Force and deformation characteristics of double-row miniature pile-anchor-support combination support structure for deep foundation pit
In order to study the evolution of force and deformation of miniature pile-anchor-support structure with excavation of deep miscellaneous soil,firstly,in-situ test of double-row miniature pile-anchor-support was conducted based on a deep foundation pit project in Qingdao to analyze the distribution of pile moment of front and rear piles under excavation conditions.Secondly,combined with ABAQUS finite element simulation method,the synergy effects between miniature pile,prestressed anchor cable and steel support and the deformation of foundation pit were clarified.Finally,the influence mechanism of miniature pile diameter change and support structures on pile force and foundation pit deformation were revealed.The results show that the increase of excavation depth causes the pile positive and negative bending moment to increase continuously,the extreme point position shifts downward,and the overall pile bending moment is a positive"S"shape distribution.Excavation to the bottom,the pile reverse bending points of the front row of piles are located 0.5 m below the steel support and the location of the excavation surface,and the pile reverse bending points of the back row of piles are located 0.5 m below the steel support and within 1.0 m below the excavation surface.The vertical influence range of foundation pit excavation is about 1.35H(H is the depth of foundation pit excavation).The pile diameter is nearly doubled,but the soil horizontal displacement only decreases by about 51%,and it is not significant to limit the deformation of the foundation pit with the pile diameter continuing to increase.Compared to the pile-anchor support structure,under the action of pile-anchor-support structure,the maximum horizontal displacement of the front and rear row piles decreases by 34.9%and 27.3%,respectively,and the maximum horizontal displacement of the excavation soil decreases by 46.0%.
deep foundation pitsmicro pileanchor cablessteel supportsin situ testingfinite element simulation
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