Characterization and constitutive modeling of red clay contaminated with ammonium carbonate

Conventionally, red clay is used for agricultural purposes in southern China. Fertilizers, especially urea, are commonly introduced into the red clay to improve the crop yields. However, due to the rapid urbanization in China, large areas of lands with red clays have been converted into sites for domestic and industrial constructions. Nevertheless, few researchers focused on the effect of urea on the strength and compressibility of red clay. In this research, the shear strength and compressibility of the red clay saturated by different concentrations of the (NH₄)₂CO₃ solution (urea's hydrolysates) were experimentally investigated using direct shear as well as oedometer tests, respectively. It was noticed that both the shear strength and stiffness of the red clay significantly decreased after exposure to the urea solution. In addition, the micromechanisms of the strength and compressibility of the red clay treated by the (NH₄)₂CO₃ were studied by the scanning electron microscope test and X-ray diffraction test. Based on the test results, a new model was developed to simulate the chemomechanical behavior of saturated clayey soil by modifying the Barcelona basic model (BBM) for unsaturated soils. The proposed model introduces four additional parameters, compared to the BBM, to account for the nonlinear shear strength behavior of the red clay. This model accounts for most of the complex features related to the strength and stiffness behavior of clayey soils. The parameter calibration procedures, by using the oedometer and direct shear test results, are also presented. To validate the proposed model, experimental results from the literature are considered in which illite clay samples were either mechanically or chemically or both mechanically and chemically loaded. Part of the experimental results is used to calibrate the model parameters and the other part along with the calibrated parameters is used to verify the proposed model. A comparison between experimental data and predicted results demonstrated that the proposed model is able to capture the main features related to the chemomechanical coupling behavior of saturated soils.     

不同趋势法的宁夏长时序植被变化分析

宁夏地处黄土高原，植被变化趋势直接影响其生态保护。本文应用2005—2015年的MODIS NDVI月合成产品，并采用最大合成法得到年NDVI数据，分别利用一元线性回归法和Sen+Mann-Kendall法对宁夏11年间植被变化趋势和空间差异进行研究分析。结果表明，在月际变化上，月NDVI均值呈高斯分布，7—9月是植被长势最好的阶段；在年际变化上，2005—2007年NDVI值明显增长，2008—2012年NDVI值呈稳定性增长，2013—2015年NDVI值有下降趋势；在变化趋势上，一元线性回归法与Sen+Mann-Kendall法得到的植被变化趋势基本一致，均表现为北部植被整体改善，但局部城区植被退化较为严重；中部地区轻微改善，局部存在明显改善；南部植被有明显改善且植被改善面积较大；通过差异性分析二者差异性仅为22.95%，且Sen+Mann-Kendall法能更好地监测轻微变化区域，变化趋势更加准确。     

海底多金属硫化物自然电位观测方式研究

利用海洋自然电位法可以探测海底多金属硫化物矿体的位置和轮廓。在调查过程中，可以进行水平观测和垂直观测，本文对这两种观测方式的探测效果进行数值模拟分析，结果表明垂直观测异常大，对矿体的横向分辨率高。但在进行垂直观测时，电极离底低，工作风险大。所以在实际调查过程中，需要根据需求选择合适的观测方式。另外，在实际测量过程中，电极对会偏离垂直方向和水平方向，将导致异常结果发生变化，因此在数据资料处理与解释过程中要注意。本文可以为海底多金属硫化物自然电位调查提供参考。     

近45年涠洲岛5次珊瑚热白化的海洋站SST指标变化趋势分析

根据涠洲岛珊瑚礁普查(Reef Check)历史资料和涠洲岛海洋站实测海表温度(SST)历史资料,采用对比分析与相关分析方法,分析1966―2010年该岛珊瑚热白化的SST指标变化特征,结果显示:1)涠洲岛珊瑚热白化的最热周平均SST值为31.6℃或最热日平均SST值为32℃;2)1966―2010年涠洲岛的逐年最热月月均SST、最热日日均SST、年极端最高SST及最热周平均SST呈准同步变化,彼此间的相关系数为0.71~0.89,4种珊瑚热白化SST指标没有显著上升趋势;3)最热月月均SST和最热周平均SST的变化趋势与全球变暖在统计上存在显著相关关系。     

洞庭湖区湿地恢复的生态补偿效应(英文)

Eco-compensation is an environmental economic instrument for internalization of external cost.Returning farmland to lake is one of the important parts of restoring wetland ecosystem function in the Yangtze River Valley of China.Whether the project of lake recovery can be successful depends on the compensation to the farmers who have lost their original benefits and contributed to the wetland ecosystem recovery by returning farmland to lake.Aiming at the wetland recovery of the Dongting Lake,the practical im...     

