摘要
由于长期遭受卸荷和化学风化作用 ,特别是亚热带风化淋滤作用 ,下第三系泥岩或砂质泥岩的残积层不仅发生粘土矿物转化 ,而且造成密度的强烈降低。百色盆地膨胀土具有残积型膨胀土所特有的低容重 (约 19.0 2kN/m3)、高孔隙比 (0 .75～ 1.78)、高含水率 (2 5 %～ 41% )、高分散性 (<2 μm含量 >5 0 % )、强收缩 (体缩 >15 % )等一系列不良工程性质。这种膨胀土无侧限单轴抗压强度仅 0 .0 3～ 0 .42MPa左右 ,不属于膨胀岩范畴。扫描电子显微镜 (SEM )和X -射线衍射 (XRD)鉴定结果表明 ,其主要粘土矿物成分为I/S混层矿物 ,而不是伊利石 (有别于前人的认识 )。现行规范中膨胀势判别方法的缺陷造成设计安全系数偏低 ,是路基严重变形、破坏的重要原因之一。
Suffering long from unloading and chemical weathering processes—especially the subtropical eluviation, not only clay mineral species transformation but also density decrease have taken place in eluvium of early Tertiary mudstone or sandy mudstone. Baise Basin (Guangxi municipality) swelling soil has a series of bad engineering properties such as low unit weight (about 19.02 kN/m 3), high void ratio (0.75～ 1.78 ), high water content (25%～41%),and high dispersibility (<2 μm grain>50%),and high contractility (bulk shrinkage>15%) which are typical characteristics of eluvial expansive soils. The unconfined compressive strength of this kind of soil is only 0.03～0.42 MPa, so it should not be categorized as “expansive rocks'. The test results of scanning electronical microscope (SEM) and X ray diffraction (XRD) indicate that the main clay mineral is I/S (illite/montmorillonite) mixed layer mineral but not illite (different from existing opinions). Low safety factor resulted from defects in the discriminance of expansive potential, which is stipulated in the active official criterion. And this is one of the important causes of serious deformation and damage of roadbed. Engineering measures to deal with these roadbed defects are suggested in this paper.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2001年第4期463-467,共5页
Chinese Journal of Geotechnical Engineering
基金
国家自然科学基金资助项目 (49872 0 86 )
关键词
路堤
膨胀土
路基病害
南昆铁路
Nankun railway
expansive soils
roadbed
defects,engineering measures
