Change Law In Stress Distribution In Subsoil And Engineering Properties Of Naturally Structured Clays Under Long Term Embankment Loads

Under the national guidance on supporting the modernization of outdated water infrastructure,the construction of old embankment reinforcement projects in China has been accelerated.The change law in stress distribution in subsoil and engineering properties of naturally structured clays under old embankment are essential for determining embankment stability and continuous settlements.This paper proposes a practical method of determining embankment loads induced vertical superimposed stress in subsoil.Then the extensive laboratory tests are conducted to investigate the difference in compression and hydraulic characteristics and undrained shear strength under long term embankment load.Based on the project of Huaihe River Waterway,the settlement calculation and stability analysis is conducted.The main works are summarized as follows:(1)Note that the traditional stress distribution approach was established based on the assumptions of perfectly flexible loaded area along the base and line elastic theory.A practical method of estimating vertical superimposed stresses in subsoil was proposed with incorporating the effects of contact stress along the base and the elastoplastic behavior of subsoil on load transfer with the particulate-probabilistic theory.The validity of the proposed method was discussed by comparing the calculated settlement of embankments with the field measurements compiled from literature.(2)The physical properties of reconstituted soil sample under different embankment load were measured.A total of 21 oedometer tests were performed on both undisturbed and remolded specimens of natural clays using a modified oedometer apparatus with lower consolidation stress.The quantitative interrelation between the compression behavior and physical index of remolded soil under the embankment load was established.The relationship between the variation of compressibility and soil destructuration was studied.The change law of stress sensitivity of natural clays under long term embankment load was investigated.(3)A total of 21 one dimensional incremental load consolidation hydraulic conductivity tests were performed on both undisturbed and reconstituted clays.Based on these experiment data,the hydraulic behavior of natural soil under long term embankment load were studied.The relationship between the hydraulic conductivity in vertical direction and the compression behavior was investigated,and the key factor affected the hydraulic behavior of natural soil under embankment load was also discussed.(4)A total of 60 triaxial tests by multifunctional GDS triaxial apparatus with high accuracy were performed on both natural and remolded specimens.The relationship between the shear strength behavior and physical index of remolded soil under the embankment load was studied.The variation of undrained shear behavior of natural soil under the embankment load was investigated.The change law of strength sensitivity of natural clays under long term embankment load was established.(5)A model of determining the embankment load-induced settlement in subsoil was proposed,the data compiled from the first-phase project of Huaihe River Waterway verified the proposed model.The finite-element analyses were conducted to simulate natural ground responses induced by embankment reinforcement of the second-phase project of Huaihe River Waterway,and the method of reinforcement was also suggested.