Study On Compression Yield Characteristics Of Naturally Sedimentary Structural Clays

The deposition makes the soil form a cemented structure.That makes natural soil different from the remolded soil.The compression yield process of structural soil in engineering is affected by strain rate and loading rate.In this paper,the natural sedimentary soils of Cangshan and Mawei of Fuzhou were selected.Through MSL test,CRS test and CRL test on the natural clay and remolded soil,and the data collected in the literature,the compression yield characteristics of natural sedimentary soil are studied.The influence of strain rate and loading rate on the compression yield characteristics of naturally sedimentary structural clays is discussed.The main contents and results of this paper are as follows:(1)The MSL compression test of undisturbed soil and remolded soil in Cangshan and Mawei of Fuzhou is carried out,and the compression characteristics of undisturbed soil and remolded soil under conventional one dimension loading are analyzed.The compression curves of undisturbed soil and remolded soil obtained from different sample preparation conditions in e-log?'v coordinate system have obvious inflection points,that is,consolidation yield stress(remolded yield stress).The post yield stage of each compression curve can be normalized by using the void index,and the obtained curves coincide with the intrinsic compression curve.(2)The CRS consolidation test and CRL consolidation test are carried out on the remolded soil and the undisturbed soil,and the stress and strain relation,pore pressure characteristics,remolded yield stress(consolidation yield stress),intrinsic compression index and consolidation coefficient are analyzed.The increase of strain rate or loading rate will make the curve move parallel to the right,and the yield curve is basically parallel.The compression index increases with the increase of the vertical effective stress,and remains unchanged after reaching the peak value.The consolidation coefficient increases with the increase of the strain rate or loading rate.With the increase of the vertical average effective stress,the consolidation coefficient decreases gradually and eventually tends to a stable value.For CRS consolidation test,pore pressure increases with increase of strain rate.The increase of strain rate also accelerates the increase of pore pressure.For CRL consolidation test,pore pressure increases with the increase of loading rate,and then decreases after reaching the peak value.(3)Based on the concept of void index proposed by Burland,the compression curves obtained by the CRS consolidation test and the CRL consolidation test can be normalized to intrinsic compression curve with e100*and e1000*in consideration of the rate effects.(4)The curve of CRS consolidation test of Fuzhou undisturbed soil and the data in the literature are analyzed.With the normalization of void index,a set of curves that vary with the strain rate are obtained.Based on the intrinsic compression line of Burland and the model of Liu the curves are analyzed,and a structural compression yield model of naturally sedimentary clays considering strain rate effect is put forward.And the change law of the parameters is analyzed.