低液限粉砂土用于高速公路底基层的综合稳定

Comprehensive Stability of Low Limited Liquid Powdered Sand Earth for the Groundwork Layer of Expressway

石灰、粉煤灰稳定土被广泛应用于高速公路底基层 ,它不仅具有经济和环保意义 ,还具有较高的后期强度和较好的水稳定性 用于此种稳定土的土类以粘土或亚粘土为最佳 ,其塑性指数最好在 1 2～ 2 0之间 ,但公路工程的特点决定了使用土类的多样性 淮阴—江都高速公路淮阴段沿线土类多为粉砂土 ,其液限一般在 30 %～ 35%,塑性指数为 8～ 1 2 ,小于 0 .0 0 2mm的粘粒含量少、活性低、粘聚性差 ,仅用石灰、粉煤灰来进行综合稳定 ,早期强度较低 ,成型质量较差 ,难以完全达到规定的强度和稳定性要求 ,这就要求采取一定的技术措施来加以改善 用适量水泥、石灰、粉煤灰进行综合稳定就是针对粉砂土的不利因素提出的一种有效措施 文中通过不同的材料组成比例与强度的对应关系 ,浅析了掺入水泥前后混合料强度形成机理各自的特点 ,再现了石灰、粉煤灰稳定粉砂土时 ,掺入水泥能明显提高混合料早期强度及水稳定性的结论 除此以外 ,作者通过施工现场质量的检测与控制的实践和探索 ,提出配合比是稳定土质量的关键因素 ,应严格掌握控制 。

The stable earth of limestone and fly ash is widely used for the groundwork layer of expressway. It is advantageous to economy and environment protection as well as higher later strength and better water stability. For this purpose, the clay or mild clay is the best with its plasticity index between 12 to 20. But the features of highway construction determine the varieties of earth to be used. Most of the earth used for the expressway from Huaiyin to Jiangdu is powdered sand earth with a liquid limit of 30%～35% and the plasticity index of 8～12.This kind of powdered sand earth greatly lowers the content of clay granules that are less than 0.002mm in diameter and of low activity and poor cohesiveness . If only limestone and fly ash are used to strengthen the comprehensive stability, the early strength is lower and the shaping quality is poorer. It is very difficult to fully meet the requirements of regulated strength and stability, so it is required that certain technical measures be taken to improve the strength and stability. It is just an effective measure to use suitable cement, limestone and fly ash for comprehensive stability of powdered sand earth. Through the corresponding relationship between different ratios of material composition and strength, the author analyses the mechanism and features of strength forming of the mixed materials before and after the mixing of cement.The result shows that if cement is properly mixed with limestone and fly ash to stabilize the powdered sand earth, the early strength and water stability of the mixed materials is obviously improved. Besides , through practices of quality inspection and quality control at the jobsite, the author puts forward that the mixing ratio is the key factor that affects the quality of stable earth. Therefore ,the formulating ratio should be under strict control. At the same time, the process of construction and the method of inspection for mixing ratio are briefly introduced.