离子型稀土一维垂直入渗规律及最大粒径的影响试验研究

为了研究不同最大粒径离子型稀土土样对入渗规律的影响,利用自制的试验装置进行离子型稀土垂直入渗试验.水头高度恒定为 6 cm,土样最大粒径分别为 2.36 mm、1.18 mm、0.6 mm 和 0.3 mm. 在试验结果的基础上,利用改进的 Green-Ampt 模型分析离子型稀土入渗的饱和导水率和基质吸力. 结果表明,随着入渗时间的递增,累积入渗深度和湿润锋运移速率分别呈 “快速增加-缓慢发展 ”和 “快速减小-缓慢发展”的趋势.湿润锋运移速率与入渗时间之间满足幂函数关系,土样最大粒径对幂函数参数有较大影响.入渗率与湿润锋倒数之间具有良好的线性相关性.随着土样最大粒径的增加,饱和导水率和基质吸力也逐渐增加,二者与最大粒径之间呈指数函数关系.      

含硫充填体膨胀裂隙发育特性与单轴抗压强度的关联分析

含硫胶结充填体随着养护龄期的延长会出现膨胀开裂现象，存在明显裂隙的充填体试件再进行单轴抗压强度测试其结果十分离散，已不能有效地获得充填体力学参数.在室内进行配比试验，采用数字图像处理技术对得到的充填体表面裂隙图像进行二值化、去噪等预处理，而后计算其分形维数并分析其演化规律，且将分形维数与单轴抗压强度关联分析.研究结果表明:充填体试件面表的裂隙存在自相似性，表面裂隙越发育，其分形维数越大；分形维数与单轴抗压强度存在负相关关系，分形维数越小，其单轴抗压强度越高；分形维数可判别含硫充填体试件的完整性，当充填体表面裂隙的分形维数小于某阈值时，强度试验的结果更为可靠.      

含水率对重塑红黏土反复抗剪强度影响试验研究

红黏土性质的稳定与安全生产息息相关,抗剪强度作为红黏土强度特性之一,与红黏土的稳定性密切相关。为探究含水率对红黏土反复抗剪强度的影响,以山西长治地区的重塑红黏土为研究对象进行反复直剪试验。试验结果表明：无竖向压力时,随着剪切次数的增加,抗剪强度减小并趋于稳定值,第2次剪切达到抗剪强度时对应的剪切位移小于第1次剪切时的位移,稳定剪切时对应的剪切位移大于第1次剪切时的位移;抗剪强度与含水率呈负线性关系,且抗剪强度为土体的真黏聚力,随着含水率的增加先增大后减小。当施加竖向压力后,抗剪强度随着含水率的增加而减小;利用抗剪强度表达式拟合得到内摩擦角和黏聚力,其中黏聚力随着含水率的增加先减小后增大;通过真黏聚力计算得出新的内摩擦角,2种分析方法得出的内摩擦角基本接近且均随着含水率的增加而减小,减小幅度逐渐增大。定义黏聚力差异指数比来研究真黏聚力与黏聚力之间的差异,分析得到黏聚力与真黏聚力的差异指数比在0.75~9.96之间,当含水率为19.5%时黏聚力差异指数比达到最小。利用所建立的相关经验公式,能够为红黏土地区矿山岩土勘察、设计和开挖过程中土性参数的合理选取提供一定参考。     

单轴压缩下不同尺寸充填体能量损伤演化特征试验研究

对4种不同尺寸（40,70.7,100,150 mm）的充填体试件进行了室内单轴压缩试验,研究了尺寸变化对充填体能量演化规律和损伤破坏机制的影响,并得到了基于弹性能耗比的充填体破坏前兆判据。研究结果表明：单轴压缩下不同尺寸充填体的能量演化规律相似,体现为峰前以弹性应变能积蓄为主,峰后耗散能占比不断上升并迅速超越弹性应变能;随着试件尺寸的增加,充填体在峰值应力处总输入应变能、弹性应变能和耗散能均呈非线性下降趋势;根据耗散能曲线,可将充填体能量损伤演化过程划分为初始损伤、损伤加速、损伤稳定发展和损伤破坏4个阶段;试件尺寸越大,弹性能耗比K值变化幅度越大;弹性能耗比K值曲线整体先上升后下降,持续到一个较低值,在临近峰值应力处再转为上升。弹性能耗比K值曲线的这一变化规律可作为充填体临界破坏前兆特征。     

Engineering Properties of Lunar Soil Simulant JSC-1A

This study was carried out to assess the tensile and shear strength in lunar soil, and to examine the variation as a function of density and confinement. Geotechnical engineering properties of the lunar soil simulant designated Johnson Space Center Number One-A lunar soil simulant (JSC-1A) have been investigated experimentally. To better understand these soil properties, a variety of conventional and unconventional experiments were conducted on JSC-1A to determine its grain-size distribution, cohesion, friction angle, dilatancy angle, tensile strength, and appropriate low strain elastic constants. These experiments were conducted on JSC-1A at a variety of densities prepared through tamping densification to quantify the response of the soil over a range of conditions. To simulate lunar conditions, the samples were prepared at medium to very high relative densities. Grain-size distribution, shear strength, tensile strength, dilatancy angles, and elasticity modulus of the JSC-1A were compared with lunar soil and other simulants.     

