邯郸强膨胀土三向膨胀力特性试验研究

对在不同干密度、初始含水率、温度下的邯郸强膨胀土和复合改性后的膨胀土进行三向膨胀力试验研究。结果表明,在试验条件范围(干密度:1.2,1.35,1.5,1.65 g/cm~3;初始含水率:15%,18%,21%,24%;温度:20℃,35℃,45℃,55℃,65℃)内,竖向与水平向膨胀力的比值随干密度增加而增加,干密度等于1.2g/cm~3时,比值接近1;干密度是决定平衡时间的关键因素,干密度越大的试样膨胀平衡时间越长,且所有试样平衡时间都在3000 min内;在室内常温(20℃左右)和初始含水率相同时,竖向膨胀力随干密度呈指数关系递增;相同温度和干密度下,随着初始含水率增加,三向膨胀力皆呈线性减小的规律,且三向膨胀力与初始含水率关系曲线的斜率随干密度线性递增;经过0.8%PVA(聚乙烯醇)+5%KCl(氯化钾)的混合溶液改性,并添加0.6%聚丙烯纤维后的土样竖向膨胀力下降33.3%,0.8%PVA+4%CaO(氧化钙)的混合溶液改性的土样竖向膨胀力下降16.7%。未改性和经过0.8%PVA+4%CaO的混合溶液改性的土样竖向膨胀力随着温度的升高而减小,经过0.8%PVA+5%KCl的混合溶液改性,并添加0.6%聚丙烯纤维后的土样随着温度升高竖向膨胀力先增加,温度大于45℃后逐渐减小。

Experimental study on three-dimensional swelling pressure of highly expansive clay in Handan district of China

The three-dimensional swelling pressure tests on highly expensive soil are carried out under different dry densities, initial moisture contents and temperatures using composite modification methods. The results show that the ratio of vertical swelling pressure to horizontal swelling pressure increases with the increase of dry density in the range of test conditions (dry densities of 1.2, 1.35, 1.5 and 1.65 g/cm³, initial moisture contents of 15%, 18%, 21% and 24%, temperatures of 20℃, 35℃, 45℃, 55℃ and 65℃). The ratio is close to one when the dry density is 1.2 g/cm³. Moreover, the dry density is the key factor that determines the swelling pressure equilibrium time. The larger the dry density, the longer the equilibrium time. However, the swelling pressure equilibrium time of all samples is within 3000 minutes. The vertical swelling pressure of the expansive soil increases exponentially with the enlargement of the dry density at room temperature of 20℃ when the initial moisture contents are the same. Under the same temperatures and dry densities, the three-dimensional swelling pressures decrease linearly with the increase of the initial moisture content. Moreover, the slope of the relation curve increases linearly with the dry density. The vertical swelling pressure of the soil decreases by 33.3%, which is treated by 0.8% polyvinyl alcohol (PVA) with 5% potassium chloride (KCl) mixture solution and 0.6% polypropylene fiber, and that of the soil reduces by 16.7%, which is treated by 0.8% PVA with 4% lime (CaO) mixture solution. The vertical swelling pressure of the unmodified soil and the modified sample treated by 0.8% PVA with 4% CaO mixture solution decreases with the rise of the temperature. However, the vertical swelling pressure of the soil samples increases with the rise of temperature, and gradually decreases when the temperature exceeds 45℃ after modification by 0.8% PVA with 5% KCl mixed solution and 0.6% polypropylene fiber.