Study On Deformation Of Prestressed Anchor Composite Soil Nailing Wall Flexible Supporting Structure

The prestressed anchor composite soil nailing wall is widely used in the foundation pit support engineering because of its simple construction and low cost advantages.However,there is relatively little research on its deformation,and it has not yet formed a complete theoretical system.Based on the former researches in both domestic and abroad,this paper establishes a model of the prestressed anchor composite soil nailing wall and other flexible supporting structure,and puts forward the calculation method of horizontal displacement and settlement deformation.The influence factors of deformation are also analyzed.Specific studies and achievements are as follows:First of all,in order to study the horizontal displacement of prestressed anchor composite soil nailing wall flexible supporting structure,by considering the anti displacement ability of soil,the soil was simplified as a continuous distribution of numerous soil spring model,and considering the spring stiffness of soil is reduced with the plastic development of soil.Based on the assumption that foundation pit lateral earth pressure is shared by the soil,soil nail and prestressed anchor according to size of stiffness,and the assumption of prestressed in the form of outside load function to the soil,the calculation method of the horizontal displacement under the action of the soil pressure,the prestress and the ground overload is obtained.Secondly,in order to study the settlement deformation of prestressed anchor composite soil nailing wall flexible supporting structure,the change of the stress field caused by the excavation of the soil was analyzed.By simplifying the soil body into a series of compression springs model group with stress dissipation device,the law of horizontal stress attenuation was obtained.It is found that the decrease of horizontal stress is the main factor that causes the excavation settlement by analyzing the plane stress state of any point.And the stiffness of the supporting structure also has some influence on the settlement mode.For prestressed anchor composite soil nailing wall,the settlement deformation of this flexible supporting structure can be estimated by neglecting the stiffness of supporting structure.Finally,by using the finite difference software FLAC3 D,the factors that affect the deformation of prestressed anchor composite soil nailing wall flexible supporting structure from three aspects of soil parameters,soil nails and prestressed anchor were analyzed.Moreover,some results were obtained.Two approaches,the given method in this study and software simulation,were used to calculate the same practical project.The results show that the horizontal displacement and settlement deformation of the two methods are basically the same.The methods above are reasonable and can provide guidance for similar projects.