Abstract

This paper presents a detailed numerical study of the retrogressive failure of

landslides in sensitive clays. The dynamic modelling of the landslides is carried

out using a novel continuum approach, the particle finite element method,

complemented with an elastoviscoplastic constitutive model. The multiwedge

failure mode in the collapse is captured successfully, and the multiple retrogressive

failures that have been widely observed in landslides in sensitive clays

are reproduced with the failure mechanism, the kinematics, and the deposition

being discussed in detail. Special attention has been paid to the role of the clay

sensitivity on each retrogressive failure as well as on the final retrogression distance

and the final run‐ out distance via parametric studies. Moreover, the

effects of the viscosity of sensitive clays on the failure are also investigated

for different clay sensitivities.

Abstract

This article presents an overview of landslide investigation in Puerto Rico from the time of Spanish control until the present.  In addition, a projection for future developments is offered.  The island’s tectonic and geographic situation combined with a history of intense agriculture practices yield a predisposition of landslide hazard.  Mass wasting manifests itself in several modalities with shallow soil failures being most common and deep bedrock slides being most destructive.  Movements can be provoked by seismic activity but are regularly triggered by high-intensity rainfall events associated with tropical cyclone systems. Advances in landslides science made during the latter 20^th century were made possible by earlier topographic and geologic mapping efforts by the United States Geologic Survey. In the 21^st century, instrumentation and monitoring endeavors have been made more effective with the use of emerging technologies.  In the near future, advanced real time systems and forecasting programs are possible, and the continued investigation of landslides as principal agents of erosion will lead to a more focused understanding of surficial processes over geologic time.  In a landscape faced with natural disasters, it is necessary to meet these phenomena with an adequate level of commitment in order to mold a more resilient society. 

Abstract

Hurricane María was an extreme atmospheric event that impacted Puerto Rico in 2017. As a result of the passage of hurricane María over the island more than 70,000 landslides were triggered, with the highest density of mass wasting found in the mountainous center of the island. This area is highly susceptible to slope failure given the local soils that form as a result of continuous tropical chemical weathering of the bedrock material. Copious amounts of sediment from these soils were mobilized and transported by the landslide-triggering event. The results of our study reveal the soil types that are most susceptible to mass wasting loss in order to better understand their susceptibility to failure and contribution to sedimentation across the rugged interior of the island. A preliminary analysis of area volume scaling statistics for thousands of landslide sites in the important Lago Dos Bocas basin reveals that Hurricane María likely liberated at least 1.7 million cubic meters of mostly superficial sediment in the lake’s contributing area (not including the Caonillas sub-basin). In an effort to determine the efficiency of the fluvial system to transport these sediments during and after the catastrophic hurricane event, bathymetric surveying was carried out in Lago Dos Bocas, where much of the sediment is hypothesized to have been deposited. This reservoir is a vital piece of infrastructure in the island as it supplies water to the San Juan metropolitan area. Based on the 2021 bathymetric survey and the historical data, the excess sediment deposition to the reservoir related to Hurricane María is estimated at approximately 2.1 million cubic meters. When compared with data from 1999-2010, this volume represents the equivalent of 18 years of background sedimentation. At present, the reservoir capacity loss since construction is at 64%. These analyses are pertinent to understand how the local sediment budget has been affected and to re-calculate the useful life of the reservoir and highlight the vulnerability of Caribbean infrastructure systems, given the forecasted likelihood of increased tropical cyclone activity in the years to come. 

Abstract

We present an approach for the simulation of landslides using the Particle Finite Element Method of the second generation. In this work, the multiphase nature (granular phase and water) of the phenomenon is considered in a staggered fashion using a single, indeformable Finite Element mesh. A fractional step and a monolithic strategy are used for the water flow and granular phase, respectively. In this way, the maximum accuracy with minimal computational times is reached. The method is completed by adding the interaction terms due to drag and pressure forces, together with a moving mesh strategy to reduce the size of the computational domain.

Abstract

Abstract