Experimental Study On Assembly Type Recyclable Soil Nailing And Skin Friction Of Pile Foundation On Broken Bedrock

In order to adapt to the architectural trend of industrialization,to overcome the shortcomings such as temporary waste of soil nailing supporting of foundation pit,the pollution of geological environment and the development of underground space is influenced,an assembly type recyclable soil nail foundation pit supporting structure is developed,and the field bearing capacity test is completed.In addition,in view of the present situation of the lack of the calculation method of the bearing capacity of the pile foundation in the broken bedrock area,the physical model test method of rock breaking degree is constructed,and the direct shear test of broken bedrock model and pile concrete is completed.Based on the above experiments,the following conclusions are obtained by applying theoretical analysis and numerical simulation:(1)Experimental study on assembly type recyclable soil nailing? Through field test and numerical simulation,it is concluded that the mechanical mechanism of the assembly type recyclable soil nail is different from that of traditional grouting soil nail,the pull-out force is provided by the ultimate friction resistance between soil nails and soil and the wire end bearing capacity,and the pull-out force of the end is proportional to the friction resistance and inversely proportional to the wire end bearing.In the limit state,the maximum proportion of the friction resistance between soil nails and soil is reached,and the minimum proportion of wire end bearing capacity is reached.? The optimal structure of the assembly type recyclable soil nail is the diameter of the rod body with a diameter of 2?3 times,the diameter of the rod diameter of 0.3?0.45 times.? The formula for estimating the bearing capacity of the assembly type recyclable soil is put forward,and it is verified by engineering application.(2)Experimental study on physical model of broken degree of bedrock and pile side resistance? The method of modular concrete simulated crushing bedrock is proposed,and the integrity index test of different integrity bedrock physical models is completed.? A special equipment is developed to complete the shear test of the fractured bedrock physical model and pile concrete cementation,proving that the shear strength of the fractured bedrock and the intact bedrock was close to the shear strength of the pile.? According to test data,fitting formulas for calculating the frictional resistance between pile and broken rock,through the comparison and analysis of engineering case,get in under the geological conditions of the case,in the artificial dig-hole pile load on the bedrock broken characters for end bearing friction pile.It is suggested that the design of foundation pile foundation of broken bedrock should not be treated blindly as end bearing pile,and it is necessary to take into consideration the situation of overburden rock soil layer and pile hole roughness.