类土质岸坡雪崩式破坏机制研究——以三峡库区龚家方岸坡为例

Study on Avalanche Failure Mechanism for Soil-Similar Bank:Taking Gongjiafang Bank of Three Gorges Reservoir Area as an Example

【目的】水库岸坡破坏机制是库岸地质减灾的重要科学问题。【方法】以三峡库区龚家方岸坡为例,采用现场勘查和模型实验方法,探讨类土质岸坡破坏机制问题。【结果】现场勘查结果表明,类土质岸坡破坏的地质基础包括两方面:一是岸坡由灰岩、泥灰岩、白云岩、页岩、片麻岩、板岩等并富含蒙脱石和伊利石亲水性矿物的碎裂岩体组成;二是岸坡卸荷作用强烈,卸荷结构面岩桥区段是岸坡破坏的关键环节。模型实验结果表明,类土体渗透性良好,水库蓄水初期库水进入岸坡后地下水在类土体空隙内产生明显的紊流作用,孔隙水压力波动特征明显。【结论】水库蓄水浸泡条件下岸坡卸荷结构面岩桥区段抗剪强度参数劣化作用和水库蓄水初期岸坡内孔隙水压力波动作用是类土质岸坡发生雪崩式破坏的物理机制。

[Purposes]It is one of important scientific problems in geological disaster mitigation for failure mechanism of reservoir bank.[Methods]Taking Gongjiafang bank in Three Gorges reservoir area as an example,the authors discuss failure mechanism of soil-similar bank using observation in field and model experiments.[Findings]Observation in field illustrate that geological conditions include two spheres for soil-similar bank to failure,one is that the bank is composed of brittle rocks such as limstone,mudstone,dolomite,shale,gneiss,slate,in particular,there are a large quantity hydrophilic clay minerals such as montmorillonite and illite in weathering materials from these rocks,another is strong unloading in bank,and the rock bridge zone of unloading structure is the key agent for the bank to rupture.Model experiments demonstrate that the permeability of soil-similar rock is positive,and turbulence is triggered in porosity of soil-similar rock after immersion of water at the initial impoundment of the reservoir.Simultaneously,fluctuation of pore pressure in soil-similar bank are hardly in evitable by the turbulence.[Conclusions]physical avalanche mechanism of soil similar bank manifests two facets,one is deterioration of shear strength parameters of rock bridge zone of unloading structure in bank under impoundment of reservoir,another is the fluctuation of pore pressure at the initial impoundment.Further,the paper approaches the mechanism for the fluctuation of pore pressure in soil similar bank.