查看更多>>摘要：Liquefaction triggering of the outcropping 200,000-year-old Ten Mile Hill beds sand facies (Qts) near Charleston, South Carolina is characterized in this paper. The characterization includes evaluating the relative susceptibility to liquefaction of Qts assuming a uniform seismic load and using seismic cone penetration testing at 46 sites, the ratio of measured small-strain shear wave velocity to estimated small-strain shear wave velocity (MEVR), and the liquefaction potential index (LPI). The computed LPI values indicate a slight decrease in the liquefaction susceptibility of Qts moving away (5 to 30 km) from the likely source of the 1886 Charleston earthquake (Mw ~ 7). Also characterized is the liquefaction potential of Qts during the Charleston earthquake and a range of other earthquake loadings. The results for the range of other earthquake loadings are summarized in terms of liquefaction probability curves, which provide a method for mapping liquefaction potential in Qts. A back-calculated, lower-bound diagenesis correction factor of 1.11 for areas of Qts where liquefaction surface manifestations were not observed agrees well with the published data.
查看更多>>摘要：We propose the new continuous slope mass rating (SMR) charts for easy calculation of SMR class of rock slopes in the field. SMR class can be determined by plotting the parallelism between dip directions of slope and discontinuity (slope dip direction and trend direction of intersection line in case of wedge failure) (A) in the x-axis and discontinuity dip amount (βj) (plunge amount in case of wedge failure (βi)) in the y-axis using SMR charts. We apply the proposed SMR charts to an assumed rock slope consisting of four joint sets and a basic Rock Mass Rating (RMRb) value of eighty. SMR class for the assumed rock slope was calculated using proposed SMR charts and by the existing Graphical Slope Mass Rating (GSMR) method. After comparing both the methods, we demonstrate, the proposed SMR charts prove to be simpler and take less time to evaluate SMR class as compared to the GSMR method. The GSMR method requires matching six stereonets for a single rock slope, whereas by using proposed SMR charts minimal use of stereonet is required to calculate trend and plunge of intersection. Proposed SMR charts incorporate the continuous functions (F1, F2, and F3) for SMR calculation, whereas a discrete rating system is used in the GSMR method. This study suggests, the proposed SMR charts are easy to use, more efficient, and can be adopted as a valuable tool for the preliminary rock slope stability assessment in mountainous areas like the Himalayas, where within a few meters joints and slopes geometries changes.
查看更多>>摘要：Typhoon-induced landslides are the primary natural hazard in hilly coastal regions of South East Asia and can potentially devastate coastal communities and infrastructure. They occur at approximately the same time as typhoon strikes, showing complex failure mechanisms under the coupled action of wind, rainfall and trees. Therefore, special assessments should be performed for such geohazards. Here we elucidated the general features of typhoon-induced landslides in southeast coastal China in terms of their geological characteristics, spatial and temporal distribution, and vegetation cover characteristics. We further established a framework to investigate their possible failure mechanisms coupled to wind, rainfall and trees. Specifically, the mechanical response of trees in a typhoon was estimated through a combination of the autoregressive method (AR) and a multi-degree-of-freedom tree swaying model, while the trees and rainfall contributions were determined by calculating the cohesion attributable to roots and the soil shear strength reduction caused by the water content variation. Our results suggest that the root reinforcement disappears when the sliding surface is below the root embedded depth, and the impact of wind load is significant during the slope stability analysis. The Force 14 wind (mean wind velocity up to 45 m/s) reduces the factor of safety (Fs) of the slope by 20% when blowing downhill, and its combined contribution with rainwater infiltration will lead to a higher risk of slope failures (Fs reduction of 45% at the base of the root-soil composite). Additionally, typhoon-induced shallow slope failures are prone to develop at the base of the root-soil composite or the rock-soil interface. Our model results suggest that the impacts of wind and vegetation on the generation of landslides during a typhoon can be significant and deserve more attention in hazard assessment studies.
NSTL
Elsevier