Mechanism Research On Open-end Jacked Pipe Pile's Compaction Effect Of Driving Pile

Currently, static pressure pipe pile is widely used in every field of civil engineering fitting. The spreading use of pipe pile is restricted for the effect of driving pile because the effect of driving pile can influence the surrounding environment. Domestic and foreign scholars had done many studys on the effect of driving pile and this paper did some research based on predecessors:1. Through field test, this paper studied the pore water pressure and earth pressure of surrounding soil with pile driving; at the same time, the change law of the pore water pressure and earth pressure corresponding with the distance of pile can be obtained. It also can be learned the effects of holes to relax stress in shielding the effect of driving pile.The conclusion showed that the change is obvious when the distance of pile is less than 5m. Holes to relax stress can sheild 80% of the pore water pressure at the most and it showed that the holes to relax stress can sheild pore water pressure effectively. The earth pressure increased at the first and reduced in the end with the pile driving and when the pile tip reached the embedded depth of earth pressure cell, the earth pressure reached the peak value. At the depth of 6m, the radial earth pressure was mainly composed of the radial effective stress, and the pore water pressure only occupied a small part. The condition was opposite at the depth of 12m.2. Researches were carried out on the plugging effect of jacked prestressed concrete pipe pile for different geological condition. The results shows that a higher plug would be caused for the longer pile with thin shaft jacked into stiffer soil. Open-ended pile prone to act in a plugged mode as penetrate into an underlying weaker layer, while transition from plugged to unplugged penetration appears on reaching a harder layer. The general development of CPT cone tip resistance is similar with that of annulus resistance, and this comparability is independent on incremental filling ratio and penetration depth. The ratio of annulus resistance to cone tip resistance, closely related to geological condition, are approximately 0.6 and 0.8 respectively for soft clay and silt. The observed soil layers distribution in the soil column are somewhat similar to the subsurface condition, except for the convex interface for plug. The test results indicate evident time-effect on shear strength of plug column. Soil is somewhat compressed during the penetration into pile, whereas reduced cohesive strengths is measured probably due to the disturbance. The active plug length appears to be approximately 5-6 times pile diameters in silt, which is 70 percent of total plug length, whereas this value should be lager than 4-diameter in soft clay. This observation is compatible with existing magnitude.3. based on classical spherical cavity expansion theory, this paper derived the analytical solution of pore water pressure,the radial earth pressure and soil horizontal displacement considering the effect of soil plugging effect.