控制UCS条件下的路基无机结合料改良土动力性能评价

Dynamic Performance Evaluation of Inorganic Binder Stabilized Subgrade Soil under UCS Control

针对湖南省四种不同塑性指数(PI)的路基软土,在控制无侧限抗压强度(UCS)为350 k Pa和700k Pa的条件下,研究了采用粉煤灰、石灰、水泥三种无机结合料进行改良的配比组合方案,并对改良土进行了循环加载试验以评价其动力性能(如回弹模量和累积塑性应变)。研究结果表明,各种结合料组合对提高USC的效果排名为:(石灰+水泥)>水泥>(石灰+粉煤灰)>粉煤灰>石灰,为达到目标UCS,土的塑性指数越大,则改良所需的结合料组合排名越靠前。由于素土类型和改良方案的区别,UCS相近的改良土可能呈现较大差异的回弹模量。在同一UCS控制条件下,改良土回弹模量总体随着水/结合料比例的减小而提高,而累积塑性应变则总体随着该比例的减小而降低,回弹模量、累积塑性应变均与土的PI无明显相关性,在7 d的基础上适当延长养护时间可以有效提高回弹模量,在实际工程中,利用改良土应重视压实后的养护工作。

This paper presents laboratory tests on four typical weak subgrade soils with different plastic index（PI） in Hunan Province. At first,in order to achieve the target unconfined compression strength（UCS） of 350 k Pa and 700 k Pa,proportioning scheme of stabilizer consisting of fly ash,lime and cement used for stabilization was studied. Afterward the corresponding dynamic performance related properties（e. g.,the resilient modulus and accumulative plastic strain） was evaluated by repeated loading tests. The results show that the effect rank of inorganic binding material combination on enhancing UCS is：（lime ＋ cement） cement （lime ＋ fly ash） fly ash lime. To achieve the target UCS,higher rank combination is needed for soil with higher PI. In virtue of raw soil and stabilization scheme distinction,stabilized soils with similar UCS may present relatively large difference in resilient modulus.With the same UCS,resilient modulus totally increases with the decrease of water/stabilizer content ratio,while accumulative plastic strain reduces with the ratio decrease. There is no obvious correlation between PI and resilient modulus as well as accumulative plastic strain. Appropriately prolonging curing time based on seven days can effectively improve resilient modulus. Therefore,curing work of stabilized soil after compaction should be paid enough attention in actual engineering.