Influence of relative compaction and degree of saturation on the deformation characteristics of bentonite under freeze-thaw cycles

Bentonite,consisting of clay minerals of the montmorillonite group,has been widely used as an adsorbent and backfill material in nuclear waste disposal and groundwater remediation.It is challenging to use bentonite as a filling material in cold regions since bentonite is highly sensitive to thermal environmental changes,during which its bulk volume and microstructure change significantly.In this study,a series of one-dimensional and three-dimensional freeze-thaw tests were carried out within a closed system to investigate the influencing factors of the deformation of bentonite under freeze-thaw cycles.Results show that the initial soil water content greatly impacts bentonite's deformation during freeze-thaw cycles.For an initial higher degree of saturation(Sr),the expansion caused by the formation of ice lenses has a greater impact than the shrinkage induced by dehydration,ice-cementation,and so on.Conversely,bentonite tends to shrink at a lower degree of saturation during freezing.And the critical degree of saturation that determines bentonite's behavior of frost heave or frost shrinkage seems to be roughly 0.8.As the number of freeze-thaw cycles rises,initially uncompacted bentonite clay becomes more compacted,and initially compacted bentonite clay remains unchanged.

Laboratory investigation on relationship between degree of saturation, B-value and P-wave velocity

实验室测试在 Toyoura 沙标本上被执行调查在浸透 S 的度之间的关系 < 潜水艇 class= “ a-plus-plus ” > r ,B 值和 P 波浪速度 V < 潜水艇 class= “ a-plus-plus ” > p 。毛孔水(通风 de 的水或自来水) 和毛孔气体的不同类型(空气或公司 < 潜水艇 class= “ a-plus-plus ” > 象背压力的不同大小一样的 2 ) 被用来完成不同 S < 潜水艇 class= “ a-plus-plus ” > r ( 或 B 值) 。在 B 值和 V 之间的测量关系 < 潜水艇 class= “ a-plus-plus ” > p 不与理论预言一致。测量表演 V < 潜水艇 class= “ a-plus-plus ” > 在与通风 de 的水冲洗的标本的 p 价值独立于 B 值(或 S < 潜水艇 class= “ a-plus-plus ” > r ) 并且总是在处于充分浸透的状况的附近。然而， V < 潜水艇 class= “ a-plus-plus ” > 在与自来水冲洗的标本的 p 价值与在 V 之间的关系的 B 值，而是形状增加 < 潜水艇 class= “ a-plus-plus ” > p 和 B 值与理论预言相当不同。对在实验室测量和理论预言之间的差异的可能的解释躺因为空气作为空气水泡并且因此在水里存在毛孔液体(空气水混合) 是异构的而不是同质在理论预言假定。

Estimation of the Degree of Saturation of Shallow Soils from Satellite Observations to Model Soil Slips Occurred in Emilia Romagna Region of Northern Italy

For the development of alert systems for soil slip occurrence, it is important to evaluate the degree of saturation of shallow soils (Sr) over wide areas. Taking into account the possibility to estimate spatial and temporal variation of soil moisture using remote sensing techniques, a possible correlation between Sr and the daily output of a sequential data assimilation system called ACHAB (Assimilation Code for HeAt and moisture Balance) has been studied. ACHAB is based on integrated use of remotely sensed land surface temperature (LST) and common data on meteorological forcing such as air temperature, wind-speed and incident solar radiation. The aim of this study is to understand if it is possible to use ACHAB output (a daily value of evaporative fraction for the whole Italian territory) to define the parameter Sr that could be introduced in a simplified model for the description of soil slip triggering mechanisms on territorial scale.

