Study on Deformation Evolution Characteristics of Reverse-Dip Rock Slope under the Influence of Rainfall

In Southwestern China, there exists deep river valleys and abundant rainfall, which leads to a large number of reverse-dip rock slopes. In order to investigate the evolution characteristics of toppling deformation of reverse-dip slope under the influence of rainfall, and a typical reverse-dip slope was taken as an engineering case. Firstly, the temporal and spatial evolution nephogram of toppling displacement under different rainfall was obtained based on the discrete surface displacement monitoring data of bank slope. Then, taking bank slope, gully buffer zone, and development degree of bank slope as development characteristics based on geological field survey, afterward, the evolution characteristics in different strong deformation zones were analyzed by superimposing the development characteristic partition and the spatial and temporal displacement nephogram. The results showed that the horizontal displacement mainly occurred on the right front and middle rear of the bank slope while large vertical displacement occurred on the middle of the bank slope under the influence of rainfall. As the rainfall increased to the maximum, the toppling deformation reached the peak, and vertical displacement was more sensitive to the rainfall than horizontal displacement. After the superposition, the largest strong deformation zone was located in the middle and rear part of the bank slope, which is characterized by medium and high slope and mature stage and 50 m gully buffer zone. This paper explores the deformation and failure process of reverse-dip rock slope considering the change of rainfall through real displacement monitoring data and focuses on the real deformation evolution law of each characteristic zone combined with different development characteristics partition.

Emergency Survey and Stability Analysis of a Rainfall-Induced Soil-Rock Mixture Landslide at Chongqing City, China

The stability analysis of damaged landslides and unstable debris is important for rescue work and emergency operations. This paper investigates a predisposed geological emergence, inducing the factors and deformation processes of the Zhongbao landslide, which happened on July 25, 2020. The stability of the landslide debris was evaluated by an integrated monitoring system consisting of ground-based radar, unmanned aerial vehicles, airborne Lidar, thermal infrared temperature monitoring, GNSS displacement monitoring, deep displacement monitoring, and rainfall monitoring. The strata and weak layer controlled the landslide failure, and topography defined the boundary of the failed rock mass. A continually intensive rainfall caused the deformation and accelerated failure of the landslide. The shallow and steep deposit (Part I) firstly slid at a high velocity, and then pushed the rear part of the landslide (Part II) to deform, forming numerous cracks, which accelerated the rainfall infiltrating into the rock mass. The moisture content increase could decrease the strength of the shale rock within the bedding planes. Finally, with the rock and soil mass sliding along the weak layer, a barrier dam and a barrier lake were formed. The monitoring and numerical simulation results showed that after the landslide failure, there was still local collapse and deformation occurrences which threatened rescue work and barrier lake excavation, and the stability of the accumulation area gradually decreased as the rainfall increased. Therefore, the barrier dam was not excavated until the accumulation rate gradually stabilized on July 28. Moreover, most of the reactivated deposits still accumulated in the transportation and source areas. Thus, in August, the displacement of the landslide debris gradually accelerated in a stepwise manner, and responded strongly to rainfall, especially in the accumulation area, so that it was inferred that the damaged landslide could slide again and cause a more threatening and severe failure. The analysis results of the study area can provide references for the failure mechanism of a rainfall-induced landslide and the stability evaluation of a damaged landslide.

Crack-Considered Elastic Net Monitoring Model of Concrete Dam Displacement

Displacement monitoring data modeling is important for evaluating the performance and health conditions of concrete dams. Conventional displacement monitoring models of concrete dams decompose the total displacement into the water pressure component, temperature component, and time-dependent component. And the crack-induced displacement is generally incorporated into the time-dependent component, thus weakening the interpretability of the model. In the practical engineering modeling, some significant explaining variables are selected while the others are eliminated by applying commonly used regression methods which occasionally show instability. This paper proposes a crack-considered elastic net monitoring model of concrete dam displacement to improve the interpretability and stability. In this model, the mathematical expression of the crack-induced displacement component is derived through the analysis of large surface crack’s effect on the concrete dam displacement to improve the interpretability of the model. Moreover, the elastic net method with better stability is used to solve the crack-considered displacement monitoring model. Sequentially, the proposed model is applied to analyze the radial displacement of a gravity arch dam. The results demonstrate that the proposed model contributes to more reasonable explaining variables’ selection and better coefficients’ estimation and also indicate better interpretability and higher predictive precision.

