Determination of hydraulic conductivity of sand-bentonite mixtures for engineering purposes   总被引：1，自引：0，他引：1  

Göran Sällfors  Anna-Lena Öberg-Högsta 《Geotechnical and Geological Engineering》2002,20(1):65-80

Pollution of the environment due to leakage from waste repositories is a well-known and wide spread problem. Emphasis has therefore been put on design of liners for such repositories, focusing on hydraulic conductivity and its variation with time, liner composition, water content, compaction etc. The paper addresses the hydraulic conductivity of sand/bentonite mixtures, especially the variation of the hydraulic conductivity as a function of bentonite content, compaction and degree of saturation. In order to better understand the variation of the hydraulic conductivity of a sand–bentonite mixture a new parameter k ₁ has been proposed. The parameter reflects the amount of bentonite per pore volume and can easily be calculated based on the amount of bentonite and the dry density of the soil mixture. Thereby, the hydraulic conductivity can be predicted as a function of different degres of compaction. This method can be used for engineering purposes to predict the hydraulic conductivity at an early stage of a design to get an idea of the required design and hence, cost.  相似文献   

印尼某电站基桩的负摩阻力及其措施     

艾传井 《地质科技情报》2005,24(Z1):89-92

基于印尼某电站场地的工程地质条件,根据基桩负摩阻力的产生机理,分析确定了中性点的位置,计算了负摩阻力产生的下拉荷载;并结合膨润土泥浆护壁的作用机理,计算了采取较大直径预钻孔和膨润土泥浆护壁的措施后负摩阻力产生的下拉荷载.计算结果表明,前者大于单桩承载力设计值,因此不能采用预应力混凝土管桩方案;后者较前者显著降低,约为单桩承载力设计值的50%,因此可以采用预应力混凝土管桩方案.  相似文献   

四川三台膨润土的基本物化性能及其对铅、钴的吸附性研究   总被引：1，自引：0，他引：1  

易发成  杨剑  李玉香  李虎杰  张东  石正坤 《矿物岩石》2004,24(4):39-42

对四川三台钙基膨润土的基本物化性能和对Pb^2 ，Co^2 离子的吸附性能作了初步的研究。基本物化性能主要包括化学成分、阳离子交换容量、密度、比表面积、孔径、渗透系数及热稳定性。通过实验得出：1)经过钠化改型并酸化处理后的膨润土的阳离子交换容量(CEC)明显高于未经处理的原土；2)膨润土的最佳酸活化条件为在96℃左右以15％的硫酸活化4小时的性能最佳；3)膨润土土的密度为2．11g／cm^3，颗粒密度钠化土为1．996g／cm^3，原土为2．079g／cm^3；渗透系数为0．013cm／s(20C)；体积平均粒径为30．950μm；比表面积为329．7482m^2／g，平均孔径为33．238nm；4)膨润土对对重金属离子的吸附实验，得出膨润土对重金属离子Pb^2 的吸附性能优于Co^2 ，Pb^2 和Co^2 的吸附比(Rd)分别为167．8ml／g及53．3ml／g；Pb^2 和Co^2 去除率(r)分别为45．87%和21．20％。  相似文献   

Erosion of bentonite particles at the interface of a compacted bentonite and a fractured granite     

Min-Hoon Baik  Won-Jin Cho  Pil-Soo Hahn 《Engineering Geology》2007,91(2-4):229-239

Compacted bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste. An erosion of bentonite particles caused by a groundwater flow at the interface of a compacted bentonite and a fractured granite was studied experimentally under various geochemical conditions. The experimental results showed that bentonite particles could be eroded from a compacted bentonite buffer by a flowing groundwater depending upon the contact time, the flow rate of the groundwater, and the geochemical parameters of the groundwater such as the pH and ionic strength.

A gel formation of the bentonite was observed to be a dominant process in the erosion of bentonite particles although an intrusion of bentonite into a rock fracture also contributed to the erosion. The concentration of the eroded bentonite particles eroded by a flowing groundwater was increased with an increasing flow rate of the groundwater. It was observed from the experiments that the erosion of the bentonite particles was considerably affected by the ionic strength of a groundwater although the effect of the pH was not great within the studied pH range from 7 to 10. An erosion of the bentonite particles in a natural groundwater was also observed to be considerable and the eroded bentonite particles are expected to be stable at the given groundwater condition.

