Understanding the effect of a static driving shear stress on the liquefaction resistance of medium dense granular soils

The influence of a driving static shear stress on the liquefaction resistance of medium dense granular soils is investigated. A laboratory study of the behavior of five sands (percentage of silt varying between 2 and 42%, and D₅₀ varying between 0.55 and 0.09 mm) was undertaken. These five sands were sampled from the foundations of two dams in Quebec (Canada). Sixty cyclic direct simple shear (DSS) tests were performed with and without a driving static shear stress. Relative densities D_r varied between 60 and 70%, and static shear stress ratios =τ_st/σ′_vc varied between 0.2 and 0.6. The presence of static shear stress increased the cyclic strength of these soils. A relation between and K() factor giving the effect of preshearing on cyclic shear resistance is obtained. The mechanical competence is examined as a function of D₅₀ and percentage of fines. The observed dilatancy yielded rather cyclic mobility than liquefaction.     

A concise parameterization of the hydraulic conductivity of unsaturated soils

The parameter n in the well-known expression for hydraulic conductivity K=K₀S_eⁿ (where K₀ is its value at satiation and S_e the effective saturation) is determined as a function of the exponent in the power form of the soil–water retention relationship. The result is validated with an extensive experimental database comprising some 43 soils, collected by Mualem.     

ROCESSES OF EPHEMERAL GULLY EROSION

IINTRoDUCTIONEphemeralgulliesaresmallerosionalchannelsonagriculturalIandscapescausedbytheconcentrationofoverlandflowtypicallybetweentwoopposingslopes(ahollow),oftenformedduringasingIerainfaIlevent.Sincethescouredsoilvolumeisnotverylargewithinthesegullies,farmerscaneasilyrefillthem.Ingeneral,ephemeralgulliescanreappearatornearthesamelocationonayearlybasisbecausethesurfacetopograPhyofthefielddoesnotchangeappreciably.Mostephemeralgulliesoccuroncultivatedfieldswithhighlyerodiblesoils,withlit…     

利用断层气(土气氡)探测琼北地区的断裂活动性

对琼北地区的ＮＥＥ、ＮＷ向两组断裂及历史强震区进行跨断层土氡测量,以探明该区断裂的近期活动性。结果表明：⑴ＮＥＥ向的王五－文教断裂、ＮＷ向的铺前－清澜断裂现今都有较强的活动性,铺前－马袅断裂、临高断裂和长流－仙沟断裂也有一定的活动性;⑵就断裂活动的总体水平而言,琼东北地区较之西北地区高,而琼东北地区的南部又较北部高。     

砂土液化判定评价与对策

砂土液化的评定、评价及对策虽然要概念不同,但有着必然的联系,本文通过工程实例分析,对液化判定、评价及对策进行较为详细的阐述。     

GIS环境中砂土液化评价方法

本文介绍了一种适用于ＧＩＳ环境下分析液化可能性指标的砂土液化分析方法,详细阐述了分析过程和它与ＧＩＳ的接口情况。     

抗液化排水井(桩)间距确定方法的研究

运用土力学、土动力学以及地下水向集水建筑物运移的非稳定流理论等的有关原理,提出了一种确定防止饱和砂土液化排水井（桩）间距的计算方法,并通过试验对这一方法进行了验证。     

陕北榆神府矿区地质环境现状及采煤效应影响预测

以我国西部特大型煤田榆神府矿区为例 ,从环境工程地质学角度分析了该区煤炭资源开发中主要的环境工程地质问题 ,并进行了综合地质环境质量现状和采后变化预测评价。研究结果对该区煤炭资源合理开发宏观决策和规划设计有直接指导意义。     

砂土地震液化的改进进货遗传算法判别

改进了进化遗传算法,提出了新的交叉算子和变异算子,使之具有更好的全局收敛能力。砂土液化是一种危害极大的地震破坏现象,其影响因素很多,选择地震烈度、砂土粒径、相对密度、标贯击数和有效正应力为判据,利用改进了的进化遗传算法建立了砂土地震液化的判别模型。与液化情况比较表明,改进进化遗传算法应用于砂土地震液化的判别效果良好。