污水浸泡对水泥土强度和电阻率特性影响的试验研究

为了揭示污水对水泥土的影响规律,并尝试采用电阻率法作为描述强度和污染特征的手段,把粉质黏土和两种水泥（普通硅酸盐水泥、矿渣硅酸盐水泥）制作的水泥土试块分别浸泡在3种液体（自来水、生活污水、造纸厂污水）中模拟环境侵蚀。首先对比分析了污水对土体液塑限的影响,其次研究了龄期、水泥类型、污水类型等对水泥土抗压强度和电阻率的影响,考察了电阻率和抗压强度的关系。结果表明：污染后土样的液限、塑限均增大,塑性指数减小;水泥土抗压强度和电阻率均随龄期增加而增长;污水均降低了水泥土的抗压强度和电阻率,但是矿渣硅酸盐水泥土的抗压强度和电阻率均高于普通硅酸盐水泥土,说明在污水环境中,矿渣水泥对水泥土有一定的抗劣化能力;在不同的龄期、水泥类型、污水类型下,水泥土电阻率均与抗压强度呈现出一致的变化规律,二者线性相关。     

移动状态边界面法在黏性土不排水蠕变孔压分析中的应用

在黏性土的各种流变现象的数学模拟研究中,不排水蠕变孔压方程几乎是空白。基于临界状态土力学理论,采用与时间相关的移动状态边界面法,给出了适用于正常固结黏性土的不依赖状态边界面具体形态的不排水蠕变孔压公式。正常固结黏性土的不排水蠕变孔压可以看作是体积蠕变势和剪应力水平增大造成的剪缩这两种作用的结果,前者与参数 有关（ 为次压缩指数, 为压缩指数）,后者则与状态边界面的具体形态有关。在此基础上进一步给出了可方便用于试验数据分析的双对数和单对数形式的两个公式。以修正剑桥模型椭圆形状态边界面为例,分析了双对数和单对数坐标系下蠕变孔压曲线的斜率m和m′与土的流变参数 的关系。采用提出的方法,很好地预测了Walkers给出的Leda clay黏土的蠕变孔压系数,并基于以上两种作用解释了Leda clay黏土的蠕变孔压形成的机制。     

干旱区膜下滴灌棉田表层土壤盐分日内动态特征

利用便携式土壤盐分计测量膜下滴灌棉田不同位置和不同深度的土壤电导率,来研究膜下滴灌条件下表层土壤电导率的日内变化特征.结果显示:干旱区一膜两管膜下滴灌条件下,窄行处土壤电导率值最低,膜间最大,宽行居中,表层土壤电导率值存在显著的日内变化特征,早晚土壤电导率值低,中午电导率值高,上午的上升速率大于下午的下降速率;窄行处相对变化幅度大,膜间绝对变化幅度大,土壤电导率值日内变化幅度随深度呈减小趋势;膜下滴灌情况下,表层土壤电导率值的变化受土壤温度和气温的影响显著,但二者相关性复杂,不同深度、不同时间段的相关性不同,膜间大多呈显著正相关,窄行大多呈非显著正相关,宽行处上午呈非显著正相关,但下午呈显著负相关.     

Monitoring over‐winter soil water dynamics in a freezing and snow‐covered environment using a thermally insulated tensiometer

Water potential below a frozen soil layer was continuously monitored over an entire winter period (using thermally insulated tensiometers sheltered in a heated chamber) along with other soil, snow and atmospheric variables. In early winter, the freezing front advanced under a thin snow cover, inducing upward soil water flow in the underlying unfrozen soil. The freezing front started to retreat when the snow cover became thick enough to insulate the soil, resulting in the reversal of the flow direction in the unfrozen zone. These data provide a clear illustration of soil water dynamics, which have rarely been monitored with a tensiometer. Copyright © 2005 John Wiley & Sons, Ltd.     

新型抗滑结构围桩-土的耦合效应分析

在引入围桩-土耦合式抗滑结构的基础上建立数值分析模型;通过分析该抗滑结构中围桩-土的应力、应变分布规律,详细探讨围桩-土整个结构的耦合效应特征。进一步开展模型试验,测试并分析围桩前、后土压力和桩身弯矩分布特征,论证了围桩-土耦合式抗滑结构的作用机制。最后,分析了桩后距离、不同深度及不同土体强度参数对土拱效应的影响。得到：（1）围桩与桩内土体耦合呈现出4种应力拱形态：紧邻围桩后为扩肩型拱、围桩间双曲线型拱、围桩间凸向桩外的抛物线型拱、围桩间凸向桩内的抛物线型拱;（2）相邻围桩采用约4倍桩径间距、正六边形布置并顶部用圈梁固结、锚固一定深度可形成一种耦合式抗滑结构。该结论对于该新型抗滑结构的推广应用具有一定的指导意义。     

