The Study On Static Pressure Pipe Pile Bearing Mechanism And Squeezing Effect In Red Clay Geology

The red clay is special property, it is different from general silty clay and sandy soils,but geological distribution of red clay is very extensive in some parts of our country, it is necessary to study the problems of sinking pile and pipe pile bearing mechanism under the red clay geological conditions. Do static load test of silent pipe pile in red clay medium(under hard and below soft) by means of laboratory model tests and granular flow numerical method in this paper, to explore the load-bearing mechanism of static pressure pipe pile in red clay medium. In this paper, the main work and research results are as follows:(1) The indoor model test study on the static pressure pipe pile by self-designed visual model box in red clay geology. To make Q-s curves, pile axial force distributions of pile and side friction distributions of different pile diameters. Considering different pile diameters of static load test in different soil layers, to contrast and analysis tip resistance and pile lateral friction change rule under different working conditions, to reveal load-bearing mechanism of static pressure pile in red clay medium. The results of indoor model test shows, it is different from the pile axial force distribution and the pile side friction peak appear in different depth when the pile tip is located in the different red clay layers, The degree of side friction play a different in different depth, it is can lead to pile shaft floating up after the pile group into the soil, which has a certain influence on bearing capacity of pile foundation.(2) This paper analyses the pile group squeezing effect on the effect on bearing capacity of pile foundation through an engineering example. Field static load test shows that static pressure large pipe pile can lead to pile foundation bearing capacity to reduce about 40% in red clay geology, the pile foundation bearing capacity has been greatly increased after re-pressing.(3) On the basis of the indoor model test, applying PFC2 D particles flow of numerical method to simulate the pipe pile static load test in the red clay medium(layered medium), to establish a reasonable particles flow numerical simulation model of pipe pile,to study the change rule of the macro mesoscopic parameters in the process of the pipe pile static load by the method of particle flow, it can make up for the shortage of the existing measurement equipment, to reveal the macro evolution of mesoscopic mechanism of the soil in the process of pile driving. The particles flow of numerical method of the research results show that the horizontal displacement decreases with the increasing of the distance to the pile axis in the process of pile driving, the main scope of influence is about 7 times pile diameter; Pile tip stress is much larger than the pile lateral stress;The pile tip soil porosity is reduced in the process of pile driving, compactness and number of average contact is increasing; The pile lateral soil porosity and sliding ratio is increases,compactness and number of average contact is reducing; It can be seen from the feature points of trajectory, the soil has different trajectories in different depth when pile grouppress-in the soil, a certain depth below the soil downward movement to squeeze the dense,but above the depth of the soil upward movement to float.