软板岩膨胀特性试验及微观机制分析   总被引：1，自引：0，他引：1  

左清军  吴立  袁青 《岩土力学》2014,35(4):986-990

针对软板岩内部特殊的构造及其遇水膨胀的特点,以湖南省怀化芷江地区的板岩为例,选取14组岩样分别进行矿物成分、微观结构测试和侧向约束膨胀试验,研究软质板岩的膨胀特性及其微观机制。结果表明:软质板岩侧向约束膨胀率与吸水时间之间呈指数函数关系,在试验早期,侧向约束膨胀率随吸水时间的延长而增大,且增长速率较快,侧向约束膨胀率-吸水时间关系曲线较陡;在试验后期,侧向约束膨胀率趋于稳定,侧向约束膨胀率-吸水时间关系曲线由陡变缓。侧向约束膨胀率随着吸水率的增长呈乘幂函数关系增长,在试验早期增长较快,而后增长速率变小,直至最后趋于稳定。轴向膨胀率随轴向荷载的增加呈负对数函数减小,初期减小幅度较大,后期逐渐变低。结构面方向和试样轴向的夹角α在区间[0°,90°]之间变化时,极限侧向约束膨胀率随着夹角α的增大而减小。  相似文献   

Use of shredded tyre waste in improving the geotechnical properties of expansive black cotton soil     

Amit Srivastava  Shikha Pandey  Jeeshant Rana 《Geomechanics and Geoengineering》2014,9(4):303-311

In recent years, geotechnical engineers are using tyre waste to alter the properties of soil for providing sustainable solutions to complex engineering problems. It is noted that black cotton soil, which is expansive in nature, covers a major portion of the Indian sub-continent, such as the Deccan plateau, Malwa plateau and a portion of Gujarat and poses challenging problems to infrastructural development in the region. In the present study, authors have characterised the geotechnical properties of black cotton soil, which is partially replaced with 4.75 mm passing – 2 mm retained (coarse fraction) and 2.0 mm passing - 75 micron retained (fine fraction) shredded tyre waste. The results of the experimental studies clearly show that partial replacement of black cotton soil with shredded tyre waste alters the geotechnical properties favourable to engineering applications and greatly reduces the swelling potential of the black cotton soil. It is noted that instead of fine fraction (2.0–0.075 mm), replacement with coarse fraction (4.75–2.00 mm) of shredded tyre waste can better be used for light weight fill behind the retaining walls as well as for embankment construction as it helps in reducing swelling pressure as well as improving the strength properties.  相似文献   

论广西红粘土的胀缩性能     

曾秋鸾 《南方国土资源》2000,13(3):75-77

文章从由碳酸盐岩溶余堆积形成的红粘土引起产生的地裂、房裂等不良工程地质现象入手,以大量的实验资料为基础,指出广西红粘土的胶粒含量,可塑性指标高,具有较强的吸附能力和较强的亲水性,自由膨胀率接近或等于27%.论述了红粘土液限和塑限值在塑性图上的分布规律与一般膨胀土的分布规律相吻合,这种粘土应属于弱至中等级膨胀性粘土,并以收缩变形为其主要特征.  相似文献   

浅议非饱和土基坑无支护开挖深度的确定     

陆秋生  阎长虹 《地球科学与环境学报》2003,25(3):52-55

在D.G.Fredlund等的非饱和土抗剪强度理论及其延伸的Rankine土压力公式以及国内学者卢肇钧等近年来的研究成果(用膨胀力代替基质吸力来刻画非饱和土的抗剪强度)的基础上,推导了含膨胀力的非饱和土竖直边坡临界高度的计算公式,初步探讨了非饱和土基坑无支护开挖深度的确定方法。  相似文献   

储层中蒙脱石碱溶相变缩膨实验研究   总被引：1，自引：0，他引：1  

朱云  曹维政  鲁安怀  王清华  李艳  张虓雷  王长秋 《矿物学报》2011,31(1):88-94

蒙脱石作为常见的粘土矿物,广泛存在于含油气盆地中。针对由于蒙脱石具有强烈亲水性,遇水体积可膨胀至原体积的数倍甚至数十倍,从而造成油气储层的水敏损害这一实际问题,对蒙脱石在强碱条件下发生结构变化与物相转变,实现降低其亲水性进行了详细的实验研究。探讨了天然钙基蒙脱石与天然钠基蒙脱石在80℃,1 mol/L KOH溶液中所发生的相变过程;通过XRD、SEM、TEM等测试手段分析查明其碱溶相变最终产物主要是微米级纤维状、柱状、颗粒状的菱沸石和麦钾沸石,均为不具膨胀性的架状硅酸盐矿物;最后通过自由膨胀实验证实蒙脱石碱溶产物膨胀性较原矿物显著降低。研究成果为转化油气盆地中"水敏性"粘土矿物,降低油气储层水敏损害,保护储层与提高采收率,提供了新的思路。  相似文献   

