Study On A Practical Method For Calculating Nonlinear Settlement Of Soft Groud Based On E-p Curve

Increasing number of structures and constructions have to be built on top of soft soilfoundations as a result of the development of the society. The two dominant aspects upon softsoil foundation, settlement and stability, require more and more concerns. It is difficult tocalculate the settlement of soft soil accurately due to the high compressibility, void ratio,water content, sensitivity, low permeability, strength and creep feature of soft soil. Hence, it isof important to develop a practical method being sufficiently accurate for engineeringapplication.Based on the code of foundation engineering in China, the settlement of soft soil isnormally calculated by empirical calibration on one-dimensional settlement analysis based onoedometer test. The correction factor, whichreflects the settlement induced by lateraldeformation of the foundation soil, has a range of1.1to1.7. This is a relatively large range,and it is difficult to be chosen. Hence, reliable and applicable calculation method for thenon-negligible settlement due to lateral deformation is still in need.On this study, the settlement of soft soil is divided into two parts, which are thesettlement resulting from confined stress state and settlement due to horizontal deformationinduced by shear stress in non-confined condition, respectively. The former part of thesettlement is calculated by the conventional layerwise summation method based on the e-pcurve; while the later part is calculated by layerwise summation method with incrementallylinear tangent modulus Et.The concept of the incrementally linear tangent modulus Et on this study originates fromthe e-p curve and Duncan-Chang model. The safety factor method of foundation is used toderive the failure ratio, which is applied to calibrate the unreasonable stress level from elasticsolution. The stress level is calculated based on total stress obtained from the degree ofconsolidation of the foundation; the tangent modulus is influenced by the stress level, whichindicates that the settlement is both affected by loading rate and quantity of loading.Two sample cases of settlement in soft soil are validated by the practical calculation method for incrementally linear settlement of soft soil based on e-p curve; the results arecompared with the data from monitoring, results based on the code method and results fromfinite element method. The comparison shows that the results are close, which proves that thepractical calculation method is applicable and shows its unique advantages.