Geocell Gravel Cushion + Gravel Pile Composite Foundation Model Test Research

With the rapid development of freeway construction in our country, the soft subgrade improvement technique changes with each passing day. Geocell is a three dimensional solid reinforcing material which has vast foreground of application, but by far we are lack of its reinforcing mechanism. So under the support of soft subgrade improving project and combining with the item "soft subgrade reinforcing in linchang freeway" the thesis went deep into research of soft subgrade reinforced by geocell gravel mattress +gravel pile composite foundation.First of all under the base of inheriting former conclusions critically, the author probed into the strength properties and load capacity exertion mechanism of geocell mattress, then the similarity rules of the model test "geocell reinforced gravel mattress+gravel pile composite foundation" were deduced by application of similarity theory and the model test was carried out under the guidance of these rules. By analyzing the data gained from the model test the mechanisms of improving load capacity, reducing settlement and asymmetry settlement, the mechanisms of interaction between geocell mattress and gravel pile composite foundation and of improving soil between piles were revealed. And also the cause of high pile-soil stress ratio was pointed out. The author also put forward that the conventional arc failure hypothesis is evidently unreasonable and the failure mode is transformed from penetrating-into failure to side-extruding failure with excessively settlement because of the present of geocell mattress. Aiming at the changing of failure mode the wedge equilibrium method was developed to calculate the stability of soft subgrade reinforced by geocell mattress and the results turned out to be sound. Finally under the plane strain hypothesis the geocell mattress was simplified as limited-long beam placed on Winkler foundation to calculate the settlement and examples were given.