Determining the degree of saturation of rocks as a function of time:A case study from mountainous area of Turkey

The aim of this study is to scrutinize whether, in terms of saturation, the 48 hour duration suggested by ISRM(International Society for Rock Mechanics) methods and ASTM(American Society for Testing and Materials) standard in rocks is sufficient or not, and to examine how the degree of saturation of rocks may be determined as a function of time. For this purpose, samples from five different rock groups including igneous(andesite, granite, andesitic tuff) and sedimentary(limestone, sandstone) exposed in Gümü?hane city which is from mountainous area of north-eastern Turkey, have been compiled. Measurements were taken on the samples left for saturation under laboratory conditions as a result of which the degree of saturation values at the end of these time periods were determined. Similarly, at the end of 48 hours, the samples were left to dry under atmospheric conditions in the laboratory environment and their time dependent degree of saturation were also calculated at different times. The changes as a function of time in the degree of saturation were then examined mathematically using non-linear, exponential and logarithmic functions. Graphs and equations related with the acquired time-degree of saturation values and the correlation coefficient(r) values for these equalities have indicated a high accordance between time and degree of saturation for the studied rock groups. The applied methodology will be beneficial for determining the degree of saturation based on time for engineering studies that will be carried out in similar lithologies.

Modeling of Surface Waves in a Fluid Saturated Poro-Elastic Medium under Initial Stress Using Time-Space Domain Higher Order Finite Difference Method

In this present context, mathematical modeling of the propagation of surface waves in a fluid saturated poro-elastic medium under the influence of initial stress has been considered using time dependent higher order finite difference method (FDM). We have proved that the accuracy of this finite-difference scheme is 2M when we use 2nd order time domain finite-difference and 2M-th order space domain finite-difference. It also has been shown that the dispersion curves of Love waves are less dispersed for higher order FDM than of lower order FDM. The effect of initial stress, porosity and anisotropy of the layer in the propagation of Love waves has been studied here. The numerical results have been shown graphically. As a particular case, the phase velocity in a non porous elastic solid layer derived in this paper is in perfect agreement with that of Liu et al. (2009).

EFFECT OF Si CONTENT ON ORDERING DEGREE AND ELECTROMAGNETIC CHARACTERISTICS IN FeSiAl ALLOYS

FeSiAl alloys ribbons synthesized by melt-quench were annealed in vacuum at 873 K for 60 rain. The flaky powders were prepared by milling the annealed ribbons for 70 h. After milling, the powders were heat treated at 573 K for 90 rain. The ordering degree of the powders lattice structure was analyzed by X-ray diffraction （XRD）. The measurement of specific saturation magnetization was carried out by vibrating samples magnetometer （VSM）. Complex permittivity and complex permeability in the frequency band of 0.5-18 GHz were measured with the vector network analyzer. The ordering degree of the superlattice structure increased from 0.2＇7 to 0.49. Complex permittivity and complex permeability decreased with increasing Si content. After ordering, the specific saturation magnetization decreased from 134.2 to 85.0 A.m2.kg-1. For use in anti-EMI material, the total contents of Si and Al in FeSiAl alloys should be controlled at a low level.

EFFECT OF ANTHROPOGENIC CO_2 ON THE pH AND THE SATURATION STATES OF CALCITE AND ARAGONITE OF SEAWATER

Growth of phytoplankton, zooplankton and probably most other marine organisms as well, is likely to be affected by the pH of seawater. Growth of calcareous shells and skeletons is less likely to be affect ed by the saturation states of calcite and aragonite but the dissolution is. The increase of CO2 in the oceans due to burning of fossil fuel and clearing of forests is decreasing the pH of seawater and the degress of saturation for calcite and aragonite worldwide. This paper presents the results of the first attempt to estimate the vertical distribution of anthropogenic CO2, and the decreases in pH and the degrees of saturation of calcite and aragonite in seawater near Taiwan. Most ef fects are very small except for the possible dissolution of aragonite on the upper continental slope starting around 2050 AD.

ON THE SATURATION OF L_w^p-APPROXIMATION BY (O-q'-q) TYPE HERMITE-FEJER INTERPOLATING POLYNOMIALS

The 'o' saturation theorem and the degree of Lwp, approximation by (0 - q' - q) type Hermite-Fejer interpolating polynomials for mean convergence are obtained.

