Passive Soil-arch Effect In Front Of Embedded Section Of Anti-slide Piles And Its Influence On The Force Of The Piles

Prevention and control of landslides is one of the most critically vital geological hazards.Due to the mutual influence of adjacent cantilever rectangular anti-slide piles,the additional stress in the soil in the passive area in front of the piles will affect and superimpose each other during the transmission of landslide thrust,resulting in the "arch effect".Existing guidelines and regulations for the design of anti-slide piles do not,however,account for the role of passive soil arch effect on pile spacing and pile bearing capacity.Current study on the passive soil arch effect in front of the embedded part of anti-slide piles is insufficient,as is research on the calculation of the antislide pile’s force capacity by passive soil arch in front of the piles.The research on the passive soil arch effect in front of anti-slide piles will enhance the pile foundation calculation theory and have significant application value for the design,calculation,and engineering practice of cantilever anti-slide piles in the western Loess region.This article is based on the National Natural Science Foundation of China project "Formation Mechanism and Evolution process of passive soil arch in front of cantilevered rectangular anti-slide pile embedded section in Loess Region"(No.41877285).The formation mechanism,evolution process,intermorphism,and influencing factors of passive soil arch in front of fixed section of anti-slide piles were investigated using the oretical analysis,model testing,and numerical simulation.The force calculation theory of anti-slide piles including the passive soil arch effect in front of piles is proposed based on the modified strain wedge model of pile row.The primary research findings and conclusions are as detailed below:(1)The existence of a passive soil arch in front of piles is demonstrated.The passive soil arch generated in front of the piles as a result of nearby pile-soil interaction,which deflects the major stress direction of the soil in front of the piles.In accordance with the reasonable arch axis theory,a numerical determination method of soil arch axis is proposed,as well as physical determination methods for soil arch thickness t and arch axis height f.When the ratio of pile spacing to pile width,L/a = 3~4,the passive soil arch effect is evident.(2)Model experiments of embedded section of anti-slide piles with pile spacing of 3 times pile width(L = 3a)and 4 times pile width(L = 4a)were used to study th e creation,evolution,and three-dimensional geometry of passive soil arch in front of piles.The results indicate that the evolution process of a passive soil arch can be roughly split into four stages: formation,development,completion,and failure.Arch to span ratio of passive soil in front of pile grows with increasing relative displacement of pile and soil,but arch to span ratio of passive soil in the completion stage falls progressively with increasing burial depth.As the loading amount increases,the arch of passive soil in front of the pile gradually forms and deteriorates along the buried depth,and the three-dimensional surface produced by the arch of passive soil gradually probes downward along the buried depth.Concurrently,the whole moves to the loading direction.(3)Study the sagittal ratio S and relative soil arch thickness t’ of passive soil arch in front of the embedded section of anti-slide pile through the DC-MC constitutive model of unsaturated undisturbed loess in secondary development.The results indicate that when pile-soil relative displacement increases,S falls,then increases,and eventually tends to stabilize.The final span ratio falls as pile spacing increases.With different pile spacing,the final span ratio shows different distribution law with buried depth.t’ initially increases and then drops with the relative displacement of pile and soil,and then tends to stabilize and gradually increases as pile spacing increases.Under the same pile spacing,the final relative soil arch thickness of each buried depth can be reg arded as the same.(4)For typical loess locations,a strain wedge calculation model of a single pile is proposed,which is more accurate than the power series method when the load is substantial.On this basis,the passive soil arch effect in front of the pile is taken into a ccount,and a modified strain wedge calculation model of pile row is developed.It is more accurate than the "m" method and the unmodified strain wedge calculation method at capturing the mechanical properties of the embedded section of anti-sliding row piles in loess sites.The embedded section of anti-slide pile force analysis theory is improved.