Research On The Settlement Characteristics Of The End Bearing Pile In The Sandy Gravel Stratum

Since the eighty's, China's economy has been growing at a rapid speed.Also for the construction industry ushered in the golden period of rapid development.All kinds of high-rise buildings, large hydraulic structures, high-speed railways, ports and other large and medium-sized construction projects more and more.And the requirements for the foundation bearing capacity of these buildings are more and more strict.Therefore various forms of building foundation and construction technology is also in constant development forward.Because of its high bearing capacity and small settlement, pile foundation is widely used in various types of buildings.With the continuous development of the mechanical industry, rotary drilling rig and a large number of applications in the filling pile project,Because of its fast operation, high construction precision, low noise and other advantages, it is widely used in the pile foundation engineering, in the modern pile foundation engineering to occupy a larger proportion.However, because of rotary drilling rig drilling tool structure characteristics, resulting in rotary drilling bored pile of pile bottom sediment is difficult to clean, it is always difficulty of affecting the bearing capacity of pile foundation.Especially in the chengdu plain region has a wide distribution sandy pebble stratum for rotary drilling operation,the sediment of hole bottom is hard to clean up in place.Due to the pile bottom sediment elastic modulus is small, compression of large, will seriously affect the pile foundation bearing capacity, the work performance of buildings change, lead to engineering accident, affect people's life and property safety.This thesis to spin dig cast-in-place pile end bearing pile of pile bottom sediment defects as the breakthrough point study in sandy cobble stratum end bearing pile sett-ling characteristics. Using MIDAS-GTS finite element numerical simulation software and field static load test, the settlement characteristics of the end bearing pile were an-alyzed systematically.The details are as follows:1. Through the study of the construction process of the end bearing pile, the possible problems and solutions in the process of the drilling of the rotary drilling rig are summarized,and the guiding significance for the construction is provided.2. Through the finite element software midas-gts simulation analysis without pile bottom sediment and different thickness of pile bottom sediment condition, the load on pile top settlement variation, these graphs to visually reflects the sediment defects on the effect of pile bearing capacity. It has a great guiding significance to study the influence of sediment defects on end bearing pile vertical ultimate bearing capacity.3. Considering the pile bottom sediment during compression elastic modulus change,Displacement of pile under different elastic modulus is analyzed.The analysis results show that the reinforcement measures of defective piles of sediment,can effectively reduce the pile top settlement,but this value has a limit, beyond this limit, the effect of the pile top displacement is minimal.4. The existence of the end bearing pile cap can effectively improve the vertical bearing capacity of the pile and reduce the pile top displacement. Therefore, in the construction process of adding a pile cap measures can improve the load capacity of the pile, to ensure the safety of the project.5. Through the field of single pile vertical compressive static load test analysis and software simulation results can be summed up by midas-gts software simulation analysis of the advantages, for end bearing pile vertical bearing capacity detection provides an efficient detection method.