The Finite Element Analysis Of The Mechanism Of DMT And The Application Of DMT On Compaction Control

The Flat Dilatometer Test (DMT) seems to possess most of the preferred qualities of in situ tests, i.e., it is simple, quick, economical, highly reproducible, lowly disturbed and can obtain continuous curves of the sounding. This paper presents an overview of the DMT and of its design applications, in the light of the experience accumulated over the last 20 years. The following applications are discussed: determining common soil parameters, predicting settlements of shallow foundations, compaction control, detecting slip surfaces in clay slopes, predicting the behavior of laterally loaded piles, evaluating sand liquefiability, estimating consolidation/flow coefficients, selecting soil parameters for FEM analyses. The basic differences of the DMT compared to other penetration tests are also discussed.To obtain the knowledge about the test mechanism, a simulation of dilatometer penetration and test process in a "virtual" soil model using the finite element analysis software(ANSYS) are discussed. By modeling the process of membrane's expanding, a more realistic test process is modeled in which the dilatometer is assumed to be rigid and the soil is assumed to be an elastoplastic continuum obeying the bilinear harden criterion. Studies about the disturbance are performed to illustrate the influence of various methods of penetration on the state's change of soil around the bottome of penetrometer.Bringing a simulated but suitable pressure to bear on the membrane, when the certain horizontal displacement of membrane change to 1.1mm, the numeric model of expansion of the membrane has been constructed. The Deformation modulus E from FME and Marchetti introduced formula are compared, and the deference of stress distributing between the result of FEM and Mindlin's solution also is discussed. At last, a correlation between horizontal coefficient of sub-grade and test pressure is given.At the fifth chapter, author introduced the application of DMT techniques to analyze the soil engineering properties of soft expressway foundation synthetically.Combining with the concept and basic theory of "DM" ground improvement method, the mechanism of this method is discussed, and the changes of groundsill's property at different phases are explained. The results archived in this research would provide reference for the application of DMT in domestic geotechnical engineering area.