Search

As flexible resources, cascaded hydropower stations can regulate the fluctuations caused by wind and photovoltaic power. Constructing pumped-storage units between two upstream and downstream reservoirs is an effective method to further expand the capacity of flexible resources. This method transforms cascaded hydropower stations into a cascaded pumped-hydro-energy storage system. In this paper, a flexibility reformation planning model of cascaded hydropower stations retrofitted with pumped-storage units under a hybrid system composed of thermal, wind, and photovoltaic power is established with the aim of investigating the optimal capacity of pumped-storage units. First, a generative adversarial network and a density peak clustering algorithm are utilized to generate typical scenarios to deal with the seasonal fluctuation of renewable energy generation, natural water inflow, and loads. Then, a full-scenario optimization method is proposed to optimize the operation costs of multiple scenarios considering the variable-speed operation characteristics of pumped storage and to obtain a scheme with better comprehensive economy. Meanwhile, the proposed model is retransformed into a mixed-integer linear programming problem to simplify the solution. Case studies in Sichuan province are used to demonstrate the effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

At 12:52 pm on September 5, 2022, an Ms 6.8 earthquake occurred in Luding County, Sichuan Province, China. Based on high-resolution aerial photographs and satellite imageries obtained after the earthquake, as well as field investigation, a total of 8685 earthquake-triggered landslides (EQTLs) were interpreted. The landslides covered an area of 30.7 km2, with a source area of 9.4 km2. These EQTLs were mainly distributed in areas with a seismic intensity of VIII and IX. Most of the landslides were small and medium in size, and their types included landslide, rockfall, and rock slump. Characteristic landslide distributions were found, EQTLs were distributed along the Xianshuihe fault, landslide area decreased gradually with an increased distance to the fault; EQTLs were distributed along the Daduhe River and roads; besides, landslide distribution was associated with ground deformation caused by the earthquake. EQTLs' characteristics indicated that, a large number of EQTLs were located near the foot of the slope; the full area of EQTLs and their source area followed a power function. This study concluded that Luding EQTLs were greater in number and area but relatively smaller in terms of affected area. Investigations on geo-hazards post-earthquake and risk assessment were proposed in the earthquake-stricken area to support the rehabilitation and reconstruction. [ABSTRACT FROM AUTHOR]

On 05 September 2022, an Ms 6.8 (Mw 6.6) earthquake occurred in Luding County, Sichuan Province, China, with the epicenter at 29.59°N, 102.08°E and a focal depth of approximately 16.0 km. Combining field investigations, high-resolution satellite images and multiple datatpes characterizing the seismogenic structure, topography and geology, this study attempts to discuss the influence of geomorphic and tectonic indexes on landslide distribution. The results show that the 2022 Luding earthquake with seismogenic fault at the Moxi fault, was a sinistral strike-slip event that triggered at least 4528 landslides over an area of ∼2000 km2. These landslides span a total area of 28.1 km2, and the western section of the seismogenic fault, which serves as the active wall area, is characterized by a higher landslide concentration, especially in the Wandong Basin. The seismogenic fault and lithology influence the regional distribution of landslides, and more landslides occurred closer to the seismogenic fault and in the controlling lithologies of granite and dolomite. Local topography influences the landslide occurrence position on the slope; the eastern section is prone to form landslides in the lower gorge section, and the western section is prone to form landslides in the upper-top section of the gorge. For coseismic landslides in the eastern Baryan Har block, the eastern boundary (Longmenshan fault), where the earthquakes are characterized by thrusts with slight dextral strike-slip movement, could be the primary landslide-prone area; the southern boundary, the Moxi fault and the southern segment of the Xianshuihe fault, with more intensive strike-slip movement, may be the secondary landside-prone area; and the northern boundary is the tertiary landside-prone area. Additionally, the current landslide inventory may be underestimated although this underestimation has limited influence on the results. [ABSTRACT FROM AUTHOR]

On 5th September 2022, a magnitude Ms-6.8 earthquake occurred nearby Mt. Gongga, western Sichuan. The stability of the glaciers in east Mt. Gongga close to the epicenter was widely concerned due to the strong shake triggered by the earthquake. Using multi-source observations (including in-situ photographs, remote sensing datasets before and after the event), we carried out a preliminary assessment of the stability and hazard risks of the Hailuogou (HLG) glacier. Triggered by the earthquake, a small block of fractured ice at the lowest part of icefall collapsed. The magnitude of the coseismic ice avalanche was relatively small, which is comparable in size to most ice avalanches over the past seven years, but much less than the previous mapped largest one (03 April 2018, runout ∼699 m). One most recent large (runout ∼608 m) ice avalanche occurred between 01 and 04 September, just before the earthquake, likely unloaded large amount of ice mass and made a larger ice avalanche avoided during the earthquake shake. Nevertheless, the momentum of collapsed snow-ice-rock mass could be safely unloaded over a wide and gentler-slope ice tongue area, limiting its mobility and the risk of a cascading hazard. Glacier-wide surface flow dynamics monitored by Sentinel-1 satellite SAR time series (12 September 2021–19 September 2022) show that HLG glacier velocity was generally consistent before and after the earthquake. The entire HLG glacier exhibited more stable than expected, with almost no abnormal features detected in its upper accumulation part, the lower ice tongue, and its lateral paraglacial slopes. Since the glacier valley has experienced remarkable downwasting and the paraglacial environment has been strongly disturbed and destabilized, we suggested that, to efficiently evaluate glacier-related cascading hazard risks, it is also necessary to systematically combine multi-source observations (e.g., high-resolution UAV survey, radar/Lidar scan, ground investigation, monitoring and warning systems) to continuously monitor the regional glacier anomalies in the post-earthquake seismic active areas. [ABSTRACT FROM AUTHOR]

