引江济淮河道膨胀土边坡换填层余料工程特性研究

引江济淮河道工程沿线膨胀土分布范围广、厚度大、天然含水率高,河道膨胀土边坡采用改性土换填方案防护,填筑改性土层超宽施工产生大量削坡余料,余料再利用对于工程进度和造价有重要影响。通过试验研究发现,相对于原生改性土,余料的最优含水率增大,容易压实,有利于现场压实度控制。余料的直接剪切强度和原生改性土差别不大,剪切破坏表现为明显的超固结土特征。余料的强度随养护时间无明显的变化。5%水泥改性土削坡余料的膨胀性远小于弱膨胀土的自由膨胀率控制指标40%,随时间呈对数衰减规律。5%水泥改性土削坡余料的渗透系数为10-5数量级,大于原生改性土,换填层渗透系数控制指标应根据换填层厚度和气候条件综合分析确定。削坡产生余料的体积量与坡长和坡率有关,占比大于20%。

Engineering characteristics of surplus materials of replacement layer of expansive soil slope of water diversion from Yangtze River to Huaihe River

There exists an expansion of expansive soils with large thickness and high moisture content along water diversion project from Yangtze River to Huaihe River. In this study, the modified expansive soil is used as a cover to protect the canal slope. The large-scale project results in a large quantity of construction surplus materials which are difficult to be disposed. Thus to reuse the surplus materials has an important effect on the progress and the cost of the project. This study shows that the optimum moisture content of the surplus materials is higher than that of the native modified soil, which is easier to be compacted and is more advantageous for in-site compaction control. There is little difference between direct shear strength characteristics of the surplus materials and the native modified soil. The shear failure exhibits characteristics of over-consolidated soils. The strength of the surplus materials has no obvious change with the curing time. The degree of expansion of the surplus materials with cement of 5% is far less than that of the weak expansive soil and exhibits logarithmic decay with time. The coefficient of permeability of the surplus materials with cement of 5% is in the order of 10^-5, which is larger than that of the native modified soil. The control index of permeability coefficient of the replacement layer should be comprehensively analyzed and determined according to the thickness of the replacement layer and climatic conditions. The volume of the surplus materials produced by slope cutting is related to the slope length and slope ratio, accounting for more than 20%.