单轴压缩过程中冻结砂岩的损伤局部化规律研究

损伤局部化是岩石受荷破坏过程中的必经阶段和破坏前兆特征。本文研究冻结岩石受荷破坏过程中的损伤局部化规律,并探讨初始饱和度的影响。在-20℃下对具有不同初始饱和度的冻结砂岩试样进行单轴压缩试验,并采用数字图像相关(DIC)和声发射(AE)系统采集试验过程中的表面变形和声发射信号,分析了试样表面应变局部化模式与内部微裂纹扩展类型。结果表明:(1)初始饱和度令试样的单轴抗压强度产生阶段性变化,并改变了试样各加载阶段占比和破裂过程中的声发射振铃计数分布特征;(2)以40%初始饱和度为转折点,试样的表面应变局部化模式由拉应变为主变为剪应变为主,初始饱和度超过90%时出现了拉、剪应变同时发展的混合模式,并能与试样的最终破坏形态对应;(3)损伤局部化过程中,试样内部的微裂纹扩展类型与表面应变局部化模式基本吻合。最后,结合不同初始饱和度下冻结岩石孔隙中的相组成分变化,分析了其对冻结岩石损伤局部化模式的影响。本研究有助于加深研究人员对冻结岩石力学性质的认识,为寒区岩石工程破坏与失稳预测提供重要参考。

不同初始饱和度条件下高液限滑带土环剪试验

针对某高速公路沿线边坡滑带土,开展了一系列环剪试验研究含水率对其残余强度的影响。制作1.20 g·cm^(-3)和1.35 g·cm^(-3)两种干密度条件下初始饱和度为25%、45%、65%、85%和100%的滑带土试样,在100 kPa、200 kPa和400 kPa正应力条件下开展试验,获得了滑带土剪应力与剪切角关系曲线。根据曲线得到残余剪切强度,得出滑带土的残余强度参数。结果表明,当正应力为100 kPa时,初始饱和度对滑带土残余强度影响不明显,当正应力为200 kPa和400 kPa时,初始饱和度增大将使残余强度降低。当干密度为1.35 g·cm^(-3)时,残余黏聚力随初始饱和度增加而增加,而当干密度为1.20 g·cm^(-3)时则表现出先增后减的规律。对于两种干密度的滑带土,残余摩擦角均随初始饱和度增加而减小。低干密度条件下残余强度参数随初始饱和度的变化更敏感。

Modelling of the variation of granular base materials resilient modulus with material characteristics and humidity conditions

This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.

川南长宁地区奥陶系五峰组—志留系龙马溪组页岩气储层低电阻率响应特征及主控因素

以川南长宁地区NX22井五峰组—龙马溪组低电阻率页岩气储层为例,利用岩心矿物组分、扫描电镜、总有机碳(TOC)含量、含水饱和度测试及测井曲线等资料,确立了低电阻率页岩气储层岩石体积物理模型,采用随机法构建了三维数字岩心模型,进而利用有限元数值模拟方法模拟计算各矿物组分含量、含水饱和度及有机质石墨化的电阻率响应特征,并分析其主控因素。研究结果表明:(1)长宁地区五峰组—龙马溪组低电阻率页岩气储层岩石体积物理模型由骨架(石英、长石、方解石和白云石等)、黏土矿物、黄铁矿、未石墨化有机质以及石墨化有机质、孔隙6个部分组成。(2)三维数字岩心模型的长、宽、高分别为100×100×100像素,融入了上述物理模型中的6个部分,并采用不同的颜色对导电组分进行标识,可以显示不同方向上的切片,表征低电阻率页岩气储层的组分特性。(3)黏土矿物含量、黄铁矿含量、含水饱和度以及有机质石墨化程度等4个参数增大都会造成页岩气储层的电阻率下降,而有机质的高石墨化程度(25%)和高含水饱和度(88.0%)使页岩气储层的电阻率从正常电阻率(大于15Ω·m)降到低阻甚至超低阻(小于5Ω·m),是导致研究区页岩气储层超低阻响应的2个核心因素。

