回填工况下地下粮仓的摩擦力分析

Friction Analysis of Underground Silos during Backfilling

为了分析回填工况下地下粮仓在地下水作用时的摩擦力变化情况,设计了3个材质为2 mm厚钢板、仓底倾角为35°,直径分别为400 mm、500 mm、600 mm的模型筒仓A、B、C,进行了两种工况的6组注水试验。试验结果表明,模型筒仓顶部位移计数据发生突变时,工况a中,模型筒仓A、B、C水位分别为41.40 mm、39.80 mm、35.00 mm;工况b中,模型筒仓A、B、C水位分别为40.60 mm、39.00 mm、33.10 mm(p<0.05)。静止阶段,模型筒仓A、B、C顶部支反力不变。上浮阶段,模型筒仓顶部支反力发生突变,工况a时,模型筒仓A、B、C水位-支反力曲线拐点水位分别为37.10 mm、27.00 mm、21.00 mm;工况b时,模型筒仓A、B、C水位分别为37.10 mm、30.05 mm、24.00 mm。由于静摩擦力的影响,模型筒仓的位移计变化滞后于支反力。静止阶段,工况a中的最大静摩擦力分别为206.17 N、316.81 N、364.16 N,均大于工况b的静摩擦力197.61 N、310.82 N、352.96 N。但其随水位的增加速度基本一致(p<0.05)。上浮阶段,工况a、b的摩擦力均迅速下降,并趋于稳定。实际工程中,考虑有利因素的地下粮仓抗浮设计,可采用上浮阶段的摩擦力设计。

To investigate the variations in friction in underground silos due to groundwater during backfilling,three silo models,namely,A,B,and C,with three different diameters of 400 mm,500 mm,and 600 mm were designed.All these models were composed of 2 mm thick steel plates with a bottom inclination angle of 35°.Six water injection tests were conducted under two different backfilling conditions.The experimental results demonstrate that when there are sudden displacement changes at the top of the silos,the water levels of models A,B,and C are 41.40 mm,39.80 mm,and 35.00 mm,respectively,under backfilling condition a.Meanwhile,the water levels become 40.60 mm,39.00 mm,and 33.10 mm under backfilling condition b(p<0.05).In the stationary phase,the reaction forces at the top of the models A,B,and C remain unchanged.In the floating phase,the reaction force at the top of the silos abruptly changes.Under backfilling condition a,the water level-reaction force curves of models A,B,and C result in inflection points at water levels of 37.10 mm,27.00 mm,and 21.00 mm,respectively.Under condition b,the inflection points are observed at water levels of 37.10 mm,30.05 mm,and 24.00 mm,respectively(p<0.05).Because of the static frictional force,the displacement changes measured by the gauge lag behind the variation in reaction forces.In the stationary phase,under condition a,the maximum static frictional force of the models is 206.17 N,316.81 N,and 364.16 N,respectively.These values are all greater than those under condition b,which are 197.61 N,310.82 N,and 352.96 N,respectively;yet,the water levels of the models under two different conditions increase at nearly the same rate(p<0.05).In the floating phase,frictional force reduces rapidly under both conditions and then levels off gradually.In actual engineering projects,favorable anti-floating underground silo designs can be adopted by integrating the frictional force variations in the floating phase.