Study On The Deformation Characteristics Of Weathered Phyllite Subgrade

For lower strength, the phyllite can be disintegrated and argillitizated under water, and the weathered phyllite subgrade can be easily suffering uneven deformation for a long time.The project aims to study the physical and mechanical properties of the phyllite filling subgrade by the indoor experiment, numerical calculation and theory analysis. It develops the stress and moisture coupling model by accounting for the moisture migration mechanism and the creep characteristic of the phyllite. This study achieved the following results:(1) Through X-ray diffraction experiment and grinding electron microscopy, we analyzed the micro-structure of weathering phyllite and the mineral composition of the rock, and also named it. The result of analyzing the hydrological property showed natural moisture content was low, what’s more, water absorption and swelling property were not obvious. According to the unconfined compressive strength test of original rock of weathering phyllite, it can be maintained that the rock belongs to soft rock. Through the indoor wet-dry cycle test and the relationship between collapse rate and dry-wet cycle times, the chipping resistance of weathering phyllite can be easily analysed.(2) Full weathered phyllite fine grained soil(particle size <0.5mm) was low liquid limit silt(ML), belongs to the poor nature of the roadbed filler. Through the triaxial shear test, we can analyze the variation of weathering phyllite in the condition of urained and undrained consolidation. Combine the indoor standard compaction test and CBR test, the road performance of weathering phyllite as subgrade filling can be analyzed.(3)Through the indoor model experiment with the optimum gradation weathered phyllite filler, we tested the soil deformation under the different water levels and the different loads.The result showed that rising groundwater height was limited, can affect the upper 30 cm range of soil, the saturated water content of each layer has little difference; soil column deformation of external load was more sensitive and maximum deformation with load was almost linear change, and with the groundwater level change slowly; When the ground water was added, the deformation of the soil column lags behind the moisture content of the soil body.(4) Through the numerical simulation of indoor model experiment in applications of Flac3 d, the difference between the test results and the simulation results was small, the overall Change trend was consistent, the overall error did not exceed 10%, the simulated and experimental values was more appropriate, the results verified the reliability of the numerical Flac3 d.(5)Developed the hydraulic coupling model of phyllite roadbed filling, and did the hydraulic numerical simulation of subgrade deformation under the interaction of water, the results showed that as the water table rises, the vertical and horizontal displacement of the embankment were significantly increased; the impact on the vertical displacement was larger than the impact on the horizontal displacement, the shoulder occurred shear failure and tensile failure in the process of calculation.(6) According to the deformation properties of the weathering phyllite subgrade filling,some related improvement measures were put forward from the perspective of waterproof,increase the strength of the roadbed, and later period maintenance, etc.