Study On The Foundation Failure Modes And Surrounding Deformation Control Method Under Large Area And Super High Load

With the development of urbanization in China,there are huge quantities of construction waste,causing environmental and social problems.Using the construction to build mountains can make good use of construction wastes and improve the urban environment and landscape,which have great benefits in economic,social and environmental protection.A piled mountain usually covers tens of hectares with a height of 50 meters,the equivalent load on the soil foundation is heavy and greatly outdistances the common construction loads,so the stability of the mountain and foundation must be evaluate and ensured.In addition,piled mountains have a great influence on the surrounding environment,and effective measures should be taken to reduce the impact on the surrounding environment.In this thesis,the foundation failure modes,computation method are studied and corresponding improving engineering measures are advised;the deformation control method by setting up rows of vertical holes around the engineering site is put forward,and the work mechanism,design method and effect of vertical holes are studied,the main research work and innovative achievements are as follows:(1)The conventional formulas of ultimate bearing capacity are established basing on the assumption of uniform rigid load,the applicability on the trapezoid flexible load is studied by finite element approach.The results show that there are difference in plastic zone distribution between the trapezoid flexible load and the equivalent rigid load,but the average settlement of foundation is basically the same,the relationship between load and average settlement(p-s curve)are basically coincide,the ultimate bearing capacity determined by the p-s curve is close to the conventional formulas.So the conventional formulas of ultimate bearing capacity are applicable to the trapezoid flexible load.(2)Large area and super high load engineering has great influence depth,the bearing capacity of each layer needs to be calculated and checked.Model experiment on sand foundation shows that the bearing capacity of sand foundation is much higher than the theoretical value,which can meet the piled mountain requirements if biggish settlement is allowed.But for the saturated clay layer,the bearing capacity calculated by undrained strength parameters,so it is suggested that using plastic drainage plate or sand drain to accelerate consolidation and adopt a reasonable construction design,the construction design method is proposed based on the formula of ultimate bearing capacity and strength growth theory.(3)The determination of the maximum depth which the vertical hole can maintain stable in foundation is a traditional and realistic engineering problem and short of study.In this paper,the planar sliding surface analysis method under plane strain condition is extended to axisymmetric foundation containing vertical cylinder hole,limit equilibrium analysis are carried out,and the relationship between the stable limit depth,the soil properties parameter and geometry parameter.The research results are adopted in the determination of vertical hole stable limit depth in the project case.(4)The design of axisymmetrical vertical hole's supporting structure in both China and abroad is mainly based on the active earth pressure in plane strain problem,which is conservative.The slip line equation in axisymmetric condition is established,and the method of making the active earth pressure to be the maximum value to solve the active earth pressure is proposed.The calculation results show the effectiveness of slurry hole-boring method,and used as design basis for the supporting structure of vertical hole in the project case.(5)The deformation control method by setting up rows of vertical holes around the engineering site is put forward,the effectiveness is verified by coupled infinite element-finite element method and the 3D model of the project case.(6)Slag is a common industrial waste,compaction test,unconfined compressive strength test and expansibility test are carried out on the lime-slag mixed materials with different mix proportions.Results show that lime-slag mixed materials have high strength and small bulk density;it can be used as mat layer in large area and super high load engineering.