil-rock composite stratums resulting from small radius curve shield construction and the optimization of tunneling parameters.The study was conducted based on the Dalian Metro Line 5 project and employed a range of research methods,including indoor tests,theoretical analysis,machine learning,and numerical simulation.Through an in-depth investigation,the research findings are outlined as follows:(1)The paper provided a comprehensive summary of the deformation characteristics exhibited by various stratums when subjected to the influence of small radius curve shield construction.Specifically,three-dimensional numerical models were established to examine the effects of linear shield tunneling and small radius curve shield tunneling on ground deformation and karst cave deformation within soil-rock composite stratums and cavernous strata,respectively.The study investigated these effects by considering essential variables such as the soil-rock composite ratio,distribution location of existing karst cave,size of karst cave,and distance between karst cave and tunnel.(2)A novel theoretical prediction formula was proposed to estimate ground deformation resulting from small radius curve shield tunneling,taking into account the impact of both soil-rock composite stratums and karst cave.The formula incorporated several key factors: the non-uniform distribution of additional cutter plate thrust influenced by slurry capacity and crowding effect,the non-uniform distribution of friction force between the shield shell and soil affected by soil softening and slurry spreading,the influence of synchronous grouting pressure,and the over-excavation of the stratum within the curve on ground deformation.Moreover,to address the significant mechanical parameter disparities between upper and lower stratums within soil-rock composite stratums,the elastic equivalence theory was introduced.By modifying the theoretical prediction formula,a new theoretical prediction formula was developed to capture the deformation of the soil-rock composite stratum caused by small radius curve shield tunneling within a double-layer elastic system.Furthermore,considering the influence of karst cave within the soil-rock composite stratums on ground deformation,the theoretical formula was refined using the superposition principle.The modified formula was then fitted using the L-M algorithm,leading to the proposal of a theoretical prediction formula for ground deformation resulting from small radius curve shield tunneling within soil-rock composite stratums containing karst cave.(3)The present study focused on analyzing the influence of construction parameters associated with small radius curved shield tunneling on ground deformation,while also investigating their global sensitivity.Key construction parameters that have a significant impact on the deformation of soil-rock composite stratums during shield construction with small radius curves were carefully selected for examination.Through statistical analysis of the calculation results,the influence patterns of individual variations in the selected construction parameters on the evolution of ground deformation were determined.Following this,the distribution type and range of each parameter that could potentially affect the deformation of soil-rock composite stratums during shield construction with small radius curves were determined.Several evaluation indicators and output indicators were chosen for analysis.To assess the global sensitivity of each parameter,the EFAST algorithm was employed.This analysis allowed for quantifying the contribution degree of each parameter to ground deformation.(4)By collecting a large amount of data during the shield tunneling process,including the dynamic change information of surrounding environment and excavation parameters,and quantifying and processing them,a corresponding database was established.The prediction model of small radius curve shield tunneling parameters based on machine learning algorithm was established,and the PSO algorithm was used to optimize the hyperparameter of the machine learning prediction model,and the prediction effect of the tunneling parameter prediction model was evaluated.Based on the predicted and read excavation parameters,the development trend of ground deformation was calculated,and various excavation parameters were optimized using grid search method to control the ground deformation within a reasonable range.Finally,the tunneling parameter prediction model and ground deformation control model were deployed on the edge device.According to the idea of layered design,the advantages of cloud computing platform and edge computing platform were integrated to establish a tunneling parameter prediction and ground deformation control system based on cloud-edge-end collaboration.This paper has 112 figures,21 tables and 223 references. |
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