A survey of the physical properties of some carbonate rocks

Samples were taken from the Carboniferous Limestone, the Magnesian Limestone, the Inferior Oolitic Limestone and the Great Oolitic Limestone. Their specific gravities, dry and saturated densities were determined, as were their absolute and effective porosities. The densities decreased and porosities increased with decreasing age of the limestone concerned. The permeability of these samples increased as the porosity increased. Furthermore the strength decreased with increasing porosity, that is, the Carboniferous Limestone was very strong whereas the Great Oolitic Limestone was moderately weak. When saturated the strongest limestone showed the least percentage reduction in strength. The strongest limestone also possessed the highest values of hardness, the weakest having the lowest values. As far as Young's modulus was concerned it tended to increase as density, strength and hardness increased. The Carboniferous Limestone recorded the highest values of Young's modulus, the Great Oolitic Limestone the lowest. Poisson's ratio and related elastic properties were also determined.     

Determination of the thermal conductivity from physico-mechanical properties

Samples of limestone, dolomite, dolomitic limestone, marble, travertine, sandstone, siltstone, andesite, basalt and porous basalt from different parts of Turkey were tested to obtain their UCS, porosity, water absorption, density, P-wave velocity and thermal conductivity (TC). It was observed that while TC increased with density, P-wave velocity and UCS, it decreased with increasing porosity. Equations are presented to allow an assessment of TC from these physico-mechanical properties.      

Water absorption and dehydration of natural stones versus time

Physical, chemical and mechanical properties of natural stones play an important role on deciding their application area as a building stone. In this study, water absorption and dehydration time of five different types of natural stones (marble, limestone, travertine, onyx and granite) were comparatively examined. Porosity, dry unit weight, wet unit weight, water absorption ratio and chemical analyses of the rock samples were also determined. In the light of the obtained experimental results, it was found that MgO content as the chemical property, and porosity as the physical property played a major role in the water absorption capacity and dehydration time of the studied natural stones. Basing on some observations made in this study, it was also emphasized that common standards involving the determination of water absorption coefficient by the capillarity test in rocks should be re-evaluated.     

Weathering and its relation to geomechanical properties of Cavusbasi granitic rocks in northwestern Turkey

The effect of mainly mechanical weathering on the granodiorites, granites and quartz diorites of the Cavusbasi area of northwest Turkey are described, the samples having been taken from cores and field exposures. The primary characteristics of these rocks are affected by the weathering process which results in a significant constraint on their use in engineering works. The tests undertaken on samples in the various weathering grades included point load and uniaxial compressive strength, slake durability, porosity, loss on ignition, dry and saturated unit weight and water absorption. A tentative correlation between these properties is presented. Electronic Publication     

Effect of aggregate type on properties of hardened self-consolidating lightweight concrete (SCLC)

In this study, the effects of aggregate type on the physical and mechanical properties of hardened self-consolidating concrete produced with lightweight aggregate (SCLC) were investigated. In experiments, three coarse lightweight aggregate (LWA) types, pumice, volcanic tuff and diatomite, and normal limestone aggregate were used. Different combinations of water to binder ratio and superplasticizer dosage levels were prepared for the SCLC mixtures. The total powder content (cement and mineral additives) was constant in the experiments. Physical properties such as thermal conductivity, dry unit weight, porosity and capillarity; mechanical properties such as compressive and splitting tensile strength, modulus of elasticity and abrasion resistance were determined in hardened condition. The results, in general, showed that SCLC with LWA in lower unit weight has lower mechanical and physical properties except for thermal properties when compared to properties of SCC.     

Influence of petrographic characteristics on physico-mechanical properties of ultrabasic rocks from central Greece