A fractal model for cavity damage and fracture of materials during superplastic deformation

A fractal model for cavity damage and fracture of materials during superplastic deformation is proposed in this paper. The formula which shows the effect of gauge dimensions and grain size on total superplastic elongation was inferred. The formula shows that the finer the grain size, the larger the elongation of specimen and a larger elongation can be obtained by increasing the gauge width and thickness or by decreasing the gauge length of specimen under the same deformation condition. The prediction of the new formula is consistent with most experimental results observed up to now.     

Suction-Monitored Direct Shear Testing of Residual Soils from Landslide-Prone Areas

The apparent cohesion due to soil suction plays an important role in maintaining the stability of steep unsaturated soil slopes with deep ground water table. In this paper, a modified direct shear box is used to determine the relationships between the value of this additional cohesion and the associated soil suction. The apparatus incorporates a miniature tensiometer which allows for the simple and direct measurement of suction during shearing. The soil-water characteristic curves and shearing behavior of intact residual soils, being low-to-medium plasticity silts, as well as silty sand, taken from four landslide-prone areas in Thailand, have been investigated. The relatively low air-entry suctions (0–7 kPa) and bimodality of the soil-water characteristic curves gives an indication of the structured pore size distribution of the materials tested. Samples with higher suction tend to display stronger bonding at particle contacts and thus are more brittle. The shear strength is found to increase nonlinearly with suction, though linearization can be reasonably assumed for suction below around 30 kPa. Prediction of shear strength based on soil-water characteristic curves agrees better with ultimate than peak values. A simple equation is proposed for the minimum ultimate strength that can be expected in an unsaturated residual soil with a suction lower than about 30 kPa.     

六棱柱作细磨介质下磨矿能耗与粒度分布特征

六棱柱是一种面接触为主的磨矿介质.以1.18~2.0 mm、0.6~1.18 mm、0.3~0.6 mm 3个粒级样以及实际生产二段沉砂样为研究对象，分别采用等质量的六棱柱和钢锻进行分批次磨矿试验，分析了其磨矿产品的粒度分布和磨矿能耗分布特征，比表面积和体积密度与能耗和t₁₀之间的关系.试验结果表明，六棱柱作为细磨介质，与钢锻相比，磨矿产品也相同的粒度分布规律，符合JK粒度破碎模型.在相同磨矿条件下，六棱柱磨矿生产能力比不上钢锻和钢球.但给料粒度变小，六棱柱磨矿产品中P₈₀和t₁₀值与钢锻的差异也变得越来越小.与此同时，磨矿产品中合格粒级的含量高于钢锻，磨矿的能耗用于矿物的磨细，生成了更多的表面积，矿物的比表面积和能耗关系与磨矿细度与能耗的规律一致，此外矿物的体积密度随着磨矿能耗增加而递减.对于脆性矿物磨矿而言，六棱柱又是比钢锻更加优良的一种细磨介质.      

Laboratory Study of Loose Saturated and Unsaturated Decomposed Granitic Soil

Weathered soils are used extensively as fill materials in slope construction in tropical and subtropical cities such as Hong Kong. The mechanical behavior of loose decomposed fill materials, particularly in the unsaturated state, has not often been investigated and is not yet fully understood. The objective of this study was to understand the mechanical behavior of loose unsaturated decomposed granitic soil and to study the effects of the stress state, the stress path and the soil suction on the stress–strain relationship, shear strength, volume change, and dilatancy via three series of stress path triaxial tests on both saturated and unsaturated specimens. It was found that loose and saturated decomposed granitic soil behaves like clean sands during undrained shearing. Strain-softening behavior is observed in loose saturated specimens. In unsaturated specimens sheared at a constant water content, a hardening stress–strain relationship and volumetric contractions are observed in the considered range of net mean stresses. The suction of the soil contributed little to the apparent cohesion. The angle of friction appeared to be independent of the suction. In unsaturated specimens subjected to continuous wetting (suction reduction) at a constant deviator stress, the volumetric behavior changed from dilative to contractive with increasing net mean stress and the specimen failed at a degree of saturation far below full saturation. It was revealed that the dilatancy of the unsaturated soil depends on the suction, the state, and the stress path.     

