Effect And Applicability Of Anchor Support System In Soft Soil Foundation Pit

With the rapid development of urban construction and technology of civil engineering,technology of anchor-support get unparalleled development since the turn of last century,technology of soil anchor support has gained more application in foundation pit excavation due to its advantages.At present,anchorage force of anchor support system in the foundation pit is usually designed on the assumption that the prestressing force of anchor after tension doesn't change during the subsequent construction process,however,in the actual project,Construction disturbance will inevitably cause displacement of anchor head and anchor end,which will cause the change of prestress and affect the stability of foundation pit support.Based on the above background,this paper makes use of theoretical analysis,numerical simulation and other methods to study the structure form,stress characteristics and the change of anchor prestress during construction of foundation pit soil anchor cable support system.the main work of this paper is as follows:1.The anchor structure and classification of foundation pit anchor are expounded,the bearing capacity and ultimate stress of anchor system is also analyzed in this paper.This paper study the stress distribution of anchor axial force through elasticity theory solution and numerical solution,the result shows that the axial force of anchor decreases along the anchorage length and doesn't change during the free section.The load of the anchor head will change when displacement occurs in the anchor,the axial force and distribution of the anchor will also change.2.The paper deduces the existing calculation method of anchor force in the foundation pit with anchor support system and analyzes itsrationality.The paper simulates the foundation pit supported by prestressed anchor with numerical analysis software FLAC3 D.The result shows the displacement of anchor head and anchorage end occurs in the same direction constantly during the construction of the foundation pit,then the size of the prestress is constantly changing,especially when the next anchor is tensioned,the loss is the greatest.On this basis,the influences of elastic modulus of soil,insert of pipe,diameter of anchor bar,anchor angel,length of anchorage section on the change of prestressing force of anchor during construction are analyzed.3.Through the establishment of three-dimensional foundation pit model based on the actual project,the paper analyzes the anchor prestress at the midpoint of the long side of the pit,the midpoint of the short side,the midpoint of the short side of the pit,the quarter of the pit.The result show that the prestress of anchor has a "spatial effect" with the change of construction process,and the prestressed loss of anchor is more serious at the foundation corner.