Recent developments of generalized plasticity models for saturated and unsaturated soils

Soil undergoes both elastic and plastic deformations under different loading conditions. A relatively accurate constitutive model of soil behaviors should be capable of predicting the elastic and plastic deformations properly. Among a large number of elastoplastic constitutive models developed over the last several decades, constitutive models based on generalized plasticity have been successfully utilized in modeling the mechanical behavior of various soils. This paper attempts to present a review of the most recent developments of generalized plasticity models for geotechnical problems. After a brief review of generalized plasticity theories and constitutive models, limitations of the original Pastor-Zienkiewicz model in practical application are summarized. Afterwards, recent achievements in the generalized plasticity models for both saturated and unsaturated soils and their applicability are analyzed, and a general approach for modification of generalized plasticity models is highlighted.

Research progresses on equipment technologies used in safety inspection,repair,and reinforcement for deepwater dams

China’s many dams are increasingly facing safety problems resulting from the natural aging of the dam hydraulic structure and geological disasters such as earthquakes under the operating condition of holding a vast amount of water.Problems such as dam leakage and concrete cracking and erosion seriously affect the normal operation and effectiveness of a reservior.It is impossible to empty a large reservoir with a high dam for many reasons,such as serious environmental consequences,and it is thus difficult to detect the working conditions of the underwater part of the facility.There is an increasingly urgent demand for detection and repair technologies that can be used in the deepwater environment.Indeed,there are cutting-edge deepwater detection and processing technologies for hidden dangers in dam engineering.The core technologies include underwater detection equipment,diving technologies,and underwater operation technologies.This paper analyzes safety-oriented detection equipment recently used in unmanned detection,manned detection,and deepwater diver detection from the viewpoint of practical application.The paper further reviews 100-m-depth-class technologies and applications of safety inspection,repair,and reinforcement equiment in the deepwater environment of reservoir dams.An outlook is provided on technology trends of deepwater detection,repair,and reinforcement and critical problems.

Resilience of hydraulic structures under significant impact of typhoons

Vulnerability to natural disasters falls into three categories： exposure, resistance, and resilience, where resilience mainly refers to the capability of a pressure-bearing system to recover by returning to its initial state, that is, the ability to adapt to disaster pressure. Resilience is a major subject of research on disaster prevention and mitigation. This research mainly focuses on the ability of the hydraulic structure to recover from the significant impacts of typhoons. According to the load/unload response ratio theory, the degree of instability by which nonlinear systems can be identified according to the difference between load and unload responses was analyzed. This analysis was used as a basis to study the resilience of a hydraulic structure. Taking the Yangtze River embankments under the impact of Typhoon Matsa as an example, the ability of the typical sections of different types of embankments to adapt to the significant impact of the typhoon, i.e., the resilience of the hydraulic structure, is described with the help of the load/unload response ratio （L）. The results of the calculated resilience reflect the actual conditions of the structure and can be used to determine the applicability of the embankment section. The load/unload response ratio theory is one of the effective tools for calculating the resilience of hydraulic structures under the significant impacts of typhoons.