The erosion of the bentonite particles by a flowing groundwater did not significantly reduce the physical stability and thus the performance of a compacted bentonite buffer. However, it is expected that an erosion of the bentonite particles due to a groundwater flow will generate bentonite particles in a given groundwater condition, which can serve as a source of the colloids facilitating radionuclide migration through rock fractures.  相似文献   

辽宁省二道河膨润土矿床地质特征及成因探讨     

刘殿鹤  张雪花 《化工矿产地质》2015,(2):85-92

二道河膨润土矿床位于辽宁西部紫都台-于寺盆地北东缘义县期火山断陷盆地内,矿体赋存于义县组沉凝灰岩及流纹质熔结凝灰岩、珍珠岩等中酸性火山碎屑岩中。矿区共发育70多条层状、似层状膨润土矿体。主要矿石矿物为蒙脱石,具改型特征。浅部主要为钙基膨润土,200m标高以下向钠基膨润土转变。经综合研究认为,该矿床属典型的以后期表生风化淋滤型作用为主的复成因矿床。  相似文献   

鄂尔多斯盆地西、南缘奥陶纪地质事件群耦合作用   总被引：5，自引：0，他引：5  

王振涛  周洪瑞  王训练  张永生  景秀春  邢恩袁 《地质学报》2015,89(11):1990-2004

北祁连造山带和北秦岭造山带在早古生代经历了相似的洋陆转化过程,于奥陶纪时发育了汇聚板块边缘的沟-弧-盆体系,分别形成了北西向展布的北祁连造山带走廊南山北缘早古生代岛弧及弧后盆地和东西向展布的北秦岭造山带早古生代岛弧及弧后盆地。期间,秦岭-祁连洋的俯冲造山作用和鄂尔多斯盆地西南缘沉积类型和内陆湖盆的发展演化之间存在有机的联系,构成了盆-山耦合体系,引发一系列构造事件、火山喷发事件和多种类型的事件沉积等。它们之间存在着一系列成因机制上的联系,有着共同的宏观背景。鄂尔多斯盆地西、南缘在几乎相同时期存在一次构造背景的转变,由被动大陆边缘转化为主动大陆边缘,并诱发了多期火山喷发事件,在盆地西南缘奥陶系形成多套斑脱岩夹层,这些斑脱岩可能为同时期或者稍后的钾盐矿(包括含钾卤水)的形成提供了重要物源。同时,鄂尔多斯盆地南缘由浅水碳酸盐台地陷落为深水斜坡,在盆地西、南缘奥陶系有规律的集中发育重力流沉积(海底扇、浊积岩等)、滑塌沉积和震积岩等事件沉积。从形成机制上,华南板块向北俯冲触发了火山活动和地震,火山喷发在奥陶系集中沉积了多套凝灰岩夹层,地震活动导致同时期大套重力流沉积,并触发相对深水区沉积物向深水区移动,使得重力流沉积转化为浊流沉积,形成了具有良好储层的浊积岩。统计表明,上述事件发育的时间与秦岭地区构造活动相对最活跃的时期基本一致。因此这些分布稳定的凝灰岩薄层和中奥陶世集中有规律分布的重力流沉积砂体为华南板块向华北本快俯冲背景下形成的,它们之间存在耦合关系。  相似文献   

γ辐照对改性钠基膨润土影响的初步研究   总被引：1，自引：0，他引：1  

梁栋  刘伟  杨仲田  郭喜良  杨卫兵  李洪辉  赵帅维 《矿物学报》2015,35(1):103-106

为了确认γ辐照对改性钠基膨润土的影响,拓展高放地质处置缓冲材料性能评价范围,以内蒙古高庙子改性钠基膨润土为研究对象,利用红外光谱分析仪、同步热分析仪和X射线衍射仪分析了不同γ辐照剂量(1000、2000、3000、4000和5000 k Gy)对改性钠基膨润土性能和微观结构的影响。结果表明:在5000 k Gy大剂量γ辐照后,高庙子改性钠基膨润土中某些官能团发生了少量的化学转变,耐热性能有所提高,但对钠基膨润土中的层间水和吸附水影响不大;另外其微观结构变化不明显,只是晶胞尺寸有所减小;总体而言,高庙子钠基膨润土在大剂量γ辐照环境中稳定性是良好的。  相似文献   

