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在强度低,压缩性高的地基上修筑路基,往往会发生路基失稳或过量沉陷,导致公路破坏或不能正常使用的情况,这种软弱土层,就是软土地基。地基中常见的软土,一般是指处于软朔或者流朔状态下的粘性土。其特点是天然含水量大、孔隙比大、压缩系数高、强度低,并具有蠕变性、触变性等特殊的工程地质性质,工程地质条件较差。这种土质如在施工中出现在路基填土或桥涵构造物基础中,最佳含水量不易把握,极难达到规定的压实度值,满足不了相应的密实度要求,在通车后,往往会发生路基失稳或过量沉陷。其危害性显而易见,故禁止采用。软土地基下沉的一个主要原因是软土地基的沉降,包括瞬时沉降、固结沉降和次固结沉降三部分。
In the low strength, high compressibility of the foundation on the construction of subgrade, often occurs subgrade instability or excessive settlement, leading to road damage or failure to use the normal situation, this soft soil is soft soil foundation. Soft soil commonly found in the foundation, generally refers to the soft moon or stream Shuo state cohesive soil. It is characterized by a large natural water content, large void ratio, high compressibility, low strength, and has special engineering geological properties such as creep and thixotropy. The engineering geological conditions are poor. If this kind of soil appears in the foundation of roadbed filling or bridge and culvert structure in construction, the optimum moisture content is not easy to grasp, it is extremely difficult to reach the required degree of compaction, which can not meet the corresponding compaction requirements. Subgrade instability or excessive subsidence occurred. Its harmfulness is obvious, so it is forbidden to adopt. One of the main causes of soft ground subsidence is the settlement of soft ground, including instantaneous settlement, consolidation settlement and sub-consolidation settlement.