Experiment Study And Theoretical Analysis On The Influence For The Rigidity Of The Soil Underneath A Pile To The Pile Shaft Resistance

By a series of tests, the paper researches the changing rules following the pile long-diameter scale for the soil resistance around a no-embedded in rock pile based on their proposed values in Technical Code or Geologic Report. For no-embedded in rock piles, the paper reveals the characteristics of the shaft resistance and the base resistance as follow as the different rigidity of soil underneath a pile and analyzes the laws for the rigidity of soil underneath a pile acting on the shaft resistance. The paper also studies the characteristics of bearing capacity and changing rules when a pile is embedded in different rigidity simulative rock or the cementing degree of the pile and rock is different. An experiential formula of the bearing capacity for the single pile is summarized, which considers the affection for the rigidity of soil underneath a pile to shaft resistance and the exerting rules of the real soil resistance to their values proposed in Technical Code or Geologic Report. By the checking computations on the factual piles, it is proved that not only the bearing capacity for a single pile can be calculated more exactly, but also the division of the shaft resistance and the base resistance is more accorded with the real bearing characteristics of a single pile.Combining this time test with other correlative data, the paper also analyzes the characteristics of bearing capacity for the underside-enlarged pile, points out some questions on its design and application, and gives out a modified formula of the bearing capacity for the underside-enlarged pile.By testing and FEM analyzing, this paper expatiates on the engendering mechanism and causes of the enhancing response for the rigidity of soil underneath a pile to the pile shaft resistance. It answers preferably that why the soil resistance can be brought effectively into play at very small displacement when the distortion of the rock in which a pile is embedded almost does not occur, the slide-destroy circle surrounding a pile end can not be formed. It also explains why the higher the rock rigidity is, the bigger the soil shaft resistance is, and why the distributing of soil shaft resistance for a pile embedded in rock is like a saddle that the value at upside or downside is bigger than that at middle, etc.Based on the enhancing response mechanism for the rigidity of soil underneath a pile, the author puts forward further own comprehension and opinions on the failure model of soil surrounding a pile end considering the concept of therigidity of soil underneath a pile. It can explain preferably the course on displacement to failure of soil around a pile end when the rigidity of soil underneath a pile is different, for example, the soft soil or rock, etc.