Study On The Application Of Buoyant Pipes To Treat Soft Soils

Soft soil is regarded as with small bearing capacity strength, small compression modulus and commonly occurs excess settlement after the construction. Therefore, it is difficult to control the settlement deformation of soft soils foundation effectively. According to the currently investigation of soft soils, this paper proposed a new application of buoyant pipes after comparing several common treatments on the soft soils. This paper analyzed some related aspects of the new technique, the main investigation contents are as follows:(1) The theory of this new application of buoyant elements to treat soft soils was introduced. The properties of some common pipes used currently were compared, and then the feasibility of treating soft soils with polyvinyl chloride (PVC) pipe was certified.(2) According to the Fick-Henry’s law, the theoretical analysis of water molecules penetration into the PVC polymer was conducted. Then the laboratorial tests on the permeability of PVC pipes were performed. By considering the real civil engineering application, the influence of the pipe’s diameter and thickness on the permeability rate per year was discussed. Due to the threshold value of permeability rate per year was set as0.03%, the optimal dimension determination curves and the fitting curves were presented. It can be used to determine the pipe’s dimension for the practical engineering as a reference.(3) By considering the highway engineering in our country’s the coastal areas, the strength theoretical analysis on the PVC pipe under radial and vertical pressure was conducted. According to the analysis result of σ-δ curve and σ-d curve, the PVC pipe’ sufficient safety performance was certified.(4) By considering the three kinds of complicated stress condition, the mechanical analysis on PVC pipe through a three-dimensional numerical model was conducted. Due to the PVC pipe’s tensile strength and compression strength, the failure wouldn’t occur.(5) By considering the effect of different length of PVC pipe, the compute on soil settlement through a two-dimensional numerical model was conducted after comparing some computing methods of soil settlement.With the length of the columns was in the range of1.0m,2.0m,3.0m and4.0m, the reduced percentage of the vertical displacement on the center of the soil surface were15.7%,30%,40.9%, and48.3%respectively. Meanwhile the reduced percentage of the vertical displacement on the two sides of the soil surface were11.7%,26%,36.9%, and44.3%respectively.