| Micro-pile reinforcement technology is widely used in landslide control and slope support engineering because of its advantages of fast construction speed,simple construction machinery and tools,and small soil disturbance.There are many mountains in southern shaanxi,and landslide disasters happen frequently,among which,most of them are small and shallow landslides.In addition to enhancing the shear strength of the landslide,the miniature piles also play a blocking role on the soil by the continuous retaining structures such as retaining walls.This is due to the structural characteristics of small diameter of pile body and high pile density.This type of pile arrangement can better interact with the pile and soil formed by the soil.The soil arch structure is formed among the piles,and the core anti-sliding body is formed by the interaction of multiple rows of piles.The foundation of the joint action of pile and soil is the generation of soil arch structure between piles.By means of theoretical analysis,model test and numerical simulation,scholars at home and abroad have done a lot of research on the formation mechanism,soil arch shape,stress mechanism and reasonable pile spacing between piles.However,due to the same soil medium around the pile,we cannot see the obvious boundary of the soil arch,so the boundary of pile-soil interaction is not clear,it is a fuzzy artificial boundary.There is no consistent understanding and specification on the range,strength and influencing factors of pile-soil interaction,and there are few studies on the influence of soil expansibility on pile-soil interaction.On the basis of summarizing the previous studies and relying on the example of a landslide control project in mian county,southern shaanxi province,this paper continues the study on the joint action of pile and soil and the soil arch between piles,which plays an important role in clarifying the formation mechanism of the joint action of pile and soil and determining the scope of action.It lays a foundation for simplified design calculation of miniature pile.The main work is as follows:(1)A three-dimensional solid model of the landslide reinforced by three rows of plum-shaped miniature piles is established.According to the numerical simulation results,the interaction between pile and soil is determined within the range of 2 ? 3 times pile diameter in front of pile and 1 times pile diameter in back of pile.The influences of pile spacing,soil shear strength and roughness of contact surface on the interaction range and strength of pile-soil are discussed.The spatiality of pile-soil interaction is proposed,the pile-soil interaction under different buried depths is studied,and the whole process of arch formation,development and destruction between piles is analyzed and described in five stages.(2)the expansion deformation characteristics were tested to study the expansion deformationcharacteristics of the expanded soil in miangxian county.The soil expansive force was measured by the balanced pressure method,which provided the experimental parameter support for the numerical simulation and theoretical analysis.Applying the software thermodynamics module,the influence of swelling on the joint action of pile and soil and the failure mode of soil arch are studied by simulating soil humidification expansion by thermal expansion.(3)according to the research results of numerical simulation,analyze the form and stress form of soil arch between piles,put forward two different failure modes of soil arch under normal working condition and rainfall working condition,and derive the calculation formula of the joint action range of pile and soil.The difference between the calculated result and the simulation result is verified by an example. |
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