活性MgO-粉煤灰固化黄土剪切特性试验研究

黄土固化处理是解决黄土地区建筑地基变形与沉降问题的有效途径。选取活性MgO、粉煤灰和水泥3种不同类型固化剂,通过开展不固结不排水直接剪切试验,研究固化剂掺量、类型和养护龄期等因素对黄土剪切性能的影响。结果表明:活性MgO可显著提高黄土抗剪强度;随着活性MgO掺量和养护龄期增加,固化黄土黏聚力和内摩擦角先增加后减小,在6%掺量和14 d养护龄期附近达到峰值;粉煤灰掺入可有效改善活性MgO固化黄土抗剪性能,尤其对黏聚力提高效果明显,随着养护龄期和固化剂掺量增加,固化土抗剪强度不断增大;水泥固化黄土抗剪强度随水泥掺量和养护龄期呈现类似增长规律。活性MgO-粉煤灰等3种材料可提高固化黄土抗剪强度,MgO-粉煤灰效果最优,单掺活性MgO次之,二者均优于水泥。

Experimental Investigation on Shear Properties of Reactive MgO-fly Ash Stabilized Loess

Loess stabilization is an effective approach to solve the deformation and subsidence problems of structural foundations in loess area. Direct shear tests under undrained-unconsolidated condition were conducted to evaluate the shear strength of loess specimens modified with various contents of reactive MgO, fly ash and cement under 7, 14 and 28-day curing conditions. Test results demonstrate that the shear strength of reactive MgO-stabilized loess samples is significantly enhanced. As reactive MgO amount and curing time increasing, the cohesion as well as internal friction angle initially rises up to the peak value at 6% MgO content and 14-day period, following by an important reduction process. Furthermore, the added fly ash exerts a considerable promotion on shear properties, especially on the cohesion of reactive MgO solidified loess. The shear strength of samples stabilized with reactive MgO and fly ash binders rises continually with the growth of curing age and additive amount. The same incremental tendency attached to the increase of curing time and binder content is also detected in shear strength evolution of cement-treated specimens. In terms of developing the shear performance of loess, reactive MgO-fly ash binder outperforms reactive MgO that as well surpasses the traditional binder cement.