The Middle Route Project for South-to-North Water Transfer, which consists of a long artificial open channel and various hydraulic constructions, is a big water conveyance system. A numerical modeling of water conveyance in the ice period for such large-scale and long distance water transfer project is developed based on the integration of a river ice model and an unsteady flow model with complex inner boundaries. A simplified method to obtain the same flow discharge in the upstream and downstream of the structure by neglecting the storage effect is proposed for dealing with the inner boundaries. According to the measured and design data in winter-spring period, the whole ice process, which includes the formation of the ice cover, its development, the melting and the breaking up as well as the ice-water dynamic response during the gate operation for the middle route, is simulated. The ice characteristics and the water conveyance capacity are both analyzed and thus the hydraulic control conditions for a safety regulation are obtained. At last, the uncertainties of some parameters related to the ice model are discussed.
旋流环形堰竖井泄洪洞是一种新型的环境友好的内消能工,跟传统环形堰竖井泄洪洞相比,泄洪洞的流态和消能防蚀机理明显不同。作为一种新型布置形式,其复杂的水流特性并不是十分清楚。依托于广东清远抽水蓄能电站下水库泄洪洞工程,基于RNG k-ε双方程湍流数学模型,并结合VOF(Volume Of Fluid)方法,对下库旋流环形堰竖井泄洪洞进水口、竖井旋流泄洪洞、出口的复杂水流进行了三维数值模拟,并对部分水力参数的特性进行了解析计算,获得了流态、压力、流速、空化数等水力要素的变化规律。模拟结果表明,数值计算结果与物理模型试验成果吻合较好。并通过数值模拟验证了该新型内消能工的泄流能力和高消能效率。
The closed form solutions of the stress and displacement in strain softening rock mass around a newly formed cavity are derived with a three step-wise elasto-plastic model. Hoek-Brown criterion is adopted as the yielding criterion of rock mass. Damage factors are proposed to account for degradation of the material parameters to reflect the degree of strain softening. The surrounding rock mass around the cavity is divided into three regions: elastic region, strain softening region and residual state region. The analytical solutions of stress, strain, displacement and radius of each region are obtained. The effects of the strain softening and shear dilatancy behavior on the results are investigated with parametric studies. The results show that the radii of the residual state region and strain softening region in the surrounding rock mass with higher damage degree are larger. The radii of the residual state region and strain softening region are 1-2 times and 1.5-3 times of the cavity radius, respectively. The radial and tangential stresses decrease with the increase of the damage factor. The displacement of the cavity wall for the case with maximum plastic bulk strain is nearly twice than that with no dilation. Rock mass moves more toward the center for the case with larger damage factor and shear dilation. The area of the plastic region is larger when the damage factors are considered. The displacements in the surrounding rock mass increase with the increase of the damage factors and shear dilation factors. The solutions can be applied to the stability analysis and support design of the underground excavation.
The Karhunen-Loeve(KL) expansion and probabilistic collocation method(PCM)are combined and applied to an uncertainty analysis of rock failure behavior by integrating a selfdeveloped numerical method(i.e., the elastic-plastic cellular automaton(EPCA)). The results from the method developed are compared using the Monte Carlo Simulation(MCS) method. It is concluded that the method developed requires fewer collocations than MCS method to obtain very high accuracy and greatly reduces the computational cost. Based on the method, the elastoplastic and elasto-brittle-plastic analyses of rocks under mechanical loadings are conducted to study the uncertainty in heterogeneous rock failure behaviour.
Pengzhi PanFangsheng SuHaijun ChenShilin YanXiating FengFei Yan
