非饱和土砂土湿吸力

为了研究非饱和砂土湿吸力的影响因素及变化规律,利用非饱和砂土作为挡土墙的填土,通过观测填土的临界深度,应用朗肯主动土压力理论求其似粘聚力,根据似粘聚力来研究非饱和砂土颗粒间湿吸力的变化规律。研究结果表明:非饱和砂土的湿吸力是随着含水量的增大而增大,且开始阶段速率变化大;当非饱和砂土具有湿吸力时,存在一个临界含水量和临界粒径;在含水量相同条件下,相同粒径磨圆愈好湿吸力愈大。该研究方法操作简单、新颖,其结论可为非饱和土的研究提供参考。     

砂性地层中盾构隧道掘进围岩变形特性

以狮子洋隧道砂性地层段地质条件和施工资料为基础,建立有限差分数值计算模型.通过比较不同断面监测点随开挖进程的位移值,结果表明:先掘隧道围岩向中心收缩,上下部围岩变形明显大于两侧;后掘隧道对先掘隧道有横向外挤的作用,但对纵向几乎没有影响.对有、无渗流作用的2种工况的比较分析说明,起初渗流对围岩变形影响不大,但最终加剧了围岩的变形程度.提出了开挖面前方土体扰动的累积效应和累积效应曲线的确定方法,通过该曲线可确定土体扰动范围和程度,经过理论分析,认为影响土体位移速率的2个因素是土体与开挖面间距和盾构推力.     

砂砾岩储层孔隙结构复杂模态差异机制

针对砂砾岩储层孔隙结构复杂、模态成因机制不明的情况，以325块岩芯分析化验数据为基础，利用压汞、铸体薄片、扫描电镜及X射线-CT扫描等方法，开展了岩石相分类、孔隙结构模态和驱油效率差异机制的研究，从油田开发与实用相结合的方式考虑，将砂砾岩储层岩相分为3大类、7亚类、13细类。研究表明：不同孔隙结构模态特征及注水驱替效率差异较大。单模态岩石颗粒以粗砂岩为主，孔隙发育程度高，孔隙呈网络状结构，相互连通性较好，注水驱替模式以网络状连通驱替为主，效率较高。双模态岩石颗粒由砾岩和中-粗砂岩两级颗粒组成，孔隙较发育，孔隙呈疏网状结构，相互连通性一般，注水驱替模式以星点状连通驱替为主，效率一般。复模态岩石颗粒由砾石、中-粗砂岩、粉砂或泥质三级颗粒组成，孔隙发育一般，孔隙呈星点状结构，相互连通较差，注水驱替模式以零星散乱状驱替为主，局部存在高渗带，效率整体较差。相同岩相呈不同孔隙结构模态和不同的岩相呈相同的结构模态的情况普遍存在。颗粒排列方式及成岩作用差异改造导致了同相异态，而颗粒分选、磨圆、排列方式等因素形成了异相同态。     

Across-shore distribution of Ocypode quadrata burrows in relation to beach features and human disturbance

Spatial distribution patterns of the ghost crab Ocypode quadrata were analysed using different approaches at one disturbed and two preserved reflective sandy beaches of the Mexican Caribbean. We used spatial correlation analysis to describe the across-shore distribution of O. quadrata and their patch dynamics by beach and sampling time. In addition, we analysed the across-shore variability of habitat extent of O. quadrata (habitat envelope) and its relation to human disturbance and beach features. The spatial structure of burrow density was consistent through time, showing a bimodal distribution with very low abundance in the mid distribution range and a discrete increment of burrows to landward. Nonetheless, the size of patches varied temporally for the three beaches. Burrow size increased from seaward to landward. The location of the first burrow and the habitat envelope varied among sampling times and beaches. The location of the first burrow is mostly mediated by the swash climate, while the habitat envelope is mainly controlled by the level of human disturbance. Despite the low number of disturbed and control beaches, our results suggest that the habitat envelope could be included in future studies when using ghost crabs as indicators of human disturbance. Polynomial models and variographic analysis proved to be useful tools to describe the across-shore distribution and patch dynamics of the ghost crab.     

Along‐ and across‐shore components of the spatial distribution of the clam Tivela mactroides (Born, 1778) (Bivalvia,Veneridae)

