Lime Pile Composite Foundation Method To Deal With Collapsible Loess Foundation Theory And Practice

Lime-soil pile composite foundation is a simple, economical and effective method for treating collapsible loess foundation, which has been wildly used in engineering practices. But the theory study about lime-soil pile composite foundation falls far behind the engineering practice. So, In this paper, the basic behavior of lime-soil and the bearing mechanism of lime-soil pile composite foundation are explored.As has been testified that the emphasis should be the strength (or stiffness) of pile materials to improve the bearing capacity and to reduce settlement of composite foundation. By doing so, the upper load can be transferred by pile to deeper and more spacious subsoil below the foundation. By doing laboratory experiments, the strength of the lime-soil mixture and its factors are studied. At the same time, the engineering properties of lime-loess including compaction shear and compression are analyzed. Results show that lime content affects evidently the engineering properties of lime-loess and water content also is an important factor influencing the engineering properties of lime-loess, and thatcuring time affects compression and shearing property notably. Many parameters such as optimum water content, maximum dry density, maximum cohesion and maximum internal friction angle and their variation rule are reached. Furthermore the variation rule of shear and compression property with the curing time is given. Next, some advice is present for constructor and designer.The actual effect of lime-soil pile composite foundation is studied. Results show that the behavior of pile is enhanced and the collapsibility of the loess between piles is eliminated fundamentally. The compaction effect of artificially drilled lime-soil pile is not obvious comparing test results of soils between piles at different position. Furthermore the shear property of soils between piles is studied.Finally, the behavior of lime-soil pile composite foundation is researched by means of FEM numerical analysis using the basic parameter obtained through laboratory tests. These behaviors include critical length of pile, pile-soil stress ratio, superimposed stress and so on. For lime-soil pile composite foundation under vertical load there is a critical length of pile. The critical length of pile increases with the diameter of pile. Additionally, but the lime-soil ratio and method of drilling hole don't affect the critical length of pile much. The stress concentration in the composite foundation is still significant, and the bearing capacity of the soil between piles is improved. By changing the parameter of pile and soil, the influence of lime-soil ratio and method of drilling hole on the behavior of composite foundation is studied. The conclusion is reached that the lime-soil ratio less affects the superimposed stress and the stress of pile and soil, but which is affected by the means of drilling hole.