| Geotechnical slope failure has always been one of the major disasters witch encounters in geotechnical engineering construction. The correct evaluation of the slope stability, nip in the bud, is important to ensure the security of production and construction and people’s property. As new supporting structures, prestressed anchor supporting structure, frame with prestressed anchor supporting structure and soil nail composite prestressed anchor supporting structure have been widely used in geotechnical engineering. But at present, there are still many problems on many theories and applications about thus three supporting structures. This paper is based on the National Science and Technology Support Project:Landslide and Debris Flow Projects Prevention Technology Research and Demonstration in Bailong River Basin (2011BAK12B07). The stability analysis method about slope supported by prestressed anchor, frame with prestressed anchor and soil nail composite anchor is studied combined with practical engineering. The main work and conclusion gained are listed as follows:(1) First of all, based on the circular sliding failure of slope, according to limit equilibrium theory and slice method, the slope stability analysis model was established under the effect of additional stress, and then the safety factor calculation formula was given. Then, anchor prestress was considered as a concentrated force, according to the stress calculating method for the half plane body boundary with the effect of normal concentration, the additional stress caused by prestress in the slope supported was estimated. The effect of anchor prestress was turn to additional stress, then the safety factor of slope supported by prestressed anchor was calculated by using the safety factor calculation formula under the effect of additional stress. The stability analysis and calculation of slope supported by anchors with prestress was achieved. The most dangerous sliding surface search was realized by MATLAB programming, the programming also provides a visualization output for the calculation result. Comparative analysis for the effects on the stability with the additional stress components, the prestress value and the anchor arrangement of the supporting structures were carried out by the numerical simulation and engineering examples. The rationality of the method in this paper was verified.(2)Analyzed the mechanism of frame supporting structure with prestressed anchor, based on the circular sliding failure of slope, treated the frame and sliding zone as a whole rigid body, the stable zone as an elastic foundation, and the prestress as concentrated force on the rigid body, calculated the reaction on the slip body from elastic foundation. According to limit equilibrium theory and slice method, a simplified model for stability analysis of frame supporting slope with prestressed anchor was given. The most dangerous sliding surface search was realized through MATLAB programming, the programming also provides a visualization output for the calculation result. The applicability of the method in this paper was verified, through engineering examples and comparing to slope analysis software. The rationality was verified through testing the performance, anchor axial force, and frame displacement of the frame supporting structure with prestressed anchor.(3)The mechanism and performance of soil nailing wall composite prestressed anchor were deep analyzed through numerical simulation. The follow conclusion were drawn:1) Horizontal displacement of foundation pit was limited effectively by adding prestressed anchors to the soil nailing wall, in comparison, the vertical displacement was limited weakly.2) After anchor install completed, the axial force of completed soil reduced and the axial force of succedent completed soil nails was limited with increasing slowly. A foundation pit was monitored, and the conclusion from numerical simulation was verified.(4)According to the conclusion drawn by the numerical simulation and monitoring of the soil nailing wall composite anchor, divided the roles of anchor and soil nails. Treated the soil nails in the zone near the prestressed anchor as safety reserve, the role of them was ignored in stability analysis. The soil in the zone was strengthened by the prestress. The method for stability analysis of soil nailing wall and slope supported with prestressed anchor combined together to establish the model of soil nailing wall composite anchor. Then the safety factor calculation formula was given, the roles of anchor prestress and soil nails were both considered in this method, so, quantitative result was given in stability analysis of soil nailing wall composite anchor. The most dangerous sliding surface search was realized through MATLAB programming, the programming also provides a visualization output for the calculation result. The applicability of the method in this paper was verified by engineering examples. |
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