This announcement is a first attempt to systematically describing the participants, roles, activities, and complex interactions involved in different stages of the dam life cycle ( ICOLD, 2021) and to capture all related dam safety aspects in all preoperation stages. Many risks of dam operation come from other steps before the actual operation. 175 extends the traditional method and concept to all stages before the operation stage. International Commission on Large Dams (ICOLD) Bulletin No. It is of great significance to learn lessons from the past dam break events and discuss the main rules of dam break for revealing the dam break mechanism of the reservoir and improving the safety management level of the reservoir. Due to the compatibility of loess, the mechanical properties in a saturated state, and the relatively uniform gradation, there are various unpredictable dam break factors in the design, and construction of reservoir dam failure risk is still an important problem in dam design, construction, and operation. Because of the depth and breadth of loess distribution, local materials are usually needed in the design and construction process of the dam foundation and dam body. The main functions of reservoirs in Ningxia are irrigation, water supply, and aquaculture. About 280 reservoirs with a total storage capacity of 1.736 × 10 8 m 3 have been built in the Loess region of Ningxia. This study gives some design suggestions for using this loess for dam building, for example, through the design of the filter layer to increase the difficulty of piping occurrence.īy the end of 2021, China has built about 100,000 reservoirs of all types, with a total storage capacity of about 9.0 × 10 11 m 3 ( Ministry of Water Resources of the PRC, 2021). The research results show that using this loess to fill the dam foundation directly and the dam body has a very high probability of piping-type dam failure. Finally, the undrained characteristics of saturated loess are tested, and the dam failure is essentially explained.

Second, the particle size distribution confirmed the mechanism of uneven particle size distribution and clay loss. We mainly carried out the research through the following three aspects: First, the dam structure was identified by using the seismograph, the compactness of the dam foundation and the dam body was determined according to the wave velocity of the soil layer, and the construction quality of the dam foundation and the dam body was comprehensively evaluated. This study tries to find out the real reason for dam break from the physical and mechanical properties of the foundation and the dam. The dam break is a gradual development from piping to complete dam break.

The study investigated the 2021 dam failure of the Yang village reservoir in Ningxia, China, which resulted in millions of dollars of property damage but no casualties. Therefore, it is of great significance to study the mechanical characteristics of loess in the saturated state for preventing dam break. Near-static liquefaction of the loess in the dam body under the saturated condition will lead to piping or loss of soil strength. Piping channels easily form under the action of force and collapsibility.

The main reason may be that although the gradation of loess particle is not uniform. The construction of a reservoir on a large-thickness collapsible loess cover will significantly increase the occurrence of dam break disasters.

3Key Laboratory of Loess Earthquake Engineering, China Earthquake Administration and Gansu Province, Lanzhou, China.

2Institute of Solid Mechanics, Ningxia University, Yinchuan, China.

1School of Physics and Electronic-Electrical Engineering, Ningxia University, Yinchuan, China.

Wenguo Ma 1,2, Gang Zhang 2*, Youzhen Yang 1,2, Ping Wang 3, Yishen Zhao 1,2 and Qingqing Lin 1,2

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