Numerous landslides occurred in hilly and mountainous areas during the 2004 Niigata-ken Chuetsu Earthquake. Social problems developed when many towns became isolated because landslides cut offtraffic and public servic...Numerous landslides occurred in hilly and mountainous areas during the 2004 Niigata-ken Chuetsu Earthquake. Social problems developed when many towns became isolated because landslides cut offtraffic and public service lifelines. The hilly areas are composed mainly alternate layer of soft sandstone and mudstone deposited in quaternary or tertiary period. This geomorphology formed by folding presents a prominent landslide area in this region. This area has been utilized as rice terraces or carp breeding ponds because of plenty of water in the ground all the time. In addition, there was rainfall of more than 100 mm caused by Typhoon No. 23 two days before the earthquake in Chuetsu area. Block samples were extracted from the failure sites. The samples obtained were mainly low-cemented sandy soils. Triaxial tests of the samples under saturated and unsaturated conditions were conducted to examine the soils＇ strength properties and estimate the indices for slope stability.展开更多
Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical...Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.展开更多
文摘Numerous landslides occurred in hilly and mountainous areas during the 2004 Niigata-ken Chuetsu Earthquake. Social problems developed when many towns became isolated because landslides cut offtraffic and public service lifelines. The hilly areas are composed mainly alternate layer of soft sandstone and mudstone deposited in quaternary or tertiary period. This geomorphology formed by folding presents a prominent landslide area in this region. This area has been utilized as rice terraces or carp breeding ponds because of plenty of water in the ground all the time. In addition, there was rainfall of more than 100 mm caused by Typhoon No. 23 two days before the earthquake in Chuetsu area. Block samples were extracted from the failure sites. The samples obtained were mainly low-cemented sandy soils. Triaxial tests of the samples under saturated and unsaturated conditions were conducted to examine the soils＇ strength properties and estimate the indices for slope stability.
基金financially supported by National Natural Science Foundation of China (Grant Nos. 41172283, 41372313)National Basic Research Program of China (2012CB026103)
文摘Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.