渗流作用下稀土矿孔隙结构与强度弱化关系研究

为研究纯水入渗过程中重塑稀土试样微观孔隙结构和强度的变化规律,进行了室内模拟浸矿、核磁共振和三轴压缩试验。结果表明：随着纯水渗流浸矿时间的推移,试样内部微观结构的变化呈现中等孔径孔隙向大孔径孔隙变化的趋势;2个主要强度指标值即黏聚力和内摩擦角随纯水入渗时间推移呈现大幅减小的变化规律。综合分析结果表明,渗流作用使矿体内部孔隙结构发生改变从而诱发矿体强度逐步弱化;孔隙结构的变化是造成矿体强度弱化的主要诱因。     

不同氧化镁含量烧结矿粒度分布的分形研究

通过对不同MgO含量烧结矿破碎体的筛上、筛下物分布规律的研究,计算得出了烧结矿粒度分布的分形维数,线性相关系数均大于0.97,说明使用分形维数定量表征烧结矿在不同MgO含量条件下的粒度组成是可行的.结果表明:分形维数随着MgO含量的增加而增加,在一定程度上可以定量估测烧结矿中MgO含量的范围,并结合微观结构,合理解释了转鼓强度、成品率和分形维数之间的关系.为更加深入表达不同MgO含量的烧结矿的有关数值模型提供了新的理论依据和研究方法.     

南方离子型稀土一维水平入渗规律试验研究

离子型稀土原地浸矿工艺中浸矿液入渗直接影响稀土资源的高效开采与利用.基于自制试验装置进行离子型稀土一维水平入渗试验,溶浸液选取3 %硫酸铵溶液,研究了4种不同粒径稀土的累积入渗长度、湿润锋运移速率、入渗率等变化规律.结果表明:随着入渗时间的递增,累计入渗长度呈先快速增加、后缓慢发展的趋势;湿润锋运移速率和入渗率先达到最大值、后快速减小再趋于稳定,湿润锋运移速率与时间之间的关系符合幂函数关系v=λ·t-0.5;土样饱和渗透系数为0.001 3~0.002 5 cm/min,其数值随着最大粒径增大而递增,研究结果有利于实现原地浸矿的科学化.      

Retracted: Fractal Dimensions of Fracture Surfaces

Compressive strength of porous materials, especially of cement gels, has been estimated by means of fractal dimension of fracture surfaces. The relationship between mechanical strength and fractal characteristics of porous gels has been derived and tested experimentally using samples of cement gels. The dimensions of fracture surfaces have been found to be general parameters independent on the fractal dimensions of inner material components.     

Numerical Modeling of Nonhomogeneous Behavior of Structured Soils during Triaxial Tests

The nonhomogeneous behavior of structured soils during triaxial tests has been studied using a finite element model based on the Structured Cam Clay constitutive model with Biot-type consolidation. The effect of inhomogeneities caused by the end restraint is studied by simulating drained triaxial tests for samples with a height to diameter ratio of 2. It was discovered that with the increase in degree of soil structure with respect to the same soil at the reconstituted state, the inhomogeineities caused by the end restraint will increase. By loading the sample at different strain rates and assuming different hydraulic boundary conditions, inhomogeneities caused by partial drainage were investigated. It was found that if drainage is allowed from all faces of the specimen, fully drained tests can be carried out at strain rates about ten times higher than those required when the drainage is allowed only in the vertical direction at the top and bottom of the specimen, confirming the findings of previous studies. Both end restraint and partial drainage can cause bulging of the triaxial specimen around mid-height. Inhomogeneities due to partial drainage influence the stress–strain behavior during destructuring, a characteristic feature of a structured soil. With an increase in the strain rate, the change in voids ratio during destructuration reduces, but, in contrast, the mean effective stress at which destructuration commences was found to increase. It is shown that the stress–strain behavior of the soil calculated for a triaxial specimen with inhomogeneities, based on global measurements of the triaxial response, does not represent the true constitutive behavior of the soil inside the test specimen. For most soils analyzed, the deviatoric stress based on the global measurements is about 25% less than that for the soil inside the test specimen, when the applied axial strain is about 30%. Therefore it can be concluded that the conventional global measurements of the sample response may not accurately reflect the true stress–strain behavior of a structured soil. This finding has major implications for the interpretation of laboratory triaxial tests on structured soils.     

