| The soil squeezing effect of static pressure pile is an early research topic.The soil squeezing effect caused by static pressure pile sinking process may have a significant impact on the surrounding environment and engineering.Therefore,it is of great significance to study the soil squeezing effect of large-area static pressure pile and the measures to reduce the soil squeezing effect.Based on the theory of circular hole expansion,this paper simulates the soil extrusion process of static pressure piles by applying volume strain to the pile and applying pile pressure to the pile top,so that the simulated soil displacement field stress field and excess pore water pressure field distribution are more In line with the actual situation,the pile driving process of the single pile can be simulated more realistically.The soil mass is divided by analyzing the disturbance degree of the soil around the pile after extruding the soil.Then,the influence of soil squeeze effect on adjacent existing subway tunnels is analyzed,and the mechanism of pile-soil-tunnel interaction is deeply explored.Then,the influence of pile spacing,pile-tunnel spacing and pile group size under the interaction of pile groups on existing subway tunnels is studied.Influence of structural displacement,according to the difference of pile-tunnel horizontal clear distance,the disturbance range of static pressure piles to adjacent existing tunnels can be divided into strong influence area,general influence area and weak influence area;The subway tunnel shall be constructed within the scope of 2D(D is the diameter of the tunnel),and the construction scope other than 4D shall be selected as far as possible,so as to ensure the safety and stability of the existing subway tunnel structure.The method of merging pile groups is proposed by comparing a large amount of data,which greatly simplifies the calculation of large-area pile groups.The specific impact of the foundation pit in the form of support.The horizontal displacement of the support structure can be effectively reduced regardless of whether the soil squeeze effect is considered or not,and the internal support can effectively reduce the horizontal displacement of the supporting structure.Without considering the soil squeeze effect,the displacement reduction rate of the top of the support is 79.7%.In this case,the displacement reduction rate of the top of the support is 68.1%.At the same time,the reasons for the uplift and deformation of the foundation pit under the condition of soil squeeze are analyzed.Measures are put forward to reduce the soil squeeze effect of static piles,and measures at different stages(before and during pile-pressing construction)are given to ensure the safety of underground structures.The measures taken include setting stress relief holes,setting isolation piles,rationally arranging pile driving sequence and speed,setting up real-time displacement monitoring system and so on.The effect of stress release holes on reducing the soil compaction effect of a single pile is mainly measured by the change of the surface radial displacement and the degree of reduction of the excess pore pressure in the soil.It is found that the setting of stress release holes can greatly reduce the soil compaction effect of a single pile.influence.Isolation piles are used to control the deformation of existing tunnels,not only as a barrier,but also as a certain level of traction.If the control design of the isolation pile is improper,it will directly make the traction effect of the isolation pile far greater than the blocking effect,which is unfavorable to the displacement of the underground project.The length of the isolation pile should be set to 1.5 times the length of the group pile,and the distance between the isolation pile and the tunnel should be as small as possible.The smaller the distance between the two,the better the shielding effect of the isolation pile and the smaller the maximum displacement of the tunnel. |
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