hui Li

A super-large landslide in Tibet in 2000: background, occurrence, disaster, and origin

On April 9, 2000, a super-large landslide (3 x 10(8) m(3)) occurred along Zhamu Creek, southeast Tibet. As a result, a landslide dam formed and the Yigong River was blocked. A channelized diversion was constructed for prevention of overtopping. Two months later on June 10, a catastrophic flood resulting from the failure of the landslide dam caused a serious loss of property. This is the second of landslide occasion dam formation and flooding occurrence at the same site since 1900.

Design, construction and mechanical behavior of relics of complete large Longyou rock caverns carved in argillaceous siltstone ground

Abstract This paper presents a comprehensive summary of data, analyses and findings from the investigations over the past twelve years about the relics of large Longyou rock caverns carved about 2 000 years ago at shallow depths in argillaceous siltstone. The paper presents the typical features associated with the rock caverns. They include structures, large spans, portals, extreme shallow-buried depths, imprints, drainages, inclined ceiling, inclined sidewalls, slender rock pillars, rock staircases, site and strata selections, caving lighting, carving method, and underground construction surveying. They are used to reconstruct and highlight the design and construction methods adopted by the ancients. The paper further demonstrates that the relics of the complete large rock caverns are a consequence of coincidental combinations of ancient human effort and natural factors. The full occupation of water with weak acidity in the large rock caverns with the soft surrounding rocks of weak alkalinity is found to be the main factor ensuring and preserving the caverns to have been stable and integral over 2 000 years. However, the five unwatered complete rock cavern relics have been experiencing various deteriorations and small failures including cracks, seepage, small rock falls and delaminating ceiling rocks. Although these deteriorations have been repaired and stabilized effectively, the paper demonstrates that an entire roof collapse failure is highly possible in the near future to each of the five unwatered rock cavern relics. The findings presented in this paper are also invaluable both to the long-term protection and preservation of the large rock cavern relics of national and international interests and importance, and to extend and enrich our experience and knowledge on the long-term stability and integrity of man-made underground rock cavern engineering projects.

Validation of Spatial Prediction Models for Landslide Susceptibility Mapping by Considering Structural Similarity

In this paper, we propose a methodology for validating landslide susceptibility results in the Pinggu district (Beijing, China). A landslide inventory including 169 landslides was prepared, and eight factors correlated to landslides (lithology, tectonic faults, topographic elevation, slope gradient, aspect, slope curvature, land use, and road network) were processed, integrating two techniques, namely the frequency ratio (FR) and the certainty factor (CF), in a geographic information system (GIS) environment. The area under the curve (success rate curve and prediction curve) analysis was used to evaluate model compatibility and predictability. Validation results indicated that the values of the area under the curve for the FR model and the CF model were 0.769 and 0.768, respectively. Considering spatial correlation, an alternative complementary method for validating landslide susceptibility maps was introduced. The spatially approximate maps could be discriminated from their matrices which carry structural information, and the structural similarity index (SSI) was then proposed to quantify the similarity. As a specific example, the SSI value of the FR (74.15%) scored higher than that of the CF model (69.36%), demonstrating its promise in validating different landslide susceptibility maps. These results show that the FR model outperforms the CF model in producing a landslide susceptibility map in the study area.

The Cultural Relics Distribution Characteristics Along the Canal Line and Appraisal of its Influence by the Middle Route Project for Water Transferring from South to North China

Assessments of the impacts of environmental hazards on ecological systems and human health have become a subject of ever-increasing importance. In this work, we extend current ecological hazard evaluation to the problem of protecting cultural relics from hazards attributable to the presence of a large-scale canal system being planned in China. The development and utilization of water resources must be closely combined with the preservation of cultural relics. The Middle Route Project for Water Transfer from South to North China (MRWT) is a current example. In this paper, the engineering background of this project is briefly introduced. The distribution of cultural relics related to it is also summarized in terms of different geographical divisions. An influence index E = f(L, δh, k, I, v, s) is introduced to measure the comprehensive effect of the canal on cultural relics. Because this function is really established at the preconstruction stage, it is treated by use of fuzzy mathematics. Each cultural relic has its own E value. Cultural relics with E values greater than 0.75 should be paid high attention, while those with E less than 0.5 may generally be ignored. What must be preserved through use of engineering measures are cultural relics with E values greater than 0.9. As to those cultural relics with E ranging between 0.5 and 0.75, whether they should be preserved with engineering controls depends upon practical circumstances specific to each relic.

