Study On Mechanical Properties And Optimization Of Structure Of Trenches Considering Spatial Effect

Engineering practice and research have shown that,depending on the width and size of the excavation,there are obvious differences in deformation and stability,and it has significant characteristics of spatial effect.However,the existing specifications only take the retaining structure on one side and the soil in the active and passive areas as the research object,and establish the safety factor algorithms,ignoring the effect of excavation width,resulting in large design waste of trenches such as underground integrated pipe galleries.To this end,the article mainly completes the following research work:(1)According to the theoretical analysis of the relationship between the anti-overturn stability with the basal heave stability and excavation width,it is found that the retaining structure on both sides of trench will limit the development and formation of the failure surface,and the stability is better.It’s very necessary to consider the effect of excavation width.(2)The "Tianhan" design software based on traditional excavation theory and the strength reduction finite element method are used to calculate the basal heave safety factor of a trench in Jingzhou.The calculation results are 2.63 and 3.58 respectively,the latter obviously higher,revealing that designing trench according to the traditional excavation theory is conservative and there is a larger space for structure optimization.(3)With the aid of ABAQUS finite element software,semi-infinite space elastic body model that doesn’t consider the size effect of excavation and infinite space elastic body model that considers the size effect of excavation are used to simulate the characteristics in mechanics and deformation of the excavation under various working conditions.According to the same result parameter under the two conditions,the limit of wide and narrow excavations is determined.By comparing the simulated values with the theoretical values obtained from the anti-overturn stabilization theory and the arc slip theory,verify excavation has a critical width,and the two classifications are scientific.(4)The basal heave failure of excavation is simulated by the strength reduction finite element method,the relationship between basal heave safety factor and excavation width is obtained,and the critical state of the excavation narrowing is determined based on it,the exact engineering definition of trench is given.(5)Based on the basal heave failure mode of trench,algorithms that can consider the effect of excavation width is derived.The method can be connected with the existing codes algorithms at the critical excavation width.On this basis,the parameter influence analysis is carried out from the two aspects of trench size and soil’s shear strength index to provide reference for similar engineering projects.(6)After retaining structure selection and technical with economic comparison,it is determined that the inner support structure composed of steel sheet piles and steel supports is the best retaining form in line with the engineering characteristics of trench.The numerical model of trench is further established to complete the optimization for structural design parameters,finally the scientific methods of trench for excavation and retaining is discussed based on the spatial effect.