马岭油田S区延10储层特征及水驱规律研究

马岭油田S区块已进入注水开发的中高含水期,研究其水驱规律对后续改善注水开发效果具有实际意义。以S区延10_(1)^(2-1)层段为研究对象,以区域构造背景及构造特征为基础,从岩心资料、测井数据着手,重点分析沉积微相与砂体平面展布特征,总结储层物性,分析储层非均质性特征。结合油田生产资料,从非均质性方面重点分析延10储层平面、纵向水驱规律。结果表明:受储层渗透率非均质的影响,纵向上的水驱呈现复合韵律的特点,高渗透率部位水洗程度高,剩余油含油饱和度较低;较低渗透率部位水洗程度较低,含油饱和度相对较高。油层在纵向上的产液量、产水量、含水率同样呈复合韵律特点。平面上的水驱呈现出沿砂体延伸方向推进较快,主流线方向上的油井见效快。位于负向构造部位的油井较早见水,进入水量多,油层水洗较为充分;位于正向构造部位的油井注入水进入较晚,进入水量较少,水洗程度相对较低。注入水优先沿高渗透带方向推进,该方向水推较快,吸水较多。

基于微纳米CT技术的化学驱后微观剩余油定量描述

利用微纳米CT技术及室内岩心驱油实验,对岩心微观孔隙结构进行三维重构,研究水驱后和化学驱后微观剩余油的分布特征、赋存状态,定量描述不同尺寸孔隙内微观剩余油饱和度,明确不同驱油体系对微观剩余油的动用程度。结果表明:水驱后转聚合物驱的剩余油饱和度为22.3%,水驱后转二元复合驱的剩余油饱和度为18.4%,水驱后转非均相复合驱提高采收率效果明显,最终剩余油饱和度为12%。经三维重构后可以直观地看到不同驱油体系后微观剩余油的分布特征。化学驱后不同孔径内的剩余油饱和度均有所降低,大于25μm孔径内的剩余油动用效果明显,聚合物驱动用程度为66.7%.二元复合驱动用程度为75.7%、非均相复合驱动用程度为85.5%。聚合物驱和二元复合驱对孔径5μm以下孔隙内的剩余油动用程度较低,分别只有19.3%和35.9%;非均相复合驱对小于5μm孔径内的剩余油动用程度达到52.5%。非均相复合体系具有扩大波及体积和降低界面张力的双重作用。

氢化丁腈橡胶耐盐酸性能的研究

研究丙烯腈含量、饱和度和硫化体系对氢化丁腈橡胶(HNBR)硫化胶耐盐酸性能的影响。结果表明:不同牌号HNBR硫化胶经过耐盐酸试验后,均呈硬度和体积增大、拉伸强度和拉断伸长率减小的趋势;丙烯腈含量较小、饱和度较低的HNBR硫化胶的耐盐酸性能更好;与采用过氧化物硫化体系的HNBR硫化胶相比,采用硫黄硫化体系的HNBR硫化胶的耐盐酸性能更好。