Evidence for pervasive mud volcanism in Acidalia Planitia, Mars

We have mapped 18,000+ circular mounds in a portion of southern Acidalia Planitia using their sizes, shapes, and responses in Nighttime IR. We estimate that 40,000+ of these features could occur in the area, with a distribution generally corresponding to the southern half of the proposed Acidalia impact basin. The mounds have average diameters of about 1 km and relief up to 180 m and most overlie units mapped as Early Amazonian.High resolution images of mound surfaces show relatively smooth veneers, apron-like extensions onto the plains, moats, and concentric circular crestal structures. Some images show lobate and flow-like features associated with the mounds. Albedo of the mounds is generally higher than that of the surrounding plains. Visible and near-infrared spectra suggest that the mounds and plains have subtle mineralogical differences, with the mounds having enhanced coatings or possibly greater quantities of crystalline ferric oxides.Multiple analogs for these structures were assessed in light of new orbital data and regional mapping. Mud volcanism is the closest terrestrial analogy, though the process in Acidalia would have had distinctly martian attributes. This interpretation is supported by the geologic setting of the Acidalia which sits at the distal end of the Chryse-Acidalia embayment into which large quantities of sediments were deposited through the Hesperian outflow channels. In its distal position, Acidalia would have been a depocenter for accumulation of mud and fluids from outflow sedimentation.Thus, the profusion of mounds in Acidalia is likely to be a consequence of this basin’s unique geologic setting. Basinwide mud eruption may be attributable to overpressure (developed in response to rapid outflow deposition) perhaps aided by regional triggers for fluid expulsion related to events such as tectonic or hydrothermal pulses, destabilization of clathrates, or sublimation of a frozen body of water. Significant release of gas may have been involved, and the extensive mud volcanism could have created long-lived conduits for upwelling groundwaters, providing potential habitats for an in situ microbiota.Mud volcanism transports minimally-altered materials from depth to the surface, and mud volcanoes in Acidalia, therefore, could provide access to samples from deep zones that would otherwise be inaccessible. Since the distal setting of Acidalia also would favor concentration and preservation of potentially-present organic materials, samples brought to the surface by mud volcanism could include biosignatures of possible past or even present life. Accordingly, the mounds of Acidalia may offer a new class of exploration target.     

土工格栅加筋膨胀土渠坡数值模拟研究

对土工格栅加筋膨胀土渠坡这种较新的膨胀土处理措施进行研究,在考虑土工格栅与填土之间的相互作用、膨胀土吸水膨胀、软化特性等膨胀土渠坡关键影响因素的基础上,提出了土工格栅加筋膨胀土渠坡数值计算的新思路,并采用有限差分软件Flac3D进行了验证。数值算例结果表明,土工格栅对膨胀土渠坡有明显的水平位移约束作用,是有效的处理措施,可以在实际工程中采用。     

Species Composition and Some Ecological Notes on Diatom Communities of a Lotic Environment in Tarhunãh,Libya Artenzusammensetzung und einige ökologische Notizen über Diatomeengesellschaften eines lotischen Biotops in Tarhunãh/Libyen

Libya occupies a large part of the Sahara Desert, and is a predominantly arid country with extremely scarce freshwaters. Despite aridity, a distinct higher rainfall zone exists along its mediterranean coastal belt. A lotic environment (perennial stream) in Ain-Scersciara, Tarhunãh in northwest Libya was studied for the species composition of diatom communities and their ecological characteristics. The waters are generally alkaline (pH = 7.5) and of hard-water (conductivity = 2008 μS/cm) type. The epiphytic diatom growth on benthic filamentous algae was high (32 taxa) with Amphora veneta as a very common taxon. Gomphonema parvulum var. micropus was an important taxon found in scrapings from the leaves of macrophytes and stony substratum. Nitzschia and Navicula showed high species richness (9 taxa in each) followed by Gomphonema (6 taxa). The ecological attributes of the majority of taxa show an oligohalobe status and alkaliphilous indicator.     

硅灰加固宁波软土的试验研究

为探索硅灰对软土的力学性质的影响,以宁波鄞州地区一种淤泥质黏土为试样,掺入不同量的硅灰,对硅灰加固土的力学性质和结构特征进行了测试。采用三轴不固结不排水剪切试验,测试分析了不同掺入量的硅灰加固土的应力应变关系,通过扫描电镜SEM照片分析了不同硅灰掺入量的硅灰加固土的结构特征。结果表明:(1)硅灰可以提高软土的黏聚力,黏聚力随着硅灰掺入量的增加而增大;(2)随着硅灰掺入量的增加,硅灰加固土的抗变形能力呈先增加后减小的趋势;(3)同一围压条件下,随着硅灰掺入量的增加,硅灰加固土的破坏偏应力逐渐增加;(4)随着硅灰掺入量的增加,硅灰加固土中大孔隙逐渐减少,小孔隙逐渐数量增加,孔径<1μm的小孔隙组分逐渐占优。     

某金矿区农田土壤重金属元素Pb的累积速率

以某金矿区农田土壤重金属Pb为研究对象,分别以2004和2012年采集样品的测试结果作为计算农田土壤重金属Pb累积速率的依据,以2004—2012年作为计算时间区间,以农田土壤重金属Pb的累积速率为研究内容,采用对比分析方法,分析区域Pb的累积速率特征,阐明人类工程活动极大地影响着农田土壤重金属Pb的累积过程。研究结果表明,全区农田土壤Pb平均累积速率为31.8mg/kg·a-1。选取选矿厂、冶炼厂、尾矿库、污水灌溉区、车载尾矿弃渣等典型污染源,对周边农田土壤Pb累积的时空变化特征进行分析。结果显示,选矿厂对农田土壤Pb累积的影响最大,其周边农田土壤Pb累积速率相当于全区Pb累积速率的4倍,该结论对防治重金属污染及保障人体健康具有实际指导意义。