Rupture and safety of perilous rock are dominated by control fissure behind perilous rock block. Based on model-Ⅰand model-Ⅱ stress strength factors of control fissure under acting of weight of perilous rock, water pressure in control fissure and earthquake forces, method to calculate critical linking length of control fissure is established. Take water pressure in control fissure as a variable periodic load, and abide by P-M criterion, when control fissure is filled with water, establish the method to calculate fatigue fracture life of control fissure in critical status by contributing value of stress strength factor stemming from water pressure of control fissure in Paris’s fatigue equation. Further, parameters C and m of sandstone with quartz and feldspar in the area of the Three Gorges Reservoir of China are obtained by fatigue fracture testing.

Hitherto，perilous rock is the weakest topic in disasters studies．Specially, damage of control fissure under loads is one key technique in study of develop mechanism of perilous rock．Damage division of end area of control fissure was defined by authors，then calculation methods of timed-Poisson’s ratio and timed-Young’s modulus were established in damage mechanics theory．Further，the authors set up dam age constitutive equation of control fissure．which founds important basis to numerical simulation for control fissure to develop．

Velocities of solid phase and liquid phase in debris flow are one key problem to research on impact and abrasion mechanism of banks and control structures under action of debris flow。Debris flow was simplified as two-phase liquid composed of solid phase with the same diameter particles and liquid phase with the same mechanical features。Assume debris flow was one-dimension two-phase liquid moving to one direction．then general equations of velocities of solid phase and liquid phase were founded in two-phase theory．Methods to calculate average pressures，volume forces and surface forces of debris flow control volume were established．Specially，surface forces were ascertained using Bingham’s rheology equation of liquid phase and Bagnold’s testing results about interaction between particles of solid phase．Proportional coefficient of velocities between liquid phase an d solid phase was put forward，meanwhile，divergent coefficient between theoretical velocity and real velocity of solid phase was provided too．To state succinctly before．method to calculate velocities of solid phase and liquid phase was obtained through solution to general equations．The method is suitable for both viscous debris flow and thin debris flow．Additionally．velocities every phase can be identified through analyzing deposits in-situ after occurring of debris flow．It is obvious from engineering case the result in the method is consistent to that in real-time field observation。

As one weak topic in research of debris flow, abrasion of debris flow shortens obviously application life of control structure composed of concrete. High-speed drainage structure, one of the most effective techniques to control giant debris flow disaster, has shortened one- third application life due to abrasion by debris flow. Based on velocity calculation method founded by two-phase theory, research of abrasion mechanism of debris flow to high-speed drainage structure was made. The mechanism includes both abrasion mechanism of homogeneous sizing and shearing mechanism of particle of debris flow to highspeed drainage trough structure. Further abrasion equations of both sizing and particle were established by Newton movement theory of debris flow. And abrasion amount formula of the high-speed drainage trough structure is set up by dimensional analysis. Amount to calculating in the formula is consistent with testing data in-situ, which is valuable in design of high-speed drainage structure.

Using normal and shear rigid coefficients of intact rock and fracture plane, rigidly normal, shear equivalent rigid coefficients of fissure rock mass are conducted. On the basis of hypotheses of small displacement of rock mass, principle of superposition, irrelevance of strength parameters C and φ and Coulomb theory, formulas to calculate equivalent strength parameters C and φ of equivalent continuous mass from fissured rock mass with anchor piles are given. The achievement is extremely valuable in integral stability analysis of the rock mass slope and important in promoting the research of the rock mass’s constitutive relation.

As one of the most difficult topics in rock mass hydromechanics, seepage free surface plays an important part in slope stability researches. Based on analysis of numerical methods to solve seepage free surface, global composite element iteration ( GCEI ) is presented in this paper . FEM program is made by using GCEI. Calculation shows that not only the program is simple using GCEI, but also the tolerance is higher after 5 iterations.

As one of dominate geological disaster and geomorphologic processes in mountains, debris flow dynamics is essential in designing of structures against debris flow disaster, risk appraisal and mitigation of the disaster. Essential principles of debris flow dynamics are composed of flow velocity, impact and abrasion of debris flow. Based on two-phase theory, both continuum and momentum equations every phase are established. Further, method to calculate velocity of two-phase debris flow is established by introducing parameters M and G0 . Impact forces and duration can be identified by impact formality on banks of debris flow valley or structures. According to abrasion forces of slurry and particles in debris flow, methods to calculate abrasion thickness and velocity are provided primitively. These principles have applied effectively in engineering since 2000.

As one geological disaster in the area of the Three Gorges Reservoir of China, perilous rocks dominate stability of slopes in the area. Most cliffs or steep slopes are alternately composed of inflexible rock such as sandstone and soft rock such as mudstone in the area, and due to different weathering velocities rock cells in soft rock below inflexible rock are usually developed. Any perilous rock belongs to a part of inflexible rock. To appraise the safety of perilous rock, it is essential to approach duration for perilous to form is of interest. In the present paper, authors analyze weathering velocity of rock cell and establish method to calculate length of critical rock cell. Duration for perilous rock to form can be divided into three parts, (1) duration to form critical rock cell, (2) damage duration of control fissure, and (3) fracture duration of control fissure. Further, methods to calculate these durations are established in details based on damage mechanics and fracture mechanics.

As one of dominant geologic disasters in the area of the Three Gorges Reservoir of China, perilous rock displays some features such as much quantity, extensive distribution, bad stability and strong fatalness. The internal reasons is that the stratum composed of soft rock and inflexible rock, steep slope and obvious unloading, while both fissure pressure in control fissure of perilous rock and earthquake force are external reasons for perilous rock to develop. In present paper, the authors establish chained mechanism in views of Geomorphology, and divide the evolution of perilous rock into eight stages. Further, avalanche of perilous rock is divided into three stages, 1) the free falling stage, 2) the initial bounce stage, and 3) the later bounce stage. Methods to calculate moving routine after avalanching of perilous rock are established based on kinematics.

危岩是三峡库区典型的地质灾害类型之一，根据失稳类型本文将危岩分为坠落式危岩、滑塌式危岩和倾倒式危岩三类。其中坠落式危岩和滑塌式危岩的破坏机理主要属于危岩体沿着主控裂隙面剪切破坏，而倾倒式危岩则主要属于危岩体围绕基部倾覆点拉裂转动破坏。实践表明，具有支撑条件时，支撑是极其有效的技术类型，尤其对坠落式危岩和倾倒式危岩更为适用。作用在危岩体上的荷载主要有自重、裂隙水压力和地震力，可构成三种荷载组合，基于支撑体的容许承载力及危岩体的极限平衡理论，本文建立了坠落式危岩的支撑计算方法，建立了倾倒式危岩的支撑-锚固联合计算方法，量化了支撑体尺寸，获得了倾倒式危岩所需的锚杆(索)数量。文中所提出的危岩支撑计算方法两年来已经在三峡库区的数百个危岩体治理中得到成功应用，并被录入《重庆市(三峡库区)滑坡、塌岸、危岩防治工程设计技术规范》中．用于指导三峡库区重庆境内的危岩防治工程。