| Three Gorges Reservoir is one of the regions that landslide is relatively developed. Most of the landslide in reservoir area is located in the sedimentary rock distribution area that sliding bed is layered by composite rock. How to study mechanical characters of anti-sliding piles considering different foundation coefficients to optimize the design of anti-sliding piles is the theoretical problem to be solved in engineering practice.Because foundation coefficient is associated with the physical and mechanical properties of rock mass, and the rules with depth changed is complex. The foundation coefficient is still the hot and difficult problem to discuss in the academic and engineering fields at present.Although the scholars have undertaked a lot of theoretical analysis, physical model test and numerical simulation research for the calculation of anti-slide pile internal force and deformation. Laminar formation of sliding bed is usually regarded as equivalent with homogenate in our current specifications and textbooks. And the research results are not deep enough for considering the influence of different lithologic characteristics of anti-sliding piles of sliding bed.Based on the engineering background of landslide of majiagou zigui, the paper have proposed deflection differential equation of anti-sliding piles considering different foundation coefficient of sliding bed rock mass based on the Winkler foundation model. And the analytical solution is derived and verified its rationality. Meanwhile, the paper has researched the influence of internal force and deformation of anti-slide pile by several kinds of foundation coefficients. Finally, the influence of internal force and deformation of anti-slide piles have researched by the ratio of sliding bed rock, different combinations of lithology, pile section size, embedded depth and the conditions of pile bottom. The main achievements were made as follow:(1) The determination of design parameters of anti-sliding piles, the determination of slide-thrust distribution, the internal force calculation method of anti-sliding piles, the influencing factors of foundation coefficient and the determination method of foundation coefficient were summarized. The study plays an important role in establishing mechanics model and providing some references for the mechanical characters of anti-slide pile.(2) The mechanical model of the elastic anti-sliding piles is builded considering the different foundation coefficient. The formulas of the internal forces and displacement of the elastic anti-sliding piles is deduced considering the different foundation coefficient of sliding bed rock mass. And the calculation processing programs is written in Matlab. The rationality of the theoretical equation was verified by compared with field monitoring data. The method applies not only to single rock mass of sliding bed but also to composite layer rock mass of sliding bed.(3) The different form of foundation coefficient distribution has an effect on mechanical characters of anti-sliding piles. The comparisons of folding line distribution were made with the commonly used rectangular, trapezoidal distribution and a parabolic distribution to show that the maximum values of the bending moment and the shear strength are the maximum. And the implacement of pile tip and the lateral stress of sliding surface are the minimum. Meanwhile, the longitudinal steel to subject bending moment and the stirrups to subject shear force are the maximum for reinforcing design of anti-sliding piles. And the calculating of the implacement of pile tip are accorded with experimental value. Because the broken line distribution is better also to consider the actual distribution of slip bed rock, it is more appropriate to consider the form of the line when sliding bed is layer rock mass.(4) Sliding bed rock mass were generalized into seven conditions according to the composite layered rock mass mechanical properties and distribution properties, namely, soft rock, soft rock-hard rock, the soft and hard with the same amount, hard rock-soft rock and hard rock.The different soft and hard rock thickness ratio of slip bed have changed structural characteristics of sliding bed rock mass and influenced mechanical characters of anti-sliding piles. The greater Layer thickness ratio, the closer the anti-sliding piles stress to homogeneous soft rock characteristics. Meanwhile, the mechanical characters of anti-slide pile are controlled by soft rock mainly. The smaller Layer thickness ratio, the closer the anti-sliding piles stress to homogeneous hard rock characteristics. Meanwhile, the mechanical characters of anti-slide pile are controlled by hard rock mainly. The maximum values of the bending moment of piles and the shear strength of piles decreases gradually and the displacement of piles increases gradually along with the increase of layer thickness ratio. The longitudinal steel to subject bending moment and the stirrups to subject shear force are too large for distributing steel of anti-sliding piles if the slide bed rock mass take into account homogeneous soft rock. And it will cause the waste of engineering. The longitudinal steel to subject bending moment and the stirrups to subject shear force are too small for distributing steel of anti-sliding piles if the slide bed rock mass take into account homogeneous hard rock.And it can not meet the anti-sliding demand. The impacts of mechanical characters of anti-sliding piles were regarded by the layer thickness ratio of sliding bed rock mass in the anti-sliding piles engineering design.(5) The maximum values of the bending moment and the shear strength and displacement of pile body from small to large are hard-soft rock, the soft and hard with the same amount and hard-soft rock under different lithologic combination of sliding bed. And the biggest variations were 5.0%,30.3% and 24.7% respectively. The impacts of mechanical characters of anti-sliding piles were regarded by different lithologic combination of sliding bed in the engineering design of anti-sliding piles.(6) The section size of anti-sliding piles have no effect on bending moment and shear force of pile body above the sliding surface (loading section).The increase vatiations of the maximum values of the bending moment of pile body dip gradually and tends to constant below the sliding surface (anchoring section).And section length was the main factors for affecting the maximum values of the bending moment of pile body. When the pile section size reaches a critical value, the maximum values of shear force of pile body above the critical value showed a trend of increase and decrease below the critical value. Meanwhile, the critical value of maximum shear force of pile body was the minimum. The displacements of pile body decrease gradually and tend to constant with the increase of section size. The section width was the main factors for affecting lateral stress of pile above the sliding surface (loading section). The lateral stress of sliding surface showed a trend of decrease and increase with the increase of section size below the sliding surface (anchoring section).And the lateral stress amplitude increased gradually along the depth of the decreasing.(7) With the increase of anchoring length, the maximum value of bending moment increased gradually, anti-sliding piles reinforcement required the longitudinal steel to subject bending moment increased. And the maximum value of sheat force, lateral stress and displacement of pile tip decreased gradually, anti-sliding piles reinforcement required the longitudinal steel to subject shear force decreased. The maximum value of bending moment and shear force, displacement of piles tip tends to constants with the anchoring length increased. The anchoring length was too long to cause the waste of the economy. Otherwise, it would cause the displacement of pile tip too large and was short of the anti-sliding effectiveness.lt is very important to choose the anchoring length of anti-sliding piles reasonably for designing anti-sliding piles.(8) When the pile bottom was free end, the maximum values of bending moment of pile body was the minimum. And the maximum values of shear force, lateral stress of sliding surfaceand displacements of pile tip were the maximum. Meanwhile, the longitudinal steel to subject bending moment were the minimum and the stirrups to subject shear force were the maximum for reinforcing design of anti-sliding piles. When the pile bottom was fixed end, the maximum values of bending moment of pile body was the maximum. And the maximum values of shear force of pile body, lateral stress of sliding surfaceand displacements of pile tip were the minimum. Meanwhile, the longitudinal steel to subject bending moment were the maximum and the stirrups to subject shear force were the minimum for reinforcing design of anti-sliding piles. When the pile bottom was hinged end, the maximum values of bending moment and shear force, lateral stress and displacement of pile tip lied between the free end and the fixed end. The designer shoud choose anti-slide pile bottom boundary conditions reasonably according to the properties of anti-sliding bed rock mass in the anti-sliding piles engineering design. |
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