The leasing manufacturer of dynamic compaction machine elaborated the concept of soft soil, summarized the characteristics of soft soil foundation, and combined with relevant technical specifications and construction experience, introduced the common soft soil foundation treatment methods such as dynamic compaction method, rolling method and compaction method, drainage consolidation method, soil replacement cushion method, compaction method and vibroflotation method, and their respective application scope, so as to provide reference for construction personnel.

1.软土的概念

1. Concept of soft soil

软土是指以水下沉积的软弱粘性土或淤泥为主的地层,有时也有少量的腐泥或泥炭层。软土、沼泽的划分为软粘土、淤泥质土、淤泥、泥炭质土及泥岩五种类型。江西强夯习惯上常把淤泥、淤泥质土、软粘土总称为软土,而把有机质含量高的泥炭、泥炭质土总称为沼泽。

Soft soil refers to the stratum mainly composed of soft cohesive soil or silt deposited underwater, sometimes with a small amount of sapropel or peat layer. Soft soil and swamp can be divided into five types: soft clay, muddy soil, silt, peat soil and mudstone. In Jiangxi Province, silt, muddy soil and soft clay are usually called soft soil, while peat and peat soil with high organic matter content are called swamp.

2.软基特性软土地基一般是指在静水或缓慢水流环境中沉积的饱和粘性土,并常夹有泥炭、贝壳及生物残骸。特性如下:

2. Characteristics of soft soil foundation soft soil foundation generally refers to the saturated cohesive soil deposited in still water or slow flow environment, and often contains peat, shells and biological debris. The characteristics are as follows:

1)天然含水量和孔隙比大。江西强夯天然含水量高,一般大于35%,接近或大于液限;天然孔隙比一般大于1,多数在1.0~2.0之间。

1) The natural water content and void ratio are large. The natural water content of dynamic compaction in Jiangxi is high, generally greater than 35%, close to or greater than the liquid limit; the natural void ratio is generally greater than 1, mostly between 1.0 and 2.0.

2)透水性差。软土亲水性强,透水性差,具有明显的方向性,软土的粘粒含量、有机质含量和液限越大,渗透系数就越小,k一般为10-7cm/s~10-8cm/s,因此决定了内部水分渗水条件不良,对地基排水不利。

2) The water permeability is poor. Soft soil has strong hydrophilicity, poor permeability and obvious directionality. The greater the clay content, organic matter content and liquid limit of soft soil, the smaller the permeability coefficient, K is generally 10-7cm / S ~ 10-8cm / s. therefore, the internal water seepage condition is poor, which is unfavorable for foundation drainage.

3)压缩性高。江西强夯软土由于孔隙比大,土粒间连接结构不稳定,具有高压缩性的特点,且随液限的增加而增加。

3) High compressibility. Due to the large void ratio and unstable connection structure between soil particles, the dynamic compaction soft soil in Jiangxi Province has the characteristics of high compressibility, which increases with the increase of liquid limit.

4)抗剪强度低。江西强夯不排水剪切时,内摩擦角接近于0,一般情况下,内摩擦剪应力小于19.92kPa,排水剪切时,抗剪强度随固结

4) The shear strength is low. In general, the internal friction shear stress is less than 19.92kpa, and the shear strength increases with consolidation

5)触变性和蠕动性大。江西强夯软土结果未被破坏以前具有一定的结构强度,一经扰动,强度迅速降低,但随静置历时增加,强度将逐渐恢复。

5) Thixotropic and peristaltic. The results of dynamic compaction of soft soil in Jiangxi Province have a certain structural strength before it is damaged. Once disturbed, the strength decreases rapidly, but with the increase of standing time, the strength will gradually recover.