Precise Cement Displacement with a New Cement Plug Tracking Method

During the primary well cementing operation, when the cement slurry is pumped into the annulus around the outside of the casing string, it is very critical not to over displace and let the displacement fluid enter the annulus. Traditionally, to determine when to stop the cement displacement operation, the top cement plug position is tracked volumetrically by dividing the displaced volume by the casing internal cross-sectional area. However, the volumetric method is prone to uncertainties related to displacement fluid compressibility, high-pressure pump inefficiency, flowmeter inaccuracy, and variance in casing joint diameters. The new cost-effective cement displacement monitoring method is based on the analysis of the pressure pulses generated by the top cement plug passing the casing. These pressure pulses are detected by the standard pressure transducer installed at the cementing head. When correlated with the casing tally, these pulses identify the plug position related to the completion elements that provide better accuracy than the volumetric method used conventionally. The case studies include the successful cement displacement monitoring example and the case where the plug was prematurely stopped 90 meters above the landing collar, which was revealed by the subsequent drilling and confirmed independently by the new plug tracking method.

Forced displacement: an emerging indirect impact of Covid-19 pandemic in America and the rest of the world. Prospects and Solutions

Background and aimsDespite Global efforts in the ongoing COVID-19 pandemic response, the SARS-Cov-2 virus presents a growing concern for the forced displacement of persons from their communities. People are forcibly evicted or displaced to other places by both the direct or indirect sequelae of the disease. The direct sequelae have been the movement of people from communities of high COVID-19 endemicity to areas of a perceived low COVID-19 endemicity and, or threats to life. The indirect sequelae have occurred mainly following the associated shutdown of social services (hospitals, schools, transportation, etc.), eviction from community or housing, and loss of livelihood posed by COVID-19. New policy and practice approach in the Global pandemic response that incorporates timely measures to address any COVID-19 induced forced displacement and offer humanitarian assistance to individuals impacted are needed. This is also on the hill of a looming lifting and or expiration of the Centers for Disease Control and Prevention “temporary protection of housing eviction (eviction moratorium)” in the USA and elsewhere, so many individuals or families will likely be homeless and become internally displaced persons post public health emergency declaration. The present study aims to bring to the limelight this ongoing but yet to addressed complications of the COVID-19 pandemic and recommends possible solutions for this pandemic and any future disease outbreaks. MethodsWe carried out multiple online and database searched on COVID-19 induced-forced displacement of persons. Furthermore, we conducted an online search of COVID-19 induced displacement monitoring and tracking in the USA and globally, as well as that on data collected and/or compile through intergovernmental organizations (IGOs) and non-governmental organizations. In a narrative review, we try to identify COVID-19 induced forced displacement data provided online from the inception of the pandemic outbreak-December 2019 to August 2021. ResultsWe included data from a biannual data report on forced displacement provided by three intergovernmental organizations as identified on their websites. Recommendations were made for incorporating active monitoring and tracking of COVID-19 induced Force displacement/evicted persons post expiration of “temporary protection from housing eviction” in the Global pandemic effort with a view to providing baseline data for intervention and targeted humanitarian assistance to displaced persons.ConclusionsThe COVID-19 pandemic continues to cause forced displacement of persons and communities, alongside attendant humanitarian needs. Incorporating COVID-19 induced forced displacement monitoring and tracking is a key solution to minimizing the collateral suffering, morbidity, and mortality associated with the ongoing COVID-19 pandemic or future disease outbreak. We also suggested the establishment of a specific center for Disease outbreak (COVID-19 pandemic) induced-forced displacement studies in America.