Research Of The Function Mechanism And Analysis Of Force On The Facing For Combined Supporting Consisted Of Soil-nailing Wall And Micro-Piles

The micro-piles composite soil-nailing, a common and effective method of composite soil-nailing, combines soil-nailing with micro-piles.This supporting system has many advantages, such as convenient construction, short construction period and the low project cost. Through this method, the deformation of the foundation excavation can be effectively controlled, and the stability of slope can be improved.At present, the research on the interaction mechanism of this supporting method is not plenitudinous, and there is a lack of the field test data. Although the technical support widely used, this method does not have formed integrated theoretical system yet. In this paper, we will use the finite difference software FLAC, through the comprehensive simulation and analysis of the excavation process of the pit with the micro-piles composite soil-nailing wall supporting, aimed at doing more further in revealing the internal forces and deformation characteristics of the supporting method, so as to provide a scientific basis for designing and the construction of this supporting method.In this paper, the development, research and prospects of application of composite soil-nailing are summarized, the deficiency of present research on the technique is presented, and the mechanism of the composite soil-nailing is analyzed and explained, moreover, the stress model of the facing of the composite soil-nailing wall is established. Based on the analysis and the comparison of the simulation result, this paper makes some research on the mechanism of the facing of the soil-nailing. The results show that:â‘ The soil-nailing has an excavation effect, that is, all the soil nails have been set up are affected by the subsequent pit excavation.â‘¡The maximum horizontal displacement of the excavation pit appears at the middle depth or lower of the pit, where the axial force of the soil nail and the moment of the facing also be the max, usually.â‘¢Inside the supporting system, the supporting facing can effectively reduce the horizontal displacement of the excavation, balance the soil stress disturbed by the soil excavation and transfer the larger axial force from the upper soil nail to the lower ones, aroused by the larger deformation because of the soil excavation. The facing can fully display the potential utility of each soil nail, and adjust their axial force, but plays little role in limiting the vertical displacement of the soil near the excavation.â‘£Inside the micro-piles composited soil-nailing, the facing can be simplified to be a thin board with two opposite edges simply supported. The thin board sustains the moment and shear force induced by the soil nail concentrated force and the lateral soil pressure, presents a bending deformation.