Evaluation of Engineering and Cement–Stabilization Parameters of Clayey–Sand Mixtures under Soaked Conditions     

Evangelos?I.?StavridakisEmail author 《Geotechnical and Geological Engineering》2005,23(6):635-655

Clay soils, especially clay soils of high or very high swelling potential often present difficulties in construction operations. However, the engineering properties of these clay soils can be enhanced by the addition of cement, thereby producing an improved construction material. Higher strength loss of cement stabilized clay soils after soaking in water is attributed to water absorbing capacity of the clay fraction (e.g. montmorillonite). Kaolinite and illitic soils are largely inert and resist to water penetration. These clays generally develop satisfactory strengths resulting to low strength reduction [Croft, 1967]. The swelling clays such as bentonite soaked in water, due to environmental conditions, result to volume increase causing macro and micro-fracturing in engineering structures. These fractures accelerate water penetration and consequently cause greater strength loss [Sällfors and Öberg-Högsta, 2002]. The water intrusion during soaking creates swelling and disrupts the cement bonds. The development of internal and external force systems in soil mass, due to soaking conditions, establish the initiation of slaking. Internal force system of a stabilized clayey soil consists of the resultant stresses established by the bonding potential of a cementing agent and the swelling potential of a clay fraction. In an effort to study this influence of soaking conditions and final absorbed water content on the stabilization parameters (cement, compaction, curing time), both unconfined compressive strength and slaking (durability) tests were carried out on two different cement stabilized clayey mixtures consisted of active bentonite, kaolin and sand.  相似文献   

Borehole Sealing Project at the Grimsel Test Site     

Peter Blümling 《Geotechnical and Geological Engineering》2005,23(6):843-858

Within the context of the phase IV (1994–1996) research and development activities at the Grimsel Test Site (GTS), Nagra developed, in collaboration with the Agence Nationale pour la Gestion des Déchets Radioactifs (Andra), an investigation project for the sealing of boreholes drilled from underground. The project had the following goals:

–	sealing of boreholes drilled from underground facilities with a length of up to 500 m,
–	sealing of boreholes with mainly irregular shape (e.g. breakouts of borehole wall),
–	ensuring a hydraulic conductivity of 10−11–10−12 m/s for the seal,
–	ensuring reliable quality control in routine production.

The new concept developed in this project was to use highly compacted bentonite pellets only. The two techniques tested were

(1)	pneumatic injection of pellets into a borehole using a grain size distribution of 4–10 mm,
(2)	emplacement using a modified core barrel for transport and compaction of the pellets.

Both techniques were tested in situ at the GTS to estimate their performance under realistic field conditions. The swelling pressures were monitored for 4 months after seal emplacement until an almost constant value was attained. Finally the hydraulic and mechanical performance of the seal was tested. It was found that the conductivities measured across the seal were equivalent to the matrix properties of the surrounding rock (2–5 × 10⁻¹² m/s). The hydraulic testing also showed no linear preferential flow.  相似文献   

江西广丰李家膨润土压实性能研究--高放废物处置缓冲/回填材料压实性能初探     

刘晓东罗太安  邢占文刘卫卫 甄啸 《华东地质学院学报》2004,27(1):19-23

研究了广丰李家钠基膨润土的压实性能,得出了不同压实功作用下,膨润土干密度与含水率之间的关系．以及粒径、压实功等因素对压实性能的影响;在相同压实功和相同含水率条件下,膨润土粒径较小时相对应的干密度较小．当压实功为2684．9kJ／m^3时,钠基膨润土的最大干密度可达1．525g／cm^3,最优含水率为26．30％。首次选用石英砂作为添加荆,探索了添加荆对膨润土压实性能的改善作用,实验结果说明石英砂添加荆的加入可以大大提高膨润土的干密度。减小对应的最优含水率,并得出约10％的石英砂是添加剂的最佳用量。该研究结果为钠基膨润土作为高放废物处置库缓冲／回填材料的性能评价提供了重要的依据。  相似文献