Beach clam fisheries often provide an alternate income for traditional fishermen, but this activity is highly vulnerable to urbanization of coastal areas. Tivela mactroides is a beach clam commonly harvested in the Caribbean (Venezuela) and on the south‐eastern Brazilian coast. Only localized records on its spatial structure in size and abundance are available to support management of this clam. The present study showed that the spatial distribution in abundance and size of T. mactroides in Caraguatatuba Bay, state of São Paulo, Brazil, has both along‐ and across‐shore (intertidal and subtidal) components. The nature of this distribution should be taken into account in the design of further population or monitoring studies concerning this species. Clam density varied along‐shore, with a tendency towards higher numbers of individuals in the stations near the northern side of river mouths of this bay. Lower densities were related to the occurrence of sea‐stars and sand‐dollars. The intertidal and subtidal across‐shore distribution of clam abundance and size varied between and within areas (southern and northern). The individuals from the southern area were concentrated at intermediate tidal levels (0.2–0.6 m in relation to mean low water), whereas in the northern area the clams were more homogeneously distributed. The uppermost limit of their distribution was 0.8 m (southern) and 0.4 m (northern), and an upwards tendency towards increased size was more evident in the northern area. In the subtidal, abundance and individual size tended to increase from the deepest (4.5 m) to the shallowest (0.5 m) levels only in the southern area. Individual clams in the northern area tended to be smaller and more abundant than in the southern area. The species had an ontogenic distribution: small‐sized individuals were recorded only in the subtidal. Possible causes for these patterns and for the differences between areas (human exploitation, organic pollution, beach morphodynamics, differential recruitment, and adult–larvae interactions) are discussed, and specific studies are suggested to evaluate formally the proposed hypotheses.     

单一沙坝型海滩平衡剖面形态预测公式

基于戴河口至洋河口海滩养护后的海滩平衡剖面实测资料,以存在离岸单一沙坝的低能砂质海滩为研究对象,分析其海滩剖面形态演变,提出以背景剖面和沙坝剖面叠加的单一沙坝型海滩平衡剖面预测公式。背景剖面基于最大信息熵原理充分考虑沙坝向岸侧和离岸侧差异,沙坝剖面则采用3～4个参数以抛物线函数形式分段描述非对称性沙坝形态。该平衡剖面公式对戴河口至洋河口岸段养护后的海滩剖面拟合效果较好,且成功应用于北戴河老虎石海滩和美国佛罗里达Fort Myers海滩,能较准确反映存在离岸单一沙坝低能海滩的平衡剖面特性。     

黄陵地区延长组长6段深水砂岩储层特征分析

以鄂尔多斯盆地黄陵地区延长组长₆段为研究对象,基于区内丰富的钻井取芯、测录井及分析化验资料,对长₆段深水砂岩特征及不同砂体类型储层之间的差异性进行了分析。结果表明,根据砂体形成机制及其构造特征的不同,研究区砂体类型可划分为砂质碎屑流砂体、砂质滑塌砂体及浊流砂体3大类。其中,砂质碎屑流砂体的石英、长石含量及结构成熟度相对较高,储集空间以长石溶孔和残余粒间孔为主,储层物性也明显优于其他两类砂体。进一步分析发现,由于结构成熟度和矿物含量的差异,砂质碎屑流砂体成岩早期抗压实压溶作用更强,中晚期易溶矿物溶蚀增孔、构造破裂增缝等建设性成岩作用也较为强烈,从而决定了砂质碎屑流砂体是研究区最有利的储集岩体。     

杨树叶生物质炭对风沙土中氮形态分布的影响

将杨树叶生物质炭添加到模拟施肥的风沙土中, 研究杨树叶生物质炭对风沙土中氮形态分布的影响. 结果表明： 与传统施肥模式及测土配方施肥模式相比, 制备的生物质炭可增加风沙土铵态氮、 硝态氮、 速效氮和全氮的质量比; 在玉米的生长周期内, 铵态氮、 硝态氮和全氮质量比与生物质炭的添加量成正比; 当生物质炭添加质量分数为2%时, 与土壤充分混合, 铵态氮、 硝态氮和全氮的质量比分别为36.43 mg/kg,35.02 mg/kg,5.76 g/kg, 传统施肥模式下的质量比最高; 速效氮在添加生物质炭的质量分数为0.5%时, 测土配方施肥模式下的质量比最高, 为79.52 mg/kg.     

油蒿(Artemisia ordosica)对半干旱区沙地生境的适应及其生态作用

我国温带半干旱区沙地生境的主要特征是干旱少雨、沙源丰富和大风频繁,这种特定条件进化出我国特有的优良固沙植物--油蒿.在长期的进化过程中,油蒿形成了独特的形态结构、生理特征和繁殖习性,能够很好地适应沙地环境.油蒿群落不仅能够防风固沙,影响沙地生态系统的水分运移与分配,还能促进土壤的发育.因此,油蒿在适应沙地生境的同时对沙地产生巨大的影响和改造作用.油蒿群落对沙地生境的不断改造,推动了植物群落的演替,最终使流动沙丘转变为丰茂的植被.     

全-强风化砂质板岩填料性能及其改良试验

对全-强风化砂质板岩进行了室内土工试验,分析其击实参数、级配组成与液塑限值,判定原状土是否适用于高速公路路基的填筑;研究了水泥改良剂的主要性能指标,给出了水泥改良全-强风化砂质板岩的液塑性指标随掺灰量的变化趋势;通过直剪试验,考察掺灰量与侧限养护条件对水泥改良全-强风化砂质板岩剪切强度的影响.