Technical Study On Oil Tank Foundation Treatment With Bedding Pre-elevating And Step Water-filling Pre-compressing

Five floating roof oil tanks with volume 2 104m3 are designed to be constructed at Shuguang Pump Station possessed by Liaohe Oil Field, which is located at Liaohe Delta alluvial plain. This engineering filed is featured with complicated topography. The oil tank foundation soil is horizontally-layered, including four layers: medium dense-dense clay, interbedding of find sand and clay, fine sand sandwiching clay and fine sand. It is demonstrated by geologic survey data that the bearing capability and deformation of natural foundation are out of the scope of the required values, which means the natural foundation has to be treated.This dissertation is for the engineering project mentioned above. The papers and technical reports about the oil tank foundation treatment shows that in our country abundant experiences have been built up in dealing with the soft clay foundation, while there were few cases for sand foundation. Analyzing the geological condition, the author proposed that the foundation soils at Shuguang Pump Station belong to high-permeability sand layers. Based on comparison of several technical schemes, the method of sand bedding pre-elevating and step water-filling pre-compressing is adopted. So the dissertation is consist of two parts: (1) the applicability study for the method of sand bedding pre-elevating and step water-filling pre-compressing, including numerical analyses for the thickness of sand bedding, the consolidation, settlement and stability of foundation, drainage, possibility of foundation liquefaction under seismic loading, et al. (2) monitoring at construction stage and checking the effect of foundation treatment, including the measurements of the settlement velocity and non-uniform settlement of ring beam under the tank, pore pressures and horizontal displacements in foundation, the pressure distribution at the bottom of oil tank and the strength increase of soils.It is observed that the numerical results corporate well with the data monitored, and the bearing capability and settlement of foundation consolidated gets to the required values. Over traditional methods used in this region, method of sand bedding pre-elevating and step water-filling pre-compressing has advantages in shorting construction period, simplifying construction. Furthermore, this method solves the difficulty induced by constructing at rain season. It is believed that conclusions from the dissertation will be helpful for the oil tankbuilding at Liaohe Delta region in the future.