Yang Wentao,Wang Yunqi,Sun Shao,Wang Yujie,Ma Chao
Detecting slope movement before landslides occur in mountain regions is crucial for disaster reduction. In October 2018, a gigantic landslide occurred on the Jinsha River, causing dammed-lake breach flood 500 km downstream. In this work, we used 25 Sentinel-2 images from November 2015 to August 2018 to explore the capability of this high temporal resolution optical images in detecting slope movement before the Jinsha River landslide. Normalized difference vegetation index (NDVI) was calculated to composite temporal profiles using all Sentinel-2 images. With this NDVI time series, unsupervised K-means classifier was applied to initially classify the study area and find the best thresholds for automatically extracting landslide scars in the image series. These extracted landslide scars were validated using interpreted results from two high spatial resolution images of similar dates in 2015 (user’s accuracy 89.7%, producer’s accuracy 83.6%) and 2018 (user’s accuracy 90.8%, producer’s accuracy 74.9%). After validation, extracted landslide scars of different years were counted and displayed in an RGB composite image to highlight slope movement. In addition, monotonous decrease/increase of NDVI was also observed, indicating continuous expansion of landslide scarps and movement of landslide head along the slope on the landslide surface. This work demonstrated the capability of Sentinel-2 time series images to capture slope movement with short revisit time at low cost. By incorporating other environmental information (such as elevation), this proposed method has the potential to consistently map pre-landslide slope movements over a large region.
Aoyang Sha,Huifang Yang,Zhengyan He,Qin Zuo,Zhigao Xu,Chenjie Wu,Ming Wu,Ru'an Chi
In-situ leaching process of weathered crust elution-deposited rare earth ore (WCE-DREO) often faces problems such as poor permeability and occurrence of landslides. The main reasons are the swelling of clay minerals by water absorption and blockage of seepage channels by fine particles. This study proposed using hydroxypropyl methyl cellulose (HPMC) as a novel green swelling inhibitor with the combination of ammonium sulfate ((NH 4 ) 2 SO 4 ) as an efficient composite leaching agent. The swelling inhibition performance of HPMC on swelling inhibition was evaluated through linear swelling tests and mud ball immersion tests. The mechanisms of HPMC on swelling inhibition and seepage promotion were analyzed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Scanning electron microscopy (SEM), Surface area analysis (BET), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), and the contact angle, zeta potential and particle size distribution were characterized. The results indicated that HPMC showed a good performance on swelling inhibition, which improved with the increase of HPMC concentration. HPMC expels the water from the interlayer. Moreover, HPMC adsorbs onto the surface of clay minerals by hydrogen bonding to form a hydrophobic film, which can prevent the clay minerals from hydration swelling. Due to the electric neutrality property of HPMC, the electrostatic repulsion of clay minerals can be reduced. Therefore, the fine particles of the clay minerals can be bridged to form larger particles by the long carbon chain of HPMC which leads to expansion of the seepage channels as well as the improvement of the permeability of the ores. According to the column leaching tests, the novel leaching agent composed of 0.05 wt% HPMC and 2 wt% (NH 4 ) 2 SO 4 not only showed a good leaching capacity of rare earth, but also inhibited the swelling of clay and enhanced the seepage when comparing with traditional leaching agent ((NH 4 ) 2 SO 4 ). Developing a novel leaching agent benefits the green, safe and high-efficiency exploitation of WCE-DREO.
危险品化学品经营许可证（带存储）