With the rapid urbanization, an increasing number of landslides have been induced by human activities. In this study, a typical human-induced landslide known as the Maobazi landslide, which was triggered by foundation pit excavation in Sichuan Province, China, was analyzed. An emergency investigation was carried out to detect the basic deformation characteristics, followed by implementations of multiple monitoring schemes and emergency control measures to monitor and control reactivated deposits. The reactivated deposits depicted rapid deformations with a maximum deformation exceeding 140 mm from July to September before the emergency control measures were completed. The reactivated deposits gradually settled and were finally controlled in 2019. The results showed that the 2019 Maobazi landslide was a large; reactivated landslide with a scale reached to 520 Mm3, which could result in catastrophic consequences if it slipped down to nearby residential areas. [ABSTRACT FROM AUTHOR]

On June 17, 2020, an unexpected rainstorm struck the Meilong valley, which is located in Danba County, Sichuan Province, China. The cumulative rainfall of this short-duration event reached 38.1–42.4 mm and triggered the Meilong debris flow. The Meilong debris flow rushed into the valley and forced the Xiaojinchuan (XJC) River to flow along the foot of the ancient Aniangzhai (ANZ) landslide. Intense erosion reactivated the ancient ANZ landslide, producing a reactivated area of 0.62 km2. Subsequently, emergency investigation and monitoring were conducted to monitor its deformation because unstable landslide conditions could pose a serious threat to the safety of lives and property downstream. Emergency monitoring over 20 days (June 23, 2020–July 12, 2020) indicated that the reactivated deposit decelerated and entered the constant deformation state; careful attention should be paid to this reactivated deposit. [ABSTRACT FROM AUTHOR]

At approximately 2:00 p.m. (Beijing time) on August 6, 2019, the previously controlled Leidashi landslide was reactivated near group 7 of Zhangjiagou village, Jianyang County, Sichuan Province, China. The 2019 Leidashi landslide damaged two main roads and 44 antisliding piles and posed a threat to another main road. This landslide was a reactivation of the 2010 Leidashi landslide and had an accumulation zone of 2.2 × 106 m3. To explore the deformation characteristics and failure mechanism, detailed field investigations, unmanned aerial vehicle photogrammetry, airborne LiDAR surveys, borehole drilling and inclinometer installation were carried out, and the collected data were analyzed. The results show that the 2019 Leidashi landslide could be divided into main slipping zone and activated zone according to movement state, and the main slipping zone could also be divided into main scarp area, main deposit area, climbing area, uplift area, and local landslide area according to the local movement and geomorphic features. The rapidly increasing landslide thrust caused by short-term but continuous heavy rain caused the failure of the antisliding piles and ultimately reactivated the 2010 landslide. [ABSTRACT FROM AUTHOR]

On April 20, 2013, the Lushan M7.0 earthquake struck at the southern part of the Longmenshan fault in the eastern Tibetan Plateau, China. The shear-wave splitting in the crust indicates a connection between the direction of the principal crustal compressive stress and the fault orientation in the Longmenshan fault zone. Our relocation analysis of the aftershocks of the Lushan earthquake shows a gap between the location of the rupture zone of the Lushan M7.0 earthquake and that of the rupture zone of the Wenchuan M8.0 earthquake. We believe that stress levels in the crust at the rupture gap and its vicinity should be monitored in the immediate future. We suggest using controlled source borehole measurements for this purpose. [ABSTRACT FROM AUTHOR]

Seismic site effects (local topographic/lithologic amplification, directivity phenomena) can have substantial impact on slope dynamic response and susceptibility to earthquake-induced failures. However, the instrumental data needed to quantify the site effects on slopes are still scarce. Here we investigate dynamic response of steep slopes in the Dadu River valley (Sichuan Province), one of the China's regions most struck by large magnitude earthquakes. We analyse ambient noise recordings acquired at the sites of a local accelerometer network established few years after the 2008 Wenchuan earthquake. The analysis benefits from the application of a new technique that determines the ellipticity of Rayleigh waves present in noise wavefield from the instantaneous polarization analysis of the recorded signals. The technique is adapted for application to steep surface by rotating the noise recordings according to a reference having as axes the slope down-dip direction, the slope surface strike and the normal to the slope surface. This allows obtaining the curve of Rayleigh wave ellipticity as function of frequency, whose maxima provide information on site response characteristics, and leads to a more reliable identification of resonance phenomena on steep slopes (40° inclination). The results of the ambient noise analysis are consistent with the available accelerometer data and provide clear indication of significant resonance effects, with regard to their potential impact on local seismic slope stability. In particular, the slopes around the confluence of a local torrent with the Dadu River near the Lengzhuguan village exhibit strong site amplifications related to the presence of surficial deposits overlying intensely fractured granite bedrock. The frequency, amplitude and direction of resonance phenomena derived from the analysis of instrumental data indicate that site amplification is likely to have lesser impact on the stability of the lower part of the Mt. Dagang, which forms a long steep sub-planar slope facing the Dadu River. Our findings demonstrate that expeditious ambient noise recordings can provide useful information on relative susceptibility of slopes to seismically induced failures. • Slope dynamic response characterization integrating ambient noise and seismic data • Improved results of noise analysis on steep slopes by suitably rotating recordings • Noise recording repetitions needed to reliably infer site response properties. • Site response short-distance variations due to variably thick surficial deposits. • Rock fractures, slide deposits and topography influence susceptibility to failure. [ABSTRACT FROM AUTHOR]

The authors have retracted this article [1] because they did not have permission to publish most of the figures and data in this article. [ABSTRACT FROM AUTHOR]