考虑压实度差异的软岩路堤填料强度与变形特性试验研究

路堤填筑碾压施工平面上不同部位填料所受约束条件存在较大差异,特别对于颗粒强度较低、骨架结构锁固效应较弱的软岩填料,碾压后靠近路堤中部的填料压实度大于两侧。基于采用含砂质泥岩作为填筑料的某路堤工程开展试验研究,结果表明:①靠近路堤中线和两侧临空面填料现场检测压实度分别不低于0.95和0.93,满足下路堤压实度要求,但压实度存在差异;②对碾压后的路堤填料取样,并分别在0.95和0.93的压实度下进行大型三轴固结排水试验,压实度0.95试样摩擦角较压实度0.93的约高13%,但黏聚力基本相同;③大应变过程压实度0.93填料体变与围压基本无关,细观结构压缩呈主导,而在压实度0.95下体缩与围压呈正相关,颗粒骨架受力更为充分,但仍呈全过程体缩,表明大变形过程伴随有颗粒破碎后的二次挤密;④进一步分析发现两种压实度下球应力-体变以及体积模量-围压均很好满足线性拟合关系,采用邓肯-张E-B模型可较好描述压实度差异状态下软岩填料的变形力学特性。

Experimental Study on Strength and Deformation Properties of Soft-rock Filling Embankment Considering Compaction Difference

The constraint conditions of filler on construction plane of embankment filling vary remarkably for each part. In particular, the compaction of soft-rock filler with low particle strength and weak structural lock effect is higher close to the center than that close to both sides. We carried out experimental study on an embankment project with sandy mudstone filler, and the results manifested that: 1) the measured compaction degrees of filler close to the center and both sides are not lower than 0.95 and 0.93, respectively, which meets the compaction requirements of embankment for second class highway, yet still with some difference; 2) large-scale triaxial consolidated-drained test was conducted on the rolled filler collected on site at the compaction degree of 0.95 and 0.93, respectively, and the results revealed stable cohesion and larger friction angle of sample at 0.95 compaction degree than that at 0.93 compaction degree by 13%; 3) in large strain process, the volumetric strain was generally irrelevant with confine pressure at the compaction degree of 0.93, dominated by mesostructure compression, while at the compaction degree of 0.95, volumetric shrinkage was positively correlated with confining pressure despite more sufficient stress in particle skeleton, implying that the large strain process was accompanied by secondary compaction after particles breakage; 4) at both compaction degrees, the relations of spheric stress versus volumetric strain and volumetric modulus versus confining pressure both obey linear fitting relation. Duncan-Chang E-B model could well describe the deformation mechanical characteristics of soft rock filler under different compaction degrees.