Numerical analysis of an experimental pipe buried in swelling soil     

Pathmanathan Rajeev  Jayantha Kodikara 《Computers and Geotechnics》2011

This paper investigates the pipe–soil interaction for pipes buried in expansive soil when subjected to swelling soil movement due to increase in moisture content. A laboratory experiment has been undertaken on a plastic pipe in a large-scale pipe box. A three dimensional numerical model is developed to analyse the pipe response, using FLAC^3D computer program. The pipe is assumed to behave as a linearly elastic material, while the soil is modelled as a nonlinear material with Mohr–Coulomb failure criterion. The water flow and soil/pipe deformations are decoupled, where water flow is calculated using simplified capillary rise theory on the basis of measurements made. A reasonably good agreement between the experimental results and model predictions is reported.  相似文献   

Swell–consolidation characteristics of artificial sand clay mixes     

《Geomechanics and Geoengineering》2013,8(1):69-74

Many remedial measures have been devised to lessen the damage caused by expansive soils. Physical alteration, chemical stabilization, innovative foundation techniques like belled piers, drilled piers, under-reamed piles and granular pile anchors are some of these remedial measures. Mixing a non swelling material such as gravel or sand to expansive soil is one of the methods of physical alteration. This paper presents experimental data on artificially prepared sand-clay mixes. Swell and consolidation characteristics of these artificially prepared sand-clay mixes were studied in one dimensional consolidometer. Fine sand content and fines content in the expansive soil were arbitrarily varied in the investigation. The fines content was varied as 425–300 μm and 150–75 μm, separated from the same expansive soil based on the grain size. Swell potential and swelling pressure decreased with increasing fine sand content but increased with increasing fines content. Coefficient of compressibility, coefficient of volume compressibility and compression index of the samples decreased initially up to a sand content of 15% and thereafter increased at higher sand contents.  相似文献   

重塑上海软土的压缩和剪切变形特性试验研究   总被引：2，自引：1，他引：1  

孙德安  陈波  周科 《岩土力学》2010,31(5):1389-1394

根据典型上海软土重塑土样的等向压缩试验,测K0与不测K0的单向压缩试验结果,得到不同试验条件下的压缩指数Cc和膨胀指数Cs,并分析了它们之间的关系。进行三轴排水剪切试验,得到了重塑上海软土在不同超固结比和围压下的变形和强度特性,并计算出重塑上海软土的内摩擦角。最后,根据一组不同荷载下的长期单向压缩试验结果,得到重塑上海软土的次压缩系数C?与荷载之间的关系。上述研究得到的初步结论及相关参数可为工程实践、超固结上海软土本构模型的建立提供参考数据。  相似文献   

掺砂率对膨润土与砂混合物膨胀特性的影响     

孙文静  刘仕卿  孙德安  魏振飞 《岩土力学》2016,37(6):1642-1648

膨润土与砂混合物的膨胀特性是评估核废料深层地质处置工程长期性能的重要指标。对比不同膨润土及其与砂混合物的膨胀试验结果可知,对纯膨润土及其低掺砂率混合物,浸水膨胀完成后蒙脱石孔隙比em与竖向应力?v在双对数坐标内呈惟一的线性关系,利用该线性关系可预测浸水完成后不同竖向应力下的体积变化量及不同初始状态对应的膨胀力;对高掺砂率混合物,在砂骨架形成之前,em-?v线性关系成立,随着竖向应力的增大,砂骨架形成,对应的em值脱离em-?v线性关系,混合物中掺砂率越大,脱离该线性关系时的竖向应力就越小。砂骨架形成前,砂颗粒被蒙脱石包围,外力由蒙脱石承担,最终变形量由试样中单位体积蒙脱石的含量决定;砂骨架形成后,竖向应力最终由砂骨架和蒙脱石共同承担。利用砂骨架孔隙比的概念可确定各种不同掺砂率混合物形成砂骨架时的应力起偏点。同时,还可确定混合物能够形成砂骨架的掺砂率范围。  相似文献   

膨胀性硅藻土的力学性质及其灾害效应研究     

张永双  郭长宝  曲永新  姚鑫 《岩土力学》2013,34(1):23-30

在云南保山－腾冲高速公路建设中,遇到了与膨胀性硅藻土相关的边坡稳定问题。通过对云南腾冲五合乡、芒棒乡、团田乡多个地质剖面现场调查和室内物质成分、微观结构分析、力学性质测试表明,云南腾冲新近纪芒棒组硅藻土是一种富含膨胀性黏土矿物的黏土质硅藻土,在性状上属于膨胀性极软岩。天然硅藻土具有很强的结构性,导致其物理性质与力学性质的关系与传统岩土力学规律极不相符,如孔隙比高达2.20～2.78、液性指数为0.66～2.73的天然硅藻土单轴抗压强度竟高达1.09～2.11 MPa。综合研究表明,云南保山－腾冲高速公路建设中黏土质硅藻土边坡的滑坡灾害、风化剥落灾害与其工程特性密切相关。  相似文献