风化砂改良膨胀土膨胀特性试验研究

结合湖北省宜昌市小溪塔至鸦鹊岭一级公路改建工程及风化砂改良膨胀土路基施工项目,对膨胀土掺入不同比例的风化砂配制试件,进行自由膨胀率、无荷膨胀率、25 kPa和50 kPa有荷膨胀率以及膨胀力的试验研究,得到了不同掺砂比例下膨胀土的膨胀率和膨胀力指标。研究发现：掺砂对抑制膨胀土的膨胀是有效的,经过风化砂改良的膨胀土的自由膨胀率小于35%,达到了路基施工规范的要求。不同的掺砂量对改良膨胀土的膨胀指标有着显著的影响：当掺砂比例为10%时,自由膨胀率、膨胀力降低最为显著；当掺砂比例为40%~50%时,25 kPa有荷膨胀率的变化最为明显；掺砂比例为30%~40%,50 kPa有荷膨胀率变化的幅度最大；掺砂比例为40%时,荷载的增加对抑制膨胀性效果最明显；掺砂比例对无荷膨胀率影响很小,基本呈平缓线性变化。通过对掺砂效果的综合比较,掺砂10%能最快最经济抑制膨胀。

Expansive Properties of Expansive Soil Improved by Mixing Weathered Sand

This research is carried out to improve the expansive soil subgrade of the first-class highway from Xiaoxita to Yaqueling in Yichang city. Different amounts of weathered sand were mixed in expansive soil samples to investigate the expansive soil’s free swelling ratio, unloaded swelling ratio, loaded swelling ratio (25kPa and 50kPa) and expansion force. Through heavy compaction test and comparison of swelling rates, it’s found that adding weathered sand changes the water content and compaction of expansive soil, and hence restrains the expansion. The free swelling ratio of expansive soil mixed with weathered sand is less than 35%, which meets the requirement of subgrade construction. Different ratio of mixed sand to soil has different effect on the expansion when the mix ratio is 10%, the free swelling ratio and expansion force decrease most remarkably; when the ratio is 40%-50%, the swelling rate under 25kPa loading changes most evidently; when the ratio is 30%-40%, the swelling rate under 50kPa changes by a biggest margin; when the ratio is 40%, the increase of load can well control the expansion. The amount of weathered sand has slight influence on unloaded swelling ratio. It’s concluded that the expansion of expansive soil mixed with 10% weathered sand could be restrained most rapidly and economically.