Ultrabasic rocks show a variety of engineering properties that may affect quarrying operations, tunnelling, mining, slope stability and the use of rock as a construction material. The physico-mechanical properties are influenced by the mineralogical and textural characteristics as well as the weathering of the rock. For this reason, the relationships between petrographic and physico-mechanical properties of fresh (peridotites) and serpentinized (serpentinites) ultrabasic rocks from central Greece, were investigated using correlation analysis. Thin sections, from the 47 samples, were prepared and examined under the polarizing microscope with the aim of describing the main mineralogical composition, the grain size, the serpentinization percentage and the structure of the rocks. The mineralogical and textural characteristics of some of them were also studied by X-ray diffraction analyses and the scanning electron microscope. The 47 samples were tested to determine dry and saturated unit weight, effective porosity, uniaxial compressive strength and static modulus of elasticity. The relationships between these properties and the petrographic characteristics are described by simple regression analyses. The research demonstrates that the physico-mechanical characteristics are strongly influenced by the petrographic characteristics except for mineral grain size. Negative linear correlations exist between serpentinization percentage and dry unit weight, while the effective porosity has a strong positive relationship with degree of serpentinization. Positive relationships are also obtained between the mechanical properties and dry unit weight and micropetrographic index I _ps, while the increase of effective porosity causes a decrease in the index I _ps (logarithmically in peridotites, and exponentially in serpentinites). The mechanical properties are exponentially related (negatively) to the serpentinization percentage in serpentinites and logarithmically (negatively) in peridotites. The serpentine plays a very important role in strength and elasticity modulus reduction, while the primary minerals have a smaller effect on the mechanical properties.     

Correlation between slake durability and rock properties for some carbonate rocks

The paper reports a study to assess the relationship between slake durability indices and uniaxial compressive strength, Schmidt hardness, P-wave velocity, modulus of elasticity, effective porosity, water absorption and dry and saturated unit weight for seven types of carbonate rocks obtained from south west Turkey. It was found that the dry unit weight, saturated unit weight and Schmidt hardness gave the best relationship with first cycle slake durability (r = 0.99) while uniaxial compressive strength has a strong relationship with fourth cycle slake durability (r = 0.94). The results showed little difference in the correlation coefficients obtained after the fourth cycle. It is concluded that, for the rocks studied, the first and fourth cycles provide sufficiently good data on the durability for preliminary engineering/design works and that the second to fourth cycle results could be estimated using the first cycle slake durability index (r = 0.99–0.97).     

Dynamic mechanical behavior of some carbonate rocks

The effects of porosity, unit volume weight and Schmidt hardness on the quasi-static and dynamic compressive behaviors of some carbonate rocks were investigated using classical servo-hydraulic testing machine and split Hopkinson pressure bar (SHPB) testing system, respectively. For dynamic compression testing, cylindrical samples 18 mm in diameter and 11 mm long were obtained from rock samples of light and dark travertines, lymra and beige marbles. For quasi-static compression testing, cylindrical samples were prepared according to the International Society for Rock Mechanics (ISRM) standards. The results of the physical and mechanical properties of the rock samples have shown that the porosity, unit volume weight and Schmidt hardness, have significant effects on the compressive stress–strain behavior of the rock samples under dynamic loading. The results have also shown that the beige limestone samples have significantly higher dynamic compressive strength than the other carbonate rock samples.     

Compaction of granular calcite by pressure solution at room temperature and effects of pore fluid chemistry

Pressure solution is an efficient compaction mechanism leading to porosity/permeability reduction in both clastic and carbonate rocks. We performed compaction experiments on crushed limestone and granular calcite at room temperature and 1–4 MPa effective stress using various pore fluids. By applying a dry pre-compaction at 8 MPa, we could largely eliminate deformation mechanisms such as grain rearrangement, sliding and fracturing from runs employing a pore fluid. Compaction creep occurred only in samples filled with a saturated carbonate solution, in contrast to those filled with chemically inert fluids, at . The measured strain rates increased with decreasing grain size and with increasing effective stress according to power laws with exponents of about 3 and 1–2, respectively. Samples made from naturally oil-contaminated limestone showed far less compaction than oil-free samples. Addition of dissolution and precipitation inhibitors (magnesium and phosphate ions) to the pore fluid significantly decreased compaction rates of wet samples, indicating that creep must have involved calcite dissolution/precipitation. Pore fluid with a salinity (NaCl) of 0.1–0.5 mole/l increased the compaction strain rate compared to non-saline solutions. The experimental results suggest the main deformation mechanism in calcite under our experimental conditions was pressure solution and that diffusion is likely to be the rate-controlling process in pure solution system.     

