The influence of salinity on hysteresis of soil water‐retention curves

Taiwan is surrounded by the sea, and the southwestern seashores are suffering from a growing land subsidence problem caused by the excessive extraction of groundwater. There is also very serious intrusion by seawater along the coastline. These circumstances obstruct any land use, soil remediation or agriculture development in the area. When seawater intrudes, salt gets into the soil. The infiltration, evapotranspiration and the distribution of salinity in the unsaturated soil become a very complex problem. It is vital to investigate the hysteresis of soil water‐retention curves, combined with the salinity in these areas. Therefore, this study's main focus will be the calibration of variations in salinity and their effect on the hysteresis of soil water‐retention curves. In the wetting processes, the salty soil water‐retention curves undergo an upper shift compared with the original soil water‐retention curves because of the higher tension of saltwater. In the drying processes, there is also an upper shift compared with the original curves because the salinity influences the air‐entry pressure. The saltwater's high salinity causes the hysteresis of soil water‐retention curves to experience a greater shift. The changes in salinity also cause changes to the hysteresis curves’ shape factors, which conforms to Huang's model (developed by Huang H.C., Y.C. Tan, C.W. Liu, and C.H. Chen in 2005), the values of α and n. The value of α decreases with the increased salinity. The trend of the n value presents an irregular result. A linear regression of the α^w and α^d values was advanced where the R‐square values of α^w and α^d exceeded 0.97. Copyright © 2012 John Wiley & Sons, Ltd.     

生石灰激发GGBS固化高含水率香港海相沉积物的物理力学性质研究

海相沉积物处置已成为一项全球范围的挑战。在传统固化/稳定化方法中,环境污染严重的波兰特水泥(PC)是一种被广泛使用的固化剂。在此背景下,一种环境友好型的固化剂(生石灰与粒化高炉矿渣(简称GGBS)的混合料)取代PC来用在土壤改良领域。使用生石灰激发GGBS固化处理高含水率海相沉积物,并与PC固化海相沉积物进行比较。通过物理、化学试验及无侧限抗压强度试验分析了生石灰-GGBS固化海相沉积物的物理、化学和强度特性。结果表明:与PC固化海相沉积物相比,生石灰-GGBS固化沉积物具有体积收缩大、含水率低和密度略高的物理特性。随着生石灰比例的降低和养护时间的延长,生石灰-GGBS固化沉积物的pH值逐渐降低。生石灰-GGBS固化沉积物的无侧限抗压强度呈先增大(生石灰:固化剂为0.05～0.15)后减小(生石灰:固化剂为0.15～0.3)再增大(生石灰:固化剂为0.3～0.4)的趋势;当生石灰与固化剂的比值为0.15及0.4时,强度达到最大值;当生石灰与固化剂的比值为0.15时,生石灰-GGBS固化沉积物达到的峰值强度是相同条件下PC固化沉积物强度的1.4倍。该研究结果证实了GGBS与少量生石灰组合...     

MICP技术联合多孔硅吸附材料对锌铅复合污染土固化/稳定化修复的试验研究

近年来,工业和科技的快速发展使得重金属污染土固化/稳定化的修复研究成为热点。运用微生物诱导碳酸钙沉淀(MICP)技术联合吸附材料对锌铅复合重金属污染土进行固化/稳定化的修复,通过无侧限抗压强度试验、毒性浸出试验,评价处理前后污染土的固化效果与重金属的稳定化效果,结合扫描电镜(SEM)和X射线衍射(XRD)等检测手段,揭示MICP技术处理锌铅重金属污染土的修复机制。研究结果表明,采用MICP技术对锌铅重金属污染土进行固化/稳定化之后,可以有效降低污染土中有害重金属的浸出性。当矿化时间为10d时,试样无侧限抗压强度为942.5k Pa;铅的浸出浓度为4.20mg/L,比未处理时降低了44.81%;锌的浸出浓度为4.31mg/L,比未处理时降低了46.19%,效果显著。在此基础上,添加10%的多孔硅吸附材料后,试样无侧限抗压强度可达到1 021 kPa,强度提高了8.3%;铅的浸出浓度为2.45mg/L,与未经处理时相比,降幅达到了67.81%,与单纯MICP方法处理时相比,铅浸出浓度被二次降低了41.67%;锌的浸出浓度仅为2.93 mg/L,与未经处理时相比,降幅达到了63.4%,与单纯...     

