Abstract: In view of the shortcomings of traditional basement anti-floating methods,we discussed the basic principle and the corresponding construction measures of draining decompression.We also analyzed the factors affecting the anti-floating effect with orthogonal experiments compared with numerical simulation.The factors include the width of backfill,the spacing of drainage holes,the compaction degree of backfill,and the disturbance degree of the underlying at the bottom of the basement.Finally,we calculated the influence order and weights of various factors using residual analysis method and analytic hierarchy process.Results show that compared with conventional methods,draining decompression has obvious anti-floating effect by changing passive anti-floating to active anti-floating.Moreover,it is convenient to construct,and the cost is low.The order of factors according to the influence is as follows:compaction degree of backfill>width of backfill>spacing of drainage holes>disturbance degree at the bottom of basement,and the corresponding weights are 0.55,0.27,0.15,0.03,respectively.The sum of the first three factors is up to 0.97.As a result,we should try to reduce the spacing of holes,the width and the water permeability of the backfill to achieve good anti-floating effect in engineering practice.Besides,we should also limit the parameters of these three factors reasonably in order to achieve the best effect of lowering water level according to specific engineering conditions.The research method provides an important reference for the design and construction of the anti-floating method by draining decompression.

Key words: anti-floating method by draining decompression, drainage holes, orthoganal experiment analysis, width, compaction degree, disturbance degree