Soft Soil Improvement by Vertical Sand piles

砂井排水(1)当考虑约25米厚的粘土层时，发现引起局部排水性状变化的土壤渗透性范围为10^；-7厘米/秒k 10^；-4厘米/秒。(2)当土壤渗透率在这个特定范围内时，荷载强度越大，部分排水效果越值得期待。(3)在有限的土壤渗透率范围内，在特定的荷载强度下观察砂井排水的效率。挤密砂桩(1)竖向挤密砂桩软土的承载能力受荷载刚度的影响很大。当考虑通过刚性基础施加荷载时，砂桩的排水/膨胀条件比不排水/不膨胀条件提供更大的承载能力。另一方面，在路堤加载等柔性荷载作用下，不排水条件下的地基承载力要大于完全排水/膨胀条件下的承载力。(2)在考虑相对较低的置砂率时，应正确评价砂桩安装引起的位移和固结引起的粘土不排水强度的提高。

Sand Drains(1)The range of soil permeability which yields the variation of partial drain behavior was found10^<-7>cm/sec k 10^<-4>cm/secwhen a clay deposit of about 25 meters thick is considered.(2)When soil permeability lies on this particular range the bigger the load intensity, the more the partial drain effect should be expected.(3)The efficiency of sand drains is to be observed in a limited range of soil permeability and under a particular magnitude of load intensity.2. Sand Compaction Piles(1)The bearing capacity of soft clay with vertical sand compaction piles is extremely influenced by the stiffness of applied load. When load application through a rigidfooting is considered fully drained/swelling conditions for sand piles provide biggerbearing capacity than undrained/no swelling conditions. On the other hand, whenflexible load application such as embankment loading is the case, undrained conditionsgive bigger bearing capacity than fully drained/swelling condition.(2)The increase of the undrained strength of clay due to displacement and consolidation by sand pile installation should be correctly evaluated when relatively low sand replacement ratio is considered.