Pullout behavior of biocement–geosynthetic reinforcement system: a parametric study

Acta Geotechnica - In the biocement–geosynthetic system, biocement is combined with geosynthetic to increase the pullout resistance of the geosynthetic and thereby the stability of reinforced...     

松辽盆地开鲁坳陷西部四方台组铀成矿条件及找矿方向

开鲁坳陷位于松辽盆地西南部,通过系统地分析开鲁坳陷西部铀源、构造、岩性-岩相、砂体氧化-还原、水文地质和铀矿化特征,笔者认为区内四方台组具备砂岩型铀矿成矿的基本地质条件。经统计蚀源区和地层本身砂体铀含量,数据显示该区具备丰富的内外双重铀源。深部还原流体可沿主干断层直接进入四方台组,这些断层也为地下水排泄提供通道。四方台组发育冲积扇、辫状河沉积体系,泥-砂-泥结构稳定,具备良好的地下水补-径-排和水中铀水文地质条件。文章从氧化带、砂体Th/U值变化规律、Fe²⁺/Fe³⁺值及有机碳含量分布特征等方面阐述其与铀成矿的关系。铀成矿主要受铀源、构造、岩性岩相及砂体氧化-还原等关键因素控制,各种成矿要素匹配良好,具备形成中型及以上砂岩型铀成矿潜力。     

大兴安岭南段工农屯地区上侏罗统玛尼吐组火山岩U- Pb年龄、地球化学特征及其成因

内蒙古扎鲁特旗工农屯地区玛尼吐组火山岩位于大兴安岭南段,LA-ICP-MS锆石U-Pb年龄为149±1.1Ma,形成时代为晚侏罗世。地球化学特征显示SiO₂(58.14%～63.69%),Al₂O₃(16.31%～18.66%),Fe₂O₃(3.17%～5.39%),K₂O+Na₂O(6.58%～7.86%),MgO(0.82%～2.04%),Mg^#(25～41)。研究区玛尼吐组安山岩属于准铝质—弱过铝质高钾钙碱性岩石。稀土元素总量为136.41×10^-6～163.64×10^-6;轻稀土和重稀土元素之比为7.22～10.02,均值为8.42。(La/Yb)_N为7.70～10.44,均值8.95;(La/Sm)_N为3.18～3.77;因此可知轻稀土元素要比重稀土元素富集程度高,轻重稀土内部存在明显的分馏。δEu为0.84～0.9...     

Formation conditions and reservoir-forming models of the Ordovician buried hill reservoirs in the Jizhong depression

The buried hill in the Jizhong depression contains abundant petroleum reserves and are important production areas. The Ordovician buried hill has restricted the discovery of new oil and gas exploration targets because of its strong reservoir heterogeneity and complex reservoir-controlling factors. Based on a large volume of core, thin section, logging, seismic, and geochemical data and numerous geological analyses, the reservoir-forming conditions and modes were systematically analyzed to guide the exploration and achieve important breakthroughs in the Yangshuiwu and Wen’an slope buried hills. The study revealed that three sets of source rocks of the third and fourth members of the Shahejie Formation from the Paleogene and Carboniferous-Permian were developed in the Jizhong depression, providing sufficient material basis for the formation of buried hill oil and gas reservoirs. The reservoir control mechanism involving the three major factors of “cloud-karst-fault” was clarified, and karst cave, fracture fissure-pore, and cloud pore type reservoir models were established, thereby expanding the exploration potential. Controlled by the superposition of multi-stage tectonic processes during the Indosinian, Yanshanian, and Himalayan, two genetic buried hill trap types of uplift-depression and depression-uplift were formed. Based on the analysis of reservoir-forming factors of the Ordovician buried hill, three buried hill oil and gas reservoir-forming models were identified: low-level tectonic-lithologic composite quasi-layered buried hill, medium-level paleo-storage paleo-block buried hill, and high-level paleo-storage new-block buried hill. Comprehensive evaluations indicate that the reservoir-forming conditions of the low-level tectonic-lithologic composite quasi-layered buried hill in the northern portion of the Jizhong depression are the most favorable and that the Sicundian and Xinzhen buried hills are favorable areas for future exploration.     

Energy dissimilation characteristics and shock mechanism of coal-rock mass induced in steeply-inclined mining: comparison based on physical simulation and numerical calculation

Acta Geotechnica - In recent years, as the Urumqi mining area deepens, rockbursts induced by the instability of the coal-rock mass are becoming more serious in steeply-inclined coal seam mining....