GPS高精度重复测量中的天线相位中心偏差检测及改正

首先通过GPS接收机在超短基线上检测数据计算天线相位中心偏差,然后对民乐跨断层综合观测场地2007~2008年的GPS点位速率进行校正。从计算结果可知,所用GPS天线相位中心偏差多在亚毫米级。对于距离在几千米的点位,由于各期观测所用天线的不同,使得相位中心的偏差对水平运动速率的影响多在亚毫米级;若各期观测所用天线相同,则影响多在10-2毫米量级。对高精度GPS观测来说,多期观测尽可能采用同一天线。     

云南金平龙脖河铜矿区变钠质火山岩组分迁移及与成矿的关系

金平龙脖河铜矿位于哀牢山-金沙江构造带的东南端。赋矿围岩为变钠质火山岩,成矿主要类型为构造破碎蚀变岩型铜矿;围岩蚀变以绿泥石化、碳酸盐化、硅化、磁铁矿化等为主。通过对产于变钠质火山岩中不同蚀变程度和矿化程度岩、矿石的地球化学组分进行对比,计算不同岩、矿石体积的变化和组分的迁移。计算结果表明：从弱矿化变钠质火山岩到强矿化变钠质火山岩,随蚀变和矿化的增强,岩石体积分别扩容了14%、12%;组分SiO2、HREE及成矿物质Cu和S等的含量具有逐渐增加的趋势,微量元素中亲铁元素Cr、Ni也有不同程度的迁入富集;而组分CaO、MnO和LREE等的含量则逐渐降低,说明成矿过程中SiO2、HREE及成矿物质Cu和S等是由流体带入的,而CaO、MnO和LREE等则是由流体从围岩中带出的,以及成矿物质主要来源于深部流体。     

南海北部陆坡白云深水区深水沉积结构要素

在回顾深水沉积结构要素研究的基础上,结合白云深水区的勘探实践,对白云深水区深水沉积的结构要素进行了研究。将白云深水区深水沉积划分为4种结构要素,分别为水道、天然堤-溢岸沉积、席状砂和块体搬运沉积。水道是白云深水区深水沉积的主要组成部分,也是重要的储层;水道按成因可分为侵蚀型、侵蚀/加积型和加积型;水道充填沉积物的岩性变化较大,有砾岩、砂岩、泥岩以及几种岩性的混合。天然堤-溢岸沉积主要以泥岩、粉砂岩为主,平面上,天然堤-溢岸沉积与水道走向平行,横向上远离水道扩散,侧向连续性好但垂向连续性差。席状砂位于水道末端,具有朵叶状外形,分为层状和合并状2种类型：层状席状砂具有相对低的砂岩体积分数,泥岩和砂岩互层;而合并状席状砂岩体积分数高,砂层和砂层接触,夹有少量的泥。块体搬运沉积包括滑塌、滑块、块体流、碎屑流、坡身失稳复合体、块体搬运复合体等;块体搬运沉积常直接位于层序界面上,对下伏地层侵蚀明显,分布广泛,可作为良好的油气封盖层。     

高分辨率实时监测技术在岩溶碳汇估算中的应用——以板寨地下河监测站为例

岩溶作用对大气CO₂起到汇的作用,其量级的大小受岩溶水的排泄量及由岩溶作用产生的无机碳浓度两方面的影响。基于贵州茂兰国家级自然保护区板寨地下河监测站的监测数据,对岩溶碳汇过程及其影响因子进行了分析。结果表明,板寨地下河流域岩溶年碳汇量约为353 t C,不同时间尺度的岩溶碳汇强度与流域的排泄量之间均存在良好的线性关系。因此,能否准确监测岩溶地下河的排泄量是岩溶碳汇估算的关键。由于岩溶区水循环季节变化幅度较大,具有实时监测功能的监测站在岩溶碳汇评估中显得十分必要。     

Using large dynamite shots to image the structure of the Moho from deep seismic reflection experiment between the Sichuan basin and Qinling orogen

The Qinling orogen was formed as a result of the collision between the North and South China blocks. The Qinling orogen represents the location at which the southern and northern parts of the Chinese mainland collided, and it's also the intersection of the Central China orogen and the north-south tectonic belt. There is evidence of strong deformation in this orogen, and it has had a long and complex geological history. We investigated the structure of the Moho in the southern Qinling orogen using large dynamite shot imaging techniques. By integrating the analysis of the single-shot and the move-out corrections profile, we determined the structure of the Moho beneath the northern Dabashan thrust belt and the southern Qinling orogen, including the mantle suture beneath Fenghuang mountain. The Moho is divided into two parts by the mantle suture zone beneath Fenghuang mountain:(1) from Ziyang to Hanyin, the north-dipping Moho is at about45–55 km depth and the depth increases rapidly; and(2)from Hanyin to Ningshan, the south-dipping Moho is at about 40–45 km depth and shallows slowly. The mantle suture is located beneath Fenghuang mountain, and the Moho overlaps at this location: the shallower Moho is connected to the northern part of China, and the deeper Moho is connected to the southern part. This may indicate that the lithosphere in the Sichuan basin subducts to the Qinling block and that the subduction frontier reaches at least as far as Fenghuang mountain.