Expansive soil is a kind of high plastic clay whose clay composition is mainly composed of strong hydrophilic minerals. It is hard or hard plastic state, and its strength is generally high. It has the characteristics of water absorption expansion, water loss shrinkage and repeated expansion and contraction deformation, strength attenuation after immersion, and development of dry shrinkage cracks.

我国膨胀土分布广泛，广西、云南、湖北、江苏、广东等地均有不同范围的分布。利用膨胀土作为建筑物的地基时，若在施工中没有采取必要的措施进行地基处理，往往会给建筑物带来危害，主要表现为建筑物的基础外移、房屋开裂(山墙倒八字形缝，外纵墙下部水平缝)、地坪开裂等事故。

Expansive soil is widely distributed in China, Guangxi, Yunnan, Hubei, Jiangsu, Guangdong and other places. When using expansive soil as the foundation of a building, if necessary measures are not taken for foundation treatment in the construction, it will bring harm to the building, mainly manifested in the accidents of building foundation moving outward, house cracking (gable inverted splayed joint, horizontal joint of lower part of outer longitudinal wall), floor cracking, etc.

以南宁为例，据有关资料显示，南宁地区膨胀土成分含有较多的亲水性强的---、伊利石等膨胀性物质，黏粒含量高，粒径＜0.002mm的胶体颗粒含量＞25%，塑性指数ip在17～32之间，自由膨胀率超过40%，因此该地区的膨胀土具有非常明显的湿胀干缩效应。

Taking Nanning as an example, according to the relevant data, the expansive soil in Nanning area contains more expansive materials with strong hydrophilicity, illite, etc., the content of clay is high, the content of colloidal particles with particle size less than 0.002 mm is more than 25%, the plasticity index IP is between 17 and 32, and the free expansion rate is more than 40%. Therefore, the expansive soil in Nanning area has a very obvious effect of wet expansion and dry shrinkage.

由于上部作用荷载不同，使得地基土体在强烈的胀缩循环过程中受到不同程度的---，导致基础产生不均匀沉降，从而使得上部轻型结构中产生超出墙体承载能力的附加拉力和剪力，墙体出现裂缝。据不完全统计，强夯机，我国在膨胀土地区修建的各类工业与民用建筑物，因地基土胀缩变形而导致损坏或破坏的超过1000万m2。

Due to the different loads acting on the upper part, the foundation soil is subjected to different degrees of expansion and contraction cycle, which leads to uneven settlement of the foundation, resulting in the additional tension and shear force exceeding the bearing capacity of the wall in the upper light structure, and the wall cracks. According to incomplete statistics, dynamic compaction machine, all kinds of industrial and civil buildings built in expansive soil area in our country, more than 10 million M2 are damaged or destroyed due to the expansion and shrinkage deformation of foundation soil.