| The distance between adjacent buildings is getting smaller and smaller due to the tight land use in urban areas,and the design space of foundation pit slope support for later buildings is getting narrower and narrower.Therefore,a detailed analysis of the stress-strain law of the foundation pit support system connected with the adjacent underground structure is of great significance to grasp the new foundation pit engineering stress distribution and damage mode and to guide engineering practice.This paper uses numerical methods to study the stress-strain law of pile-anchor support systems connected to adjacent underground structures in the context of specific projects,and also evaluates the sensitivity of pit support effects to pit design parameters.The main conclusions are as follows.1、Using the adjacent underground garage as an example,the fast Lagrangian difference method was applied to analyse the stress-strain law of the pile-anchored support structure connected with the adjacent underground structures.The results of the study show that: the overall displacement trend of the support piles after the excavation is completed is wavy,with a maximum displacement of 9.02mm;the bottom of the foundation pit rises 11.54mm;the maximum horizontal displacement of the underground garage occurs at the lower part of the side wall of the underground garage,with a maximum horizontal displacement of 0.31mm;in addition,stress concentration occurs in the support structure and the part of the underground garage.In the excavation process,the support structure and underground structure deformation is small,the role of the support system is obvious and the safety is high.2、The study shows that the load generated by the underground garage acts on the lower soil and thus affects the support structure,and there is a certain range of influence of the underground structure on the lower soil,in this paper the influence of the underground garage on the lower soil is about 1 m.Under its influence,the lower soil tends to move more horizontally after the pit is unloaded,which increases the stress-strain at the corresponding position of the supporting pile and has an adverse effect on the support structure.However,the presence of the underground garage also reduces the volume of the soil behind the upper piles of the support structure,thus reducing the deformation of the support piles and the settlement of the soil on the outside of the pit.3 、 This support system,when connected,had a certain impact on the safety of the underground garage.After the excavation was completed the underground garage side walls were deformed the most at the intersection with the bottom slab,and the pillar position was under the most stress,but there was no obvious displacement change or stress concentration at the side wall connection anchors,indicating that the excavation of the foundation pit was causing the underground garage to deform by causing the loss of strata around the underground garage.4、Single factor analysis method is used to analyze the influence degree of single factor such as pile diameter,embedded depth and prestress on the stress-strain law after excavation.The results show that the sensitivity of the maximum displacement of the supporting pile to each parameter is: embedded depth > anchorage structure prestress > diameter of the supporting pile.The sensitivity of the bending moment of the supporting pile to the three parameters is:diameter of the supporting pile > embedded depth > prestress of the anchorage structure. |
