Optimization Design And Safety Factor Calculation Of The Slopes Reinforced By Pre-stressed Anchors And Lattice Beams

For recent years, with the development of Chinese economy and the enlargement of construction of infrastructure such as transportation, water conservancy and mining engineering, the landslide has been becoming more and more serious. The measures of prevention and controlling landslide are also highly regarded. The measure of lattice beams with pre-stressed anchor cables is a new method for landslide hazard prevention and control and widely applied in practical projects. The pre-stressed anchors and lattice beams system combines anchoring of anchors and retaining of lattice beams, so it could not only reinforce deep layer soil, but also prevent weathering of shallow rock and erosion of soil with slope protection. However, the studies on optimization design of lattice beams with pre-stressed anchors, the stress distribution law in the slope and the safety factor calculation of the slopes after reinforcement are very rare. Therefore, the study on lattice beams with pre-stressed anchors has great sense.In order to optimize the design of pre-stressed anchor and lattice beams in the slope reinforcement, and calculate the internal force and displacement of the beams, the lattice beams are considered as ground beams which subject to concentrated load of the anchors on two-parameter elastic foundation, and the initial parameter method is deduced in this paper. According to the calculation of bending moment of lattice beams with two-parameter elastic foundation in some slope reinforcement project, we compare the results with the results calculated with Winkler elastic foundation model and the data measured in the field test. The comparison shows that the results calculated with two-parameter elastic foundation model are smaller than that calculated with Winkler model, but closer to the data measured in the field test. It means that the two parameter elastic foundation model is more reasonable than Winkler elastic foundation model in the calculation of internal force and displacement of lattice beams. Finally, we analyzed the influence of beam flexural rigidity El and two parameters of the ground k and G on sub grade reaction, bending moment and shearing force of the beams.According to the initial parameter method of Pasternak two-parameter model, we take the beam flexural rigidity El and two parameters of the ground k and G into consideration to reveal the reaction force distribution laws of the beams using the solution of Pasternak two-parameter elastic foundation beam when the anchor interval and the cantilever length vary. Reasonable range of cable interval and cantilever length is obtained according to the distribution laws of reaction force.In order to study the additional force distribution law in the slopes reinforced by pre-stressed anchor cables and lattice beams, optimization safety factor calculation method of slopes after reinforcement, the load applied by anchors via lattice beams is transformed as line load on the slope, and theoretical solution of additional stress and displacement in the slope could be obtained by means of elastic theory. With parameter of some slope, we get the additional stress distribution by using theoretical solution. According to the distribution of the additional stress, we get new safety factor formula of the slopes after reinforcement which takes the function of lattice beams on stress dispersion into account. The safety factors are obtained by means of the FEM method, the traditional method and modified method deduced in this paper separately, and comparative analysis is made at last. The results manifest that the modified method gets a smaller, but more reasonable safety factor than the traditional one.