Study On The Stability Against Floatation Of Channel On Complex Ground And Optimization Of Seepage Control

In the Huangyou part of the first stage of middle route of South-to-North water transfer project, the foundation of channel is mostly composed of pebbles. Due to the high permeability of pebble layers, in the flood season when the channel has been built before water storage, the groundwater level rises rapidly. Thus it produces uplift pressure to the bottom plate of channel and there is anti-floating problem. In order to ensure the safety of project, some measures have been taken to deal with this problem in the proposal design. To increase the cover weight, the pebbles in certain depth of channel foundation are removed, and the cohesive soil is backfilled. Furthermore, to diminish the osmotic pressure at the bottom of channel soft penetrated pipes used as drainage are placed under back-filling soil, and then the infiltration water flows into the channel through PVC pipes and concrete pipes. With those measures, it is unknown that whether the channel can remain stable and it is necessary for further study. So the three dimension steady seepage of the typical channel of Huangyou part is calculated based on large finite software ABAQUS. Besides, the analysis of stability against floatation of channel is made in this paper. And the research on the optimization design of seepage control is carried out by the method of orthogonal experimental design. The specific work of this article is as follows:(1)The basic theory of3-d stable seepage calculation and method of seepage analysis based on ABAQUS are introduced. Air element method is used to simulate the drain pipes. What’s more, the effect of various factors, such as head on two banks, backfill soil, on the stability against floatation of channel is analyzed. And the influence law of them on pore pressure at the backfill soil bottom is found.(2)According to the theory of "equivalent hydraulic conductivity", combining a practical project, a method of giving permeability coefficient to pipes is put forward. On this basis, in the most dangerous combination, the three dimension steady seepage of the typical channel of Huangyou part is analyzed. The results show that, the stability safety against floatation to the original design meets the requirement. Moreover, the drainage-piping in the foundation of channel makes evident effects on seepage control.(3) By the method of orthogonal experimental design, taking the security and economy into consideration, the research on the optimization design of seepage control of the typical channel is carried out. Meanwhile, an optimization design is proposed.