The vane shear rheometer was used to study the rheological properties of the water-bearing sand layer. The test curves including shear resistance,water content,pore water pressure and strain velocity were obtained. The results show that the rheological curves of the sand layer appear obvious different phases,stable rheological stage and accelerated rheological stage,with the water content increasing. The former stage experiences the elastic deformation, initial and non-accelerated rheological processes. When shear resistance achieves the yield resistance strength,the sand layer entered the accelerated rheological stage,and the strain velocity increases quickly. Based on the fitted curves of accelerated rheological stage,the relations between loading shear resistance,yield shear strength and stress velocity were obtained. The analysis indicate that the resistance strength of dry sand comes from the friction between particles,when the water content increases the particles are surrounded by the water which decreases the acting forces between the particles. Therefore,the rheological properties change obviously. The yield resistance strength is the critical parameter to reflect the change process which is connected with the loading shear stress and water content.

The primary question in the debris flow initiation study is differentiation of the initiation process from other processes. This paper introduced a new experimental method and apparatus which can apply artificial rain, detect deformation, resistance and other variables. Based on the experimental data analysis, the definition of debris flow initiation process was promoted and demonstrated. Debris flow initiation is defined as the period in which the strain acceleration of soil mass is greater than zero. The experiment mainly focused on four aspects during the debris flow initiation process: (i) the paper analyzed a series of variables detected by the experiment (strain, resistance, water content and pore-water pressure), (ii) initiation process was defined by the key variable of strain and its propagations, (iii) in order to facilitate further study, initiation process was distinguished into initiation and acceleration processes, (vi) the characteristics of debris flow initiation process was studied. Finally, the experiment results can be used to describe many phenomena such as the abrupt nature of debris flow disasters.

The mountain hazards like snow avalanches, landslides, rock falls, debris flows all have strong destructive power which seriously threaten human lives and belongings. Therefore, it is necessary to study more about the happenings and developments of these disasters. Among the important and common features of the debris flow, the entrainment is the one that can increase the volume of debris flow and affects significantly the flow motion. These influences usually result in a more harmful and stronger destructive power. With the method of finite volume discretization, the numerical simulation of the entrainment process of debris flow is achieved in this paper. The influences of entrainment capabilities on the motion and deposition of debris flow are mainly studied. The typical engineering examples show and prove the stability and effectivity of numerical methods. © 2011 Casa Editrice Università La Sapienza.

Jinping-1 hydropower station is a key underground hydroelectric power project in the southwest of China.The powerhouse of this project is very large and under complicated poor geological conditions with a maximum crust stress of 35MPa,which brought many difficulties and a great challenge to the design and construction and high uncertainties of the caverns safety.A back-analysis of the powerhouse construction process is quite necessary.In this paper,the layout,principle,structure and implementation of the back-analysis system is briefly described,and some new developments are demonstrated in details,such as the zonal modeling of crust stress field,the convergence-increment hybrid target function and variable loosening zonal model.Finally this paper shows how this system works out an optimum and adjusts the excavation and cavern supports,and the roles of back analysis in making prediction and warning to ensure the power house safety.

A brief introduction is given to the great challenge in the construction of Jinping I hydropower station,which is a key cascade underground hydropower projectl,ocated in the Southwest China,at the Yalong River.The challenge is caused by the following features.The project is very huge and the underground powerhouse system is very complicated,as well as the very high geostress and the complex geological conditions,including 3 large-scale faults and multiple sets of joints existing in the surrounding rock mass with poor quality combination.A detailed description is carried out to the extremely large deformations which is far beyond the deformation of other underground powerhouses with the same range of scale,and the time-related features of the deformation,the severe cracks of linings,the damaged zones develop continually,the over-loading of the rock-bolts and anchorages,during the excavation of the underground powerhouse caverns.All these phenomena happen frequently.Then,a preliminary analysis of those particular situations is given from the point of view of the relation of high stress level and the rheological feature of the rock mass.Finally,the feasibilities of several countermeasures are discussed,such as gradual support method,hierarchical controlling to the initial pre-stress of anchors,damage-zone consolidation and strengthening by the combination of bolting and grouting.

Ground Penetrating Radar(GPR) is a reliable,high-resolution and economical method for studying the soil erosion,especially the sediments.Application of ground penetrating radar technology in soil erosion are described systematically,including the basic theory,the measuring method,data processing technology,data explanation,etc.Furthermore,GPR survey was carried out to investigate the bottom profile and sediment at Baigongyan Reservoir.The result shows that GPR can be used to rapidly produce high quality sub-bottom profiles showing sediment location and thickness.

泥石流的黏粒含量对泥石流容重(γC)有很大的影响. 通过对我国西南地区45条典型的沟道泥石流容重与黏粒含量关系的统计分析, 基于黏粒含量, 使用多项式对泥石流容重进行计算, 取得良好的结果, 所建立的广义多项式模式和针对黏性泥石流的对数模式可应用于无法观测的泥石流沟的泥石流容重计算. 计算结果与实际观测分析的误差较小, 这说明该模式具有很强的针对性. 通过分析确定泥石流黏粒含量与容重的关系是黏粒含量影响泥石流的形成、运动和悬浮颗粒粒径的结果, 其机理清楚可靠. 通过泥石流黏粒含量与容重的关系趋势线分析发现黏粒含量很少(3%以下)时, 形成的泥石流通常为稀性泥石流, 泥石流体的容重随黏粒含量的减少而减小, 这种泥石流随着黏粒含量的降低向水石流或者夹沙水流的状态发展. 黏粒含量在3%～18%之间时, 容易形成黏性泥石流, 黏粒含量在5%～10%时泥石流的容重随黏粒含量的增加而增加, 黏粒含量在10%～18%时泥石流的容重随黏粒含量的增加而减小. 黏粒含量超过18%时, 容易形成泥流, 这时候形成的泥流的容重与低黏粒含量时形成的稀性泥石流随黏粒含量的变化趋势相反, 性质方面也有很大差别, 黏粒含量在7%～11%之间时候形成的泥石流的容重平均值最大. 特别地, 对于黏性泥石流, 模拟出的对数容重计算公式, 适用于黏粒含量3%～18%的泥石流体, 该方程容重计算值最大可达2.32 (t/m3). 这与目前泥石流容重的最大观测值相符.

2003年8月28日22点左右,在强暴雨作用下,四川省雅安市石棉县蟹螺乡集中村相邻的两个流域:集中沟和热水塘沟同时暴发泥石流,造成较大的人员伤亡,其中集中沟2人死亡和失踪,房屋毁坏3幢;热水堂沟5人死亡和失踪,损坏2幢临时工棚;主河--弯坝河(大渡河的2级支流),被集中沟泥石流堵断数分钟后又被冲开,使弯坝河沿岸道路水毁200多米.流量较大的集中沟泥石流堆积物区面积2 300 m2,泥石流排入主河和堆积在堆积扇上的固体物质总量约2.8×104 m3.