Law of nonlinear flow in saturated clays and radial consolidation

It was derived that micro-scale amount level of average pore radius of clay changed from 0.01 to 0.1 micron by an equivalent concept of flow in porous media. There is good agreement between the derived results and test ones. Results of experiments show that flow in micro-scale pore of saturated clays follows law of nonlinear flow. Theoretical analyses demonstrate that an interaction of solid-liquid interfaces varies inversely with permeability or porous radius. The interaction is an important reason why nonlinear flow in saturated clays occurs. An exact mathematical model was presented for nonlinear flow in micro-scale pore of saturated clays. Dimension and physical meanings of parameters of it are definite. A new law of nonlinear flow in saturated clays was established. It can describe characteristics of flow curve of the whole process of the nonlinear flow from low hydraulic gradient to high one. Darcy law is a special case of the new law. A math- ematical model was presented for consolidation of nonlinear flow in radius direction in saturated clays with constant rate based on the new law of nonlinear flow. Equations of average mass conservation and moving boundary, and formula of excess pore pressure distribution and average degree of consolidation for nonlinear flow in saturated clay were derived by using an idea of viscous boundary layer, a method of steady state in stead of transient state and a method of integral of an equation. Laws of excess pore pressure distribution and changes of average degree of consolidation with time were obtained. Re- sults show that velocity of moving boundary decreases because of the nonlinear flow in saturated clay. The results can provide geology engineering and geotechnical engineering of saturated clay with new scientific bases. Calculations of average degree of consolidation of the Darcy flow are a special case of that of the nonlinear flow.

A Flexible Model for Moisture-Suction Relationship for Unsaturated Soils and Its Application

The mathematical equation for the moisture-suction relationship also known as soil water characteristic curve (SWCC) is one of the constitutive relations necessary for the computational modeling of deformation and flow problems of unsaturated soil using the finite element method. In this paper, a new empirical equa-tion for the SWCC is developed that incorporates the actual airentry suction and the maximum possible suction of the soil as input parameters. The capability of the new model is investigated by fitting the experimental data for twelve different soils that includes sands, silts, and clays. The model fits the experimental data well including in high suction range which is one of the difficulties observed in other commonly used models such as the Brooks and Corey, van Genuchten, and Fredlund and Xing models. The numerical stability and the performance of the new model at low and high degrees of saturations in finite element simulation are investigated by simulating the dynamic response of a compacted embankment and the results are compared with similar predictions made using widely used SWCC models.

Relationship of Resistivity with Water Content and Fissures of Unsaturated Expansive Soils

The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can be calculated from the resistivity of the liquid phase. On this basis,the two-part model of resistivity changing with the water saturation of the expansive soil can be deduced. A 2-D resistance grid model is established based on simulating the resistance of ver-tically developed fissures. Variation in measured resistance of vertically developed fissures at different positions can be calculated from this model. Fissure development can be inversely determined from the variation in the measured resis-tance. Finally,the model is verified by an indoor resistivity test for remolded soil samples,indicating that the test result agrees well with that of the model established.

Influence of specimen uniformity on mechanical behaviour of unsaturated soil

Pressure plate instrument is employed during drying, and unconfined compressive strength test is performed on the unsaturated specimen. Curves of shear force versus shear displacement, and curves of saturation degree versus time are investigated. The results show that the specimens with similar curves of saturation degree versus time have nearly identical mechanical behavior. In particular, the uniform specimens should be chosen within the lower equilibrium saturation degree because steady test results are presented. Further, the conclusion is verified by the repeated test. Thus, the method for distinguishing the uniform unsaturated specimen is obtained. In the light of the method, an improved test process is proposed. The uniform specimens should be chosen by this method under the specific matric suction, and then shear tests are carried out on the chosen unsaturated specimen. Namely, initial value of unsaturated soil is not zero matric suction but a specific suction.

基于饱和深度动态相量图的变压器涌流不平衡分析

为阐释高阻抗变压器三相涌流严重不平衡的产生机理,定义了可反映三相涌流不平衡特性的铁心“饱和深度”概念,并结合相量理论提出了基于饱和深度动态相量图的涌流不平衡特性分析方法。基于该方法可直观掌握变压器运行时各相铁心饱和深度随分合闸角度及时间的变化规律,从而快速辨识涌流极限不平衡的边界角度。不同分合闸角度时的数值模拟结果表明不平衡度和零序电流大小趋势基本一致,仿真和录波验证了出现涌流极限不平衡和零序电流峰值的边界角度的一致性。基于高阻抗变压器参数特征及边界角度,阐释了高阻抗变压器因原边零模涌流变大和副边环流变小两方面原因导致三相涌流严重不平衡的现象。