Soil wettability in ground engineering: fundamentals,methods, and applications

Wettability is a fundamental property controlling the extent of wetting in flat and granular solids. In natural soils, wettability affects a wide variety of processes including infiltration, preferential flow and surface runoff. In mineral processing, wettability is paramount in enhancing the efficiency of separation of minerals from gangue. The manipulation of surface wettability is equally crucial in many industrial applications. For instance, superhydrophobic surfaces are those on which water drops roll off easily and as such are used for self-cleaning applications. Therefore, while wettability is strongly cross-disciplinary, its evolution has been discipline-specific with a direct extrapolation or transfer of concepts, approaches, and methods to ground engineering unlikely to remain valid. This paper synthesizes relevant aspects from surface chemistry, materials science, mining engineering, and soil science, and discusses their implications within the context of new granular materials that resist wetting, for use in barriers or ground improvement and, in unsaturated soils, where the effects of wettability have been documented.     

Double pot cover effect in unsaturated soils

The phenomenon of moisture increase under an impervious cover in soils due to thermal gradients is defined as the pot cover effect, which may lead to an obvious soil moisture increase in the shallow soil. This paper explores a measure of laying an impervious layer at an appropriate depth in the process of foundation treatment to eliminate the potential moisture increase in the covered soil. Because the impervious cover above the soil and the impervious layer inside the soil constitute a “double pot cover” structure, the moisture migration in the covered soil with an impervious layer is generalized as the double pot cover effect. To investigate the mechanism of the double pot cover effect and further determine the optimal depth of the impervious layer, a numerical model is established to simulate this problem. Analysis results indicate that the moisture increase under the cover varies with the depth of the impervious layer. As the impervious layer is laid at a certain depth, the moisture increase reaches a minimum value. Moreover, the double pot cover effect under different boundary temperatures is further discussed. Results show that the moisture increase in the covered soil can be significantly reduced by laying the impervious layer slightly below the freezing front (0 °C).

     

广东三洲矿田构造序列研究及其意义

三洲矿田内主要矿床与燕山期更晚的构造活动腾。燕山期构造活动可分为六个序列：（１）下石炭统与上三叠统不整合面附近和不整合面之上的上三叠统一下侏罗统中的低角度正滑断层及伴生构造,２）泥盆系－石炭及上三叠统一下侏罗统中的纵弯０褶皱北西向逆冲支,４）北东向平移断层,５）第二次北西向逆冲断层,６）伸展性正滑小断层。其中１、４、５三个构造序列是主要控矿构造,第１构造序列控制了长坑金银矿,第４构造序列控制蛘     

焦坪矿区侏罗纪煤层地面煤层气井压裂液优选实验

压裂液与储层的配伍性是影响水力压裂效果的关键因素之一。为了研究适合焦坪矿区侏罗纪煤层地面煤层气井使用的压裂液配方,通过分析储层特征,提出了相适应的压裂液配方,并借助室内模拟实验对压裂液配方进行优选评价。结果表明：活性水压裂液配方中防膨剂优选1.0%氯化钾防膨效果较好;活性水压裂液配方中助排剂优选0.05%氟炭离子表面活性剂或注入乙醇段塞,再注压裂液这两种助排剂效果较好;对于生物酶破胶压裂液配方建议进一步进行现场试验。     

多年冻土区活动层冻融状况及土壤水分运移特征

利用位于典型多年冻土区的唐古拉综合观测场2007年9月1日—2008年9月1日实测活动层剖面土壤温度和水分数据,对多年冻土区活动层的冻结融化规律进行研究;同时,对冻融过程中的活动层土壤液态水含量的变化特征进行分析,探讨了活动层内部土壤水分分布特征及其运移特点对活动层冻结融化过程的影响. 结果表明：活动层融化过程从表层开始向下层土壤发展,冻结过程则会出现双向冻结现象. 一个完整的年冻融循环中活动层冻结过程耗时要远远小于融化过程. 活动层土壤经过一个冻融循环,土壤水分整体呈现下移的趋势,土壤水分逐步运移至多年冻土上限附近积累. 同时,土壤水分含量和运移特征会对活动层冻融过程产生显著的影响.     

中国北方三流域河流—沙漠过渡带地表沉积物化学元素空间差异分析

通过对克里雅河、毛布拉格孔兑以及西拉木伦河三流域的河流-沙漠过渡带地表沉积物的7种常量氧化物以及15种微量元素进行因子分析,结果显示:三个流域之间或不同河段因子分析提取的公因子均可以概括为较稳定的铁锰矿物、较不稳定的长石类和方解石（白云石）类等硅酸盐矿物以及稳定的稀土元素和重矿物等类别;河流间因子分析结果表明,自西向东三个流域沿河地表沉积物的化学元素富集与迁移程度呈递增趋势,化学风化程度增强;流域内因子分析结果表明,自上游至下游,样点化学组成均愈变复杂,不同河段或不同河岸沉积物化学元素空间分布规律与其物源、地貌格局以及水分条件等因素有关;自河床至阶地,不同地貌单元地表沉积物化学元素呈相异的递变规律,这与在距离河道远近不同,物源、动力因素的分配不同有关。