初次蓄水土质心墙坝水力劈裂分析理论及其应用

The hydraulic fracturing of earth-rock damwith centralsoil core is paid close attention by engineering and academia. Our goal is to establish a mathematical model of quantitative analysis for the hydraulic fracturing problem, so as to eventually reach for anti-crack design of core rockfill dams. The soil core is in a saturated-unsaturated state during the course of construction and initial impoundment and hydraulic fracture always occurres in the initial impounding period. In view of these facts, considering the soluble of the pore air, and highlighting the existence of the pore air blocking effection on the movement of the pore water, a soil consolidation model of three-phase medium is to be established for the core. The consolidation theory could be universal for saturated and unsaturated soils. On this foundation, Consolidation calculations would be done to a project example which has been deduced dam break due to hydraulic fracturing in the course of construction process and initial impoundment. The hydraulic fracturing mechanism of the core would be studied. And a criterion for judgement of the hydraulic fracturing could be found.Forthermore,a comprehensive study will be conducted to the factors influencing the hydraulic fracturing of the rockfill dam with clay core in initial impoundment.

土质心墙坝的水力劈裂问题是坝工界广泛关注、颇具争议的论题。课题旨在建立可以进行土质心墙水力劈裂问题定量分析的数学模型，以便最终能用于心墙坝的抗裂设计。鉴于填筑及初次蓄水过程土质心墙处于饱和-非饱和状态以及水力劈裂都发生在初次蓄水初期的事实，强调孔隙空气的存在及其可溶性对非饱和土固结特性的影响，试图通过孔隙空气的可溶性（包括溶解或脱溶过程），采用统一的方法处理饱和土与非饱和土固结问题，建立心墙非饱和土固-液-气耦合三相介质固结模型，采用土质心墙坝水力劈裂问题非饱和土耦合固结计算有效应力分析有限元法，分析心墙水力劈裂发生的力学机理，确定水力劈裂的判断准则，研究水力劈裂的主要影响因素，为土质心墙坝设计方案的准确制定提供理论依据。

质心墙坝的水力劈裂问题是坝工界广泛关注、颇具争议的论题。本课题通过离心机试验，研究了运行期坝体中水力劈裂问题，离心加速度加载至50g时发生水力劈裂现象，说明施工阶段碾压质量、裂隙等为初次蓄水发生劈裂提供条件，而快速上升水位产生的水压力提供了劈裂力。.土石坝施工和运行期无法避免裂缝的发生，研究了水力劈裂的力学机理，劈裂过程中包含张拉和剪切两种破坏类型，围压和心墙粘聚力是影响土体劈裂起劈压力的主要因素。借助断裂力学研究了I型、II型裂缝的发展问题。.蓄水初期，坝内孔隙水压力没有及时消散，发生水力劈裂时，应考虑气压上升的影响，鉴于填筑及初次蓄水过程土质心墙处于饱和-非饱和状态以及水力劈裂都发生在初次蓄水初期的事实，研究水力劈裂问题应该建立在非饱和土不排水剪的基础上确定计算参数，真实反映劈裂问题。.鉴于填筑及初次蓄水过程土质心墙处于饱和-非饱和状态以及水力劈裂都发生在初次蓄水初期的事实，均质坝浸润线以上土体呈非饱和状态，孔隙水压力和孔隙气压力随土体变形而变化以及随时间增长而消散，应用流体连续性方程和土体平衡等方程，以双压强变量、土骨架位移分量作为基本变量以广义有效应力和吸力作为应力状态变量是非饱和土固结状态变量，建立了土固-液-气耦合三相介质非饱和土固结模型，采用土质心墙坝水力劈裂问题非饱和土耦合固结计算有效应力分析有限元法，分析心墙水力劈裂发生的力学机理，确定水力劈裂的判断准则，研究水力劈裂的主要影响因素，为土质心墙坝设计方案的准确制定提供理论依据。