Model Of Interaction Between Pile And Soil&Simplified Calculating Method Of Pile Used To Stability Unstable Slope

As an ancient foundation type, the piles have been applied in civil engineering sinceabout12,000to14,000years ago. So far, the function of piles has various approaches tosupport not only the upper part of the structure, but the vertical load, the combined effect ofhorizontal loads and the moments. Just as for the projects of civil engineering, there arenumerous cases of retaining pile, such as anti-slide pile, retaining pile of foundation pit, pilenearing to heaping load, to withstand the horizontal lateral loads. However, it is not clear forthe bearing behavior of pile, pile-soil interaction mechanism, load transferring law, slopeinstability mechanism. Thus, the working mechanism and design methods of retaining pileremains to be researched further.In this paper, the scope of the study object is limited to the adjacent pile near tofoundation pit and anti-slide pile in an unstable slope. Based on the research ideas of thatcollecting the literature and test data firstly, then doing theoretical model and numericalsimulation, finally implementing the engineering applications, the feature of pile-soilinteraction and calculating method of anti-slide pile used to reinforcement unstable slope arestudied. The innovative research results of this paper are shown as following1. The novel solving methods is put forward for deflection equation of pilesIn order to analyze mechanical mechanism of passive pile-soil interaction in slope, basedon the Winkler elastic model which assumes that soil displacement is elastic, a fourth-ordernon-homogeneous differential equation considering passive pile-soil interaction is presentedto describe the stabilizing pile subjected to an arbitrary profile of residual thrust. Theinhomogeneous term is approached by polynomial and the particular solution of fourth-ordernon-homogeneous differential equation is derived by the recursive method.2. A new instability criterion of slope, displacement mutation ratio, is raised.Based on the curve of field variables-displacement, draw the curve of field variable-displacement mutation rate, which be defined as current analysis step displacement with theprevious analysis step displacement of ratio. When the displacement mutation rate increasessharply, the slope safety factor equals to the corresponding strength reduction factor. Themethod may avoid the uncertainty of human judgment.3. Innovative simplified calculation method of slope stability is established.VBA language, which is be embedded in Microsoft Excel spreadsheet, is programmed toachieve more complex function calculation and computing automation. Then, the stabilityfactor of reinforced slope is solved by the "solver" function of Microsoft Excel. Finally, the pile deflection equation is used to solve the deflection and internal forces of anti-slide pile.4. The sufficient and requirement conditions of optimal anti-slide pile position aredetermined.Learning from the concept of the remaining downward force of the transfer coefficientmethod to draw the remaining force moment curve to determine slope stability region, and itis ensure that the soil mass front the pile remains stability exposed to the load that theanti-slide pile passed downward, which should be the sufficient conditions for the optimalanti-slide pile position. To avoid the soil mass overtopping the pile head, the stability factor,N s, is take as a requirement condition for the optimal pile position.The following conclusions are drawn based on the above innovative achievements,combined with specific engineering parameter analysis.1.The calculations show that the distribution function of residual thrust has large effectson the behavior of anti-slide pile. The triangular distribution forms of residual trust will havethe largest moment of passive piles, followed by a parabola, uniform distribution of thesmallest. Under the same level of subgrade modulus conditions, the uniform distribution ofresidual trust has large displacement of passive piles at the top around the piles than that oftriangle and parabola distribution.2. It shows that the pile deflection and bending moment are obviously affected by soillateral movement model, such as maximum displacements, distribution shapes and center ofgravity, lateral displacements energy which is defined as the area of between the lateral soildisplacement curve with zero longitudinal axis. Along with the increasing of lateral soildisplacement, the pile deflection is increasing and the deflection of pile head is the maximum,the pile moment is also increasing.Uniform distribution of lateral displacement has the same effect on the maximumdeflection and bending moment of the pile. Even if the same lateral displacements energy, thedeflection and bending moment values are increased by up to57%and48%, respectively, andthe location of maximum bending moment has also found a slight upshift, during the lateralsoil movement distribution center is up ward.3. When the soil goes into the state of plastic, the interaction force between pile and soilreaches its maximum value no longer increasing with the increase of the relative displacementbetween pile and soil. So, the elastic method will bring great error due to the behavior ofinteraction between pile and soil is nonlinear,4. Contrasting3D to2D numerical results of safety factor of slope stability, we drew the conclusion that the slope stability safety factor calculated by three-dimensional finite elementmethod is slightly higher than that of the two-dimensional finite element method about2.3%.The priority should be given to the2D finite element model, which has a fast calculationspeed and the results of which could meet the requirements of engineering accuracy in thecase of stability analysis of the conventional plane strain slope. Whilever,3D finite elementmodel are the best choice of the stability analysis on the non-plane strain slope with complexgeological and topography conditions.5. Establishing strength reduction FEM numerical model to analyze the different effectsof anti-slide pile reinforcement position on slope stability. To judge by the value of the slopestability safety coefficient, it will receive maximum value when the anti-slide pile is placed inthe middle of the slope to reinforcement the unstable slope. But, the position of slidingsurface is deep in particularly in the middle part of slope, which will costs much toreinforcement the slope. Considering the economic factors, the optimal pile position cansomewhat shift to the toe of the slope on the premise of ensuring the security.