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本文介绍了砂壳坝抗震加固的一种新方法——振动水冲法。山东省兴旺坝振冲加固试验表明,砂壳坝的振冲加固与地基振冲加固不尽相同,砂壳坝中存在广阔的非饱和区,而且振冲过程中存在“斜坡效应”,从振冲时坝的动力反应观测资料的分析得知,振动加速度、超静孔隙水压力均随振源距的增大而急剧减小,它们与振源距均呈幂函数关系。探索振冲加固机理得知,饱和松砂的振冲加密是通过三个作用实现的:①径向冲击位移将砂挤入坡内;②引起超静孔隙水压力使砂坡液化Q③固结。本文提出了一套振冲工艺参数,利用这些参数并使振冲区砂壳处于饱和状态是提高振冲效果的关键。这也是兴旺坝壳的加固效果能达到相对密度0.8左右和标贯击数达到40击以上的重要前提。文中还简要地叙述了兴旺坝振冲施工的主要经验,说明这个方法安全、方便、经济,是抗震加固已建的松散砂壳坝的有效方法。
In this paper, a new method of seismic reinforcement of sand-shell dams is introduced. The vibrofitation and reinforcement test of Xingwang Dam in Shandong Province shows that the vibroflotation of the sand-shell dam is not the same as that of the ground vibroflotation. There is a wide non-saturated area in the sand-shell dam, and there is a “ramp effect” in the vibroflotation process. The analysis of the dynamic response observation data of Chongshiba shows that the vibration acceleration and the excess pore water pressure decrease sharply with the increase of the vibration source distance, and they have a power function relationship with the vibration source distance. The mechanism of vibroflotation and reinforcement was explored. The vibration of the saturated loose sand was encrypted through three actions: 1 The radial impact displacement squeezed the sand into the slope; 2 The extra-static pore water pressure caused the sand slope to liquefy and Q3 consolidated. This paper proposes a set of vibratory process parameters. Using these parameters and making the shell in the vibrating zone saturated is the key to improving the vibroflotation effect. This is also an important prerequisite for the strengthening effect of the Xingwang dam shell to reach a relative density of about 0.8 and a standard strike number of 40 hits or more. The paper also briefly describes the main experience of Xingwangba vibroflotation construction, and shows that this method is safe, convenient, and economical. It is an effective method for seismically strengthening the existing loose sand-shell dam.