Research On The Working Characteristics Of The Jet Grouting Anchor Supporting Structure In Loess Foundation Pit

Anchorage technology is widely used in the reinforcement of rock slope,the construction of foundation pit support,underground engineering,and so on.The jet grouting anchor is a new technology in recent years.Compared with the ordinary anchor,the jet grouting anchor has relative advantages.It has higher bearing capacity and larger anchoring force per unit length.It can be applied to a wider range of soil layers,and the quality of the construction is easy to guarantee.However,the research on the jet grouting anchor is very scarce,which shows that the theoretical research lags behind the engineering practice.For this reason,the main work accomplished in this paper are included as follows:(1)The load transfer mechanism and the influence factors of the mechanical properties of the equal section jet grouting anchor and the variable cross-section jet grouting anchor are analyzed by choosing the appropriate shear slip model.Besides,the stiffness formula of cable from specification is provided,and its irrationality is explained.The new stiffness formula of cable is deduced and verified and its influence factors are analyzed.(2)Through field test of anchor cable,standard value of the ultimate cohesive strength,anchoring force per unit length,the interface shear stiffness coefficient,the stiffness and the peak shear strength of the jet grouting anchor are got.The law of development of the plastic displacement is analyzed.The rationality of the load displacement formula is verified.Meanwhile,the stiffness of the common anchor and the jet grouting anchor are compared and shows that the jet grouting anchor does not have the advantage in stiffness.(3)Based on the existing standard method of foundation pit support,combined with the engineering practice,the function and the effect of the jet grouting anchor and the ordinary anchor used in the foundation pit supporting system are contrastive designed.The advantage of the jet grouting anchor is explained.At the same time,jet grouting anchor support system is designed by using the standard stiffness formula and the stiffness formula established in order to illustrate the different influence of support effect.(4)Influence of anchor diameter,cement soil modulus,prestress and distribution on supporting structure are researched with the method of finite element numerical simulation.