Comparison of rockfall susceptibility assessment at local and regional scale: a case study in the north of Beijing (China)

This study shows a rockfall susceptibility assessment at local scale in north Beijing of China, including the identification of rockfall sources onsite by terrain and rock discontinuities analysis and run-out distance prediction by Rocfall™ simulation. Two types of rockfall were defined including one type on the cliffs with long inclined slopes and another type on the road slopes with low height. Two historical rockfall events were used to back-calibrating the parameters used for run-out distance simulation. Based on the work, rockfall susceptibility map at local scale was created in GIS, which was compared with the map obtained at regional scale (entire Huairou district scale). Due to the difference of approaches applied, procedure of assessment and types of source data acquired, the two resulting rockfall susceptibility maps are proved to be different. Still, both of them are useful and could be used at different level’s decision for rockfall prevention and mitigation. Different types of uncertainties exist in the study of rockfall susceptibility assessment. To reduce the uncertainties, studies on both approaches and techniques are suggested.

Geometric Heterogeneity of Continental Shale in the Yanchang Formation, Southern Ordos Basin, China

Favorable prospects for the exploration of shale gas have been demonstrated in the Ordos Basin, China. Outcrop and core observations indicate that there are abundant laminas in the shale strata, which exert a great influence on hydro-fracture propagation, gas storage and fluid flow. In this study, the continental shale of the Chang 72 Member, collected from the south of Ordos Basin, was investigated to characterize the geometric heterogeneity. Laminas at multiple scales were observed and measured using conventional logging, borehole TV, core analysis, scanning electron microscopy, and the Particle and Crack Analysis System. These measurement tools correspond to the meter scale, decimeter scale, centimeter scale, millimeter scale and ten-micrometer scale, respectively, with measured thicknesses of 2.26 m, 2.09 dm, 1.70 cm, 1.48 mm and 11.70 μm, respectively. Fractal theory was used to analyze the power exponent distribution of the lamina thickness, with a resulting fractal dimension of 1.06. Finally, a geometric heterogeneity model was proposed for the Upper Triassic Yanchang Formation in the study area and verified by a modeled thickness of 26.30 m for the Chang 72 Member at the 10-m scale. The model facilitates cross-scale analysis and provides parameter guidance for heterogeneity characterization in the numerical simulation and model test of the shale gas reservoir.

Stability of Large-Scale Rock Cavern Complex at the 800-Year Feifengyan Quarry

This paper deals with long-term stability of an ancient large underground rock cavern complex excavated some 800 years ago in Zhejiang Province, SE China. The rock cavern complex is characterized by complicated geometric aligns, unique structure designs, large spans with shallow depths. Its rock mass characteristics were firstly investigated and the favorable rock mass quality was verified using the collected in-situ data. Distinctive quarrying method-Digging Holes for Quarrying Vertical Flagstone (DQF) was introduced the ancients to ensure safe excavation, it proved much smarter than modern blast-casting method. The favorable rock mass quality, smart structure designs, and ingenious quarrying technique were concluded to collectively lead to the noticeable long-term stability of the cavern complex. These ancient achievements mark high level of quarrying in complicated geo-environments with manpower, the results are positive to extend our knowledge in category design of cavern scale and stability assessments.

Siting method of the ancients in the excavation of Longyou Caverns, 2000 years ago

Abstract In June 1992, five large rock caverns were unearthed in a village near Longyou County in Zhejiang Province, south China. The caverns were manually excavated about 2000 years ago in argillaceous siltstone of Cretaceous age. Faults are not well developed, however there are clay interlayers within argillaceous siltstone bedding at each cavern. Field investigations suggest that the ancients had realized the influence of the clay interlayers on the stability of caverns and altered their location and layout accordingly. Several preserved trial adits at the site are good evidence of this conclusion. These adits are apparently abandoned due to the presence of clay interlayers. This is probably the earliest known use of geological exploration by adit methods, an approach now widely used. In this paper, the engineering geological conditions, especially the development of the clay interlayers, are presented in some detail. Statistical analysis shows that the numbers and average thickness of clay interlayers in the five completed caverns are less than those in other outcrops. It is concluded that trial adit methods and experience by geological observation were adopted by the ancients 2000 years ago in the excavation of underground rock caverns.

Slope Geometry Design, Deformations and Failures of Ancient Quarries in Zhejiang Province, China

There are many ancient quarry slope sites in Zhejiang Province, China. The typical quarries are Shanghuashan in Ningbo, Donghu, Houshan and Keyan in Shaoxing, Dafo Temple in Xinchang and so on. These slopes were excavated by the ancients 700 years even more than 2,000 years ago. Nowadays, these sites are all opened to the public for tourism. According to the field engineering geological investigations, the maximum height of the slopes is 60 m. Unique slope geometry design was made by the ancients to get larger production of stone and obtain safety of the workers: arc countertendency slope, arc slope in horizontal plane, supporting thin wall in the orthogonal direction to slope, triangular blocks supporting the top of the slope in a countertendency, horizontal bench along slope below fault etc. These geometries designed by the ancients can be reference for the modern quarry. Nowadays, deformations and failures occurred in some of the slopes: wedge failure, pressure shear or tensile crack, slide along the bedding plane or fault. Thoroughly engineering geology studies should be carried out as soon as possible to ensure the safety of the tourists and protect the ancient sites of quarry.