Landslide stability analysis increasingly utilises high-resolution coupled hydrology–slope stability models (CHASM) to improve stability assessments in areas subject to dynamic pore pressure regimes. In such environments, the estimation of soil hydraulic conductivity (K) is a key parameter but one which is not always readily available or determined with the required resolution. By using basic soil particle-size distribution (PSD) data, we evaluate the microscopic composition of the actual soil, and applying the analytical relations obtain by a Self-Consistent Method (SCM) approach, we determine an appropriate value of K. This is of importance in that it allows within-soil type variability to be reflected in terms of K and hence within the model structure. The SCM methodology is briefly reviewed and an illustrative application is undertaken for a slope typical of Hong Kong. The results show model output sensitivity in terms of moisture content and factor of safety (FOS) when comparing K values determined using the SCM approach and the conventional field determination. In attempting to determine slope hydrological processes and attendant stability conditions, we conclude that the application of SCM approach offers a novel methodology for potentially improving the parameterisation of hydrology–slope stability models. 相似文献
Recent laboratory and field experiments have confirmed that sand does indeed exhibit time-dependent behaviour. Based on these
findings, it was considered necessary to revisit some of the published experimental results on the static liquefaction phenomenon
of loose anisotropic Hostun RF sand. Time-dependency might have had a significant influence on the observed undrained response
of anisotropic consolidated sand specimens. Specific triaxial tests have been performed and a qualitative analysis is presented
in this paper. It is shown that, despite the differences on the anisotropic consolidation path employed, different specimens
show qualitatively identical undrained responses if creep periods are performed at identical test stages or if the anisotropic
consolidation takes place very slowly. With time, the undrained stiffness and strength are considerably improved and this
may explain why the static liquefaction phenomenon is not as common in practice as could be predicted based on an instability
line concept. Whereas the original instability line concept was developed independently of time-dependency, in field situations,
the liquefaction resistance of the sand can increase with time. 相似文献
AbstractThe aim of this study was to understand seasonal variations in the vertical structure of the water column, and to quantify the importance of the physical forces (solar radiation, wind and hydraulic retention time) that control mixing processes in a reservoir bordering the Pantanal floodplain. Samples were taken every three months in the reservoir centre, at four depths, for the measurement of nine physical and chemical water quality parameters. The reservoir presented a long stratification period with complete mixing in winter. The vertical structure showed that, during the stratification period, the upper layers of the reservoir are homogeneous and the physical and chemical composition only changes at greater depths. The wind acting over an extended period is the only factor that significantly influences the vertical structure in the reservoir, giving rise to mixing processes. Moreover, the position of the draw-off point in the upper layer of the reservoir, together with the reservoir depth, enhances vertical stability. 相似文献
A new constitutive model for fibre-reinforced cohesive soil is proposed. The model combines a Cam-Clay like bounding surface model with an elastic–plastic one-dimensional fibrous element model. A “smearing procedure”, which can consider any spatial distribution of fibre orientation, is employed to transform discrete tensile forces developed in the fibres into stresses for the composite material. The fibre stress contribution is bounded by both degradation of soil–fibre bonding due to pull-out mechanism and tensile strength of the fibres. Eventual occurrence of fibre breakage is also considered. The model performances are analysed for both consolidation and shearing loading modes, and qualitative comparison is performed with experimental data available in the literature. For consolidation loading, tensile stresses are not developed in the fibres and thus the fibre effect is rather limited. For drained shear loading, addition of fibres can result in a consistent shear strength increase. The beneficial effect of fibres seems to be controlled by two parameters: the fibre tensile stiffness and the fibre/soil strain ratio that accounts for any possible slippage or shear deformation at the fibre/soil matrix interface. For undrained shear loading, the strengthening effect of the fibres appears to be counteracted by the increase in pore water pressure, induced by the additional confining contribution of the fibres. In agreement with published experimental data, the model suggests also that the moisture content is a key factor governing fibre effectiveness for undrained shearing. Finally, analysis of the model predicted critical states for fibre-reinforced cohesive soil is provided. 相似文献
Chalk breaks easily when subjected to human action such as mechanical handling, earthworks operations or pile installation. These actions break the cemented structure of chalk, which turns into a degraded material known as putty, with lower strength and stiffness than the intact chalk. The addition of Portland cement can improve the behaviour of chalk putties. Yet, there are no studies determining the tensile strength of chalk putty–cement blends, the initial stiffness evolution during the curing time and other design parameters such as friction angle and cohesion of this material. This paper addresses this knowledge gap and provides an interpretation of new experimental results based on the dimensionless index expressed as the ratio between porosity and volumetric content of cement (η/Civ) or its exponential modification (η/Civa). This index aids the selection of the amount of cement and density for key design parameters of compacted chalk putty–cement blends required in geotechnical engineering projects such as road foundations and pavements, embankments, and also bored concrete pile foundations.