Analysis On Pile Supported Embankment With Semi-rigid Reinforced Cushion And Subgrade Stability

This paper is based on the calculation theory and design method of pile supported embankment with semi-rigid reinforced cushion and subgrade stability.Then, the cushion thickness, the bearing capacity of foundation, the foundation settlement of pile-supported semi-rigid embankment with reinforced cushion and the stability of subgrade slope and embankment retaining wall are systematically analyzed and researched. The main work and innovative achievements include:1. A computational formula of cushion thickness, which is comprehensively considering the distinction between different pile diameters, pile spacing, heights of subgrade and reinforcement strength conditions, is established. This formula can replace the existing design method of cushion thickness, which based on the experiential values, hence, improving the scientific and economy of the design of cushion thickness.2. Based on the mechanic action mechanism and influence element of ground bearing capacity on pile-supported reinforced cushion embankment, considering synthetically foundation stiffness, rate of replacement, spreading action of cushion stress, pulling force of geogrid, earth suppress action of side slope, the calculation formula and inspection method were presented considering ground bearing capacity as pile compound foundation capacity under embankment and bearing capacity which is increased by reinforced cushion and earth suppress action of side slope on ground bearing capacity. The results show that ground bearing capacity increases with the decrease of foundation stiffness, the increase ofrate of replacement, geogrid layer number and spreading action of cushion stress. Pulling force of geogrid is a chief element for increasing ground bearing capacity.3. The computational formula of angle during the stability design in clay roadbed is proposed, and then rebuild the table of the angle with higher precise value, improving calculation precision. The analytic formula of the minimum stability coefficient (K min) of potential destructive damage in soft clay subgrade side slope is founded, simplifying the analysis and calculation process of the stability of subgrade slope.4. The new stability design and calculation method,formula method, of the water permeable subgrade is established, by bring in the cohesion and internal friction angle which is a new concept. The formula reflects the corresponding relations among the height, the slope and the soil stability coefficient of subgrade, simplifying the analysis and calculation process of seepage subgrade slope stability.5. Through mechanical analysis, the mechanical effect has been studied on the slope builds layer of rock filled subgrade, stability influence factors are analyzed on rock filled subgrade. The calculation and design method of the filling stone roadbed are established, in order to overcome the roughness and unscientific nature of the original calculation and design method for such type of subgrade.6. The equation for calculating the height of resultant force’s action point, the anti-overturning stability coefficient, and the new design method of anti-overturning stability of the retaining wall are established, which under the condition of nonlinear distribution of earth pressure by using the general static equilibrium analysis. The value of the stability coefficient calculated by the new method is less than the value calculated by the current standard method, therefore there is potential safety risks to use the standard method, which is not consider the nonlinear distribution of earth pressure, to design the coefficient of anti-overturn stability of retaining wall.7. The anti-overturning stability calculation and design method, which has considered the moment of ground reaction force, based on the new definition of retaining wall stability factor against overturning of retaining walls, is established. The coefficient of anti-overturn stability are related to the ultimate bearing capacity of foundation of retaining wall, the anti-overturning stability coefficient rised with the increasing of the ultimate bearing capacity of foundation soil. The value of the stability coefficient calculated by the new method is less than the value calculated by current standard method, so there are safety risks by using the current standard design method which does not consider the ground reaction force moment.The stability design and calculation method of pilled embankment and roadbed with semi-rigid reinforced cushion which is mentioned in this paper, is a supplement and perfection for existed calculate theory and design method. The new methods and new conclusions, which have been worked out in this paper, can be used in the calculation and design in project. It is suggested to use the new methods to review the value calculated by the standard calculation and design method and adjust if necessary in engineering practice.