Regional-scale coseismic landslide hazard assessments have traditionally been based on infiniteslope analyses, considering only a single mode of failure. Inventories and landslide reconnaissance work have shown a diverse range of coseismic landslide modes with significantly different consequences of failure. This paper presents a multimodal approach for regional-scale coseismic landslide hazard assessment. Through a two-step procedure, the multimodal method explicitly accounts for four general landslide types commonly observed during earthquakes: rock-slope failures, disrupted soil slides, coherent rotational slides, and lateral spreads. First, the susceptibility to each landslide mode is evaluated based on topography. Second, coseismic landslide hazards are assessed using mode-specific geotechnical models. A trial multimodal landslide assessment is presented for the seismically active country of Lebanon. Results show that the computed coseismic landslide hazard closely matches field-verified slope activity across different regions of the country exhibiting a range of failure modes. These results qualitatively demonstrate the efficacy of the procedure and suggest that multimodal coseismic landslide hazard analysis is especially well-suited for regions with varying terrain and where landslide inventories are not available.

No abstract

No abstract

IntroductionThe main goal of the present study is to make a comprehensive assessment of the existing methods for the dynamic analysis of pile driving, identify the shortcomings and propose improvements. A review of existing shaft and base soil reaction models used in dynamic pile analyses is done to evaluate their effectiveness and identify points that require improvement. Subsequently, we develop improved shaft and base reaction models for use in 1-D dynamic pile analysis. The proposed models are validated using experimental data recorded during driving of field piles and model piles. The procedures currently used by INDOT for the design of axially loaded piles are also examined. For this purpose, interviews were conducted with INDOT engineers and private geotechnical consultants involved in INDOT projects. FindingsThe interviews with INDOT engineers and consultants focused on the methods and procedures presently followed in deep foundation design projects. The methods and the computer software used by private consultants involved in INDOT projects for the design of axially loaded piles are consistent with those used by INDOT's geotechnical engineers. These methods and software follow FHWA guidelines and are in accordance with the standard practice in the U.S. Pile design is mostly based on Standard Penetration test (SPT) data and undrained shear strength measured in unconfined compression tests. Cone penetration tests are rarely performed, although both INDOT and private soil exploration companies have the necessary equipment. Pile drivability calculations and back-calculation of the pile capacity from dynamic test data are done using software that employs Smith-type soil reaction models. Pile driving monitoring and restrike tests are usually performed only in projects whose cost exceeds a certain limit. Static load tests are reserved mostly for research projects.The methods for estimating the unit shaft and base resistances currently used by geotechnical engineers (INDOT or private consultants) have been developed over twenty years ago and have a large empirical content. There has been significant progress regarding methods for the calculation of unit base and shaft resistances. Numerous improved methods that are grounded on the physics and mechanics governing the development of pile resistance have been developed by combining experimental data with analysis. In the case of clayey soils, the differences between the state-of-the-practice methods and the updated methods are not large. In contrast, the formulation of the new methods for piles in sands has important fundamental differences with respect to traditional methods. The new methods for the base resistance in sands use as input either the relative density or the cone resistance directly. The recently developed methods recognize the fact that the limit base resistance is almost equal to the cone penetration resistance and that the ultimate unit base resistance in sands is smaller than the limit unit base resistance. Notably, the equations for β adopted by...