Simplified Relationships for Particle-Size Distribution and Permeation Groutability Limits for Soils

The particle-size distribution of soil with mean particle size and fines content are used not only in soil classifications but also in a number of other soil property relationships. In this study, two simple relationships (hyperbolic [tan?h(x)] and S-curve) were investigated to represent the particle size distribution of soils. The parameters of the hyperbolic model were correlated to various soil parameters such as the mean particle size, particle size range, and fines content. There was no direct correlation between Fredlund (four-parameter model) and S-curve model parameters and the soil parameters. The predictions of the two (hyperbolic) and three (S-curve) parameter models were compared to the four-parameter model (unimodal) using limited soil data from the literature and the agreements were good. The hyperbolic model was used to map the Unified Soil Classification System. A recent study had quantified the relationship between the grouting pressure and the fines content in nonplastic soils. Also in the current practice, upper and lower particle-size distribution limits are used in determining the groutability of soils. In this study, the relationship between grouting pressure and fines contents of the soil was generalized using the hyperbolic particle-size distribution model and verified with a groutability study using an acrylamide grout. Based on limited data in the literature, the groutability of soils was defined using a new set of parameters, grouting pressure, fines content, and mean particle size diameter of the soil.     

服役环境下TA2/Q235爆炸复合板剪切断口分形表征

为了定量研究服役条件下TA2/Q235爆炸焊接复合板剪切强度与断口分形维数及多重分形谱的关系,明确适合TA2/Q235复合板的最佳分形表征方法,通过热处理模拟服役过程,对服役后的样品开展剪切测试,并引入分形理论对剪切断口进行表征,建立了剪切强度与分形维数及多重分形谱的定量关系。结果表明,200、400和600℃服役后,样品剪切强度与断口多重分形谱宽度负相关;结合残余应力消除及再结晶长大对TA2/Q235爆炸复合板剪切断口形貌影响规律的分析,相比分形维数,多重分形谱能更准确地描述断口力学信息。     

New Approach to Limit Equilibrium and Reliability Analysis of Soil Nailed Walls

A new approach to the limit equilibrium method is developed and used for the analysis of soil nailed walls. The basic procedure of the new approach is to compute the interslice forces by recursion and to fulfill the equilibrium requirement for interslice forces of the last boundary slice by iteration. Reliability analysis for soil nailed walls is carried out by considering the cohesion and internal friction angle of soil as random variables. The degree of mobilization of friction resistance between the nails and surrounding soil is taken as a third random variable. A parametric study is carried out to study the effect of soil behavior and the arrangement pattern of nails on the factor of safety and reliability index. Finally, an optimization technique is employed to obtain the minimum cost design of soil nailed walls with an object function expressed by the total nail length, which is considered an appropriate measure of the total cost of a soil nailed wall.     

钢中夹杂物的分形维数及其与形貌特征的关系

 利用Matlab图像处理功能计算了钢中夹杂物SEM图像的边缘、二维和三维分形维数,并讨论了边缘分形维数与夹杂物颗粒微观凝聚机制和三维分形维数与其融入顶渣中动力学之间的关系。结果表明：边缘分形维数可定量地表征夹杂物边界轮廓线的曲折复杂程度;对非润湿夹杂物颗粒来说,其边缘分形维数越大,表明气泡易于在其表面生成,从而更加有力于夹杂物的碰撞凝聚长大;夹杂物颗粒的三维分形维数越小,更有利于夹杂物融入渣中而被去除;分形维数是一个影响不规则夹杂物颗粒碰撞、凝聚和去除的重要参数。     

硫酸盐侵蚀作用下纤维锂渣混凝土裂缝的分形特征

为探究新型混凝土受硫酸盐侵蚀后的力学性能,采用质量分数为5%的硫酸盐溶液全浸泡加速侵蚀法,对11组聚丙烯纤维混凝土（PC）试块、11组聚丙烯纤维锂渣混凝土（PLiC）试块、8根PC大偏心受压柱和8根PLiC大偏心受压柱进行侵蚀试验,得到了不同侵蚀时间下混凝土的力学性能。基于分形理论分析了试块及构件破坏时表面裂缝分布的分形特征,详细讨论了试块及构件表面裂缝分形维数与其侵蚀时间、抗压强度、极限承载力之间的关系。研究表明,PC和PLiC立方体抗压强度随侵蚀天数先增加后降低,在120 d达到最大;试块及构件破坏时表面裂缝分布具有分形特征,试块表面裂缝分形维数随侵蚀天数的增加呈现先增加后减少再增加的规律,随试块抗压强度的提高而减少;PC及PLiC混凝土大偏心柱极限承载力随侵蚀天数的增加先增加后减少,锂渣的掺入可以提高聚丙烯纤维混凝土柱的抗硫酸盐侵蚀能力,构件破坏时表面裂缝分形维数随硫酸盐侵蚀天数呈现震荡上升的趋势;因此混凝土表面裂缝的分形特征可作为判定构件损伤程度的指标之一,可为今后对在役混凝土结构承载力和寿命预测提供参考。