Water-induced variations in mechanical properties of clay-bearing rocks

This study presents the results obtained from laboratory tests carried out on different types of clay-bearing rock collected from various parts of Turkey, to quantify the effects of water content on mechanical properties of the rocks, and to develop a method for estimating the rock strength and deformability at any water content based on physical properties. For this purpose, in addition to physical properties of the rock types collected, needle penetration resistance, uniaxial compressive strength, tensile strength and modulus of elasticity were determined on a number of specimens with different water contents. The results suggest that with increasing the water content the reductions in the uniaxial compressive strength, modulus of elasticity and tensile strength are up to 90%, 93% and 90%, respectively, from oven-dried to saturated conditions. Based on a series of empirical models developed and the comparisons between the experimentally determined mechanical properties and those predicted from the models, it is concluded that the suggested models seem to be very practical tools to estimate the mechanical properties of the clay-bearing rocks at any water content using the coefficients related to some physical properties of the rock material such as dry unit weight, water absorption by weight and porosity. In addition, needle penetration test is particularly suitable for such rocks to indirectly estimate their uniaxial compressive strength.     

Indentation hardness test to estimate the sawability of carbonate rocks

The performance of large-diameter circular saws on eight carbonate rocks was recorded and indentation hardness, density and porosity tests were undertaken on the five travertines, two limestone and one dolomitic limestone samples returned to the laboratory. A strong linear correlation between indentation hardness index values and the hourly production of the circular saws was found. The slab production was slowest for the dolomitic limestone rocks with the highest indentation hardness, lowest porosity and highest density values.      

表面形貌对岩石摩擦滑动本构参数影响研究

 对典型岩石摩擦滑动试验装置进行改进,以千枚岩、石英岩、石英砂岩、岩屑砂岩、大理岩、石灰岩、鲕状石灰岩和白云质灰岩等岩样作为研究对象,以其抛光面作为摩擦滑动面,从本构参数的角度出发,研究自然、饱水和干燥状态下岩石摩擦滑动过程中的稳定性。采用R-D本构模型分析不同状态下岩石的摩擦滑动本构参数,基于岩石抛光表面形貌分析微凸体和分形维数对岩石摩擦滑动本构参数的影响。试验结果表明：在相同抛光条件下,不同岩石滑动表面微凸体的直径均值、高度均值和表面轮廓平均高度不同,随着这3个参数的增加,本构参数均呈线性规律降低;滑动表面形貌越精细分形维数越大,随着分形维数的增加,本构参数呈线性规律增加。     

Effect of soil compaction conditions on geomembrane-soil interface strength

A laboratory investigation was recently undertaken to evaluate the shear strength of the interface between a cohesive soil used for linear construction and a high-density polyethylene (HDPE) geomembrane. In the investigation, the interface shear strength was measured in a direct shear apparatus. The compaction water content and dry unit weight of the soil were varied in each test. It was found that the shear strength of the interface between these two materials is strongly affected by the compaction water content and dry unit weight of the soil. It is concluded from the test results that the soil compaction conditions strongly influenced the interface shear strength and this factor, among other, should be carefully considered during design.     

Use of diatomite as partial replacement for Portland cement in cement mortars

The aim of the present study is to investigate the use of diatomite as a partial replacement for cement in the production of cement mortar. Diatomite was used at 0%, 5%, 10% and 15% replacement by weight for cement while sand and water quantities were kept constant. Compressive and flexural strength, freeze–thaw resistance, sulfate resistance, water absorption and dry unit weight of the mortars were determined. The compressive and flexural strength decreased with increasing diatomite content for all curing periods. However the compressive strength of the cement mortar which was produced with 5% diatomite content complied with the minimum specified value of given in the standards. Diatomite replacement generally increased the compressive strength of the cement mortar after 25 freezing and thawing cycles. Water absorption of the mortars decreased with the increase of diatomite content except the mortar containing of 15% diatomite. Dry unit weight of the cement mortar was lower than the control mortar because of high porosity of diatomite. The expansion of the cement mortar bars immersed in 5% sodium sulfate solution decreased with increasing diatomite content and generally the sulfate resistance of the mortars was higher than that of the control mortar.     

The using of waste phosphogypsum and natural gypsum in adobe stabilization

The best known disadvantages of adobe are its low mechanical properties and poor resistance to water damage. In this research waste phosphogypsum (PG) and natural gypsum were used as stabilization material to improve the properties of adobe soil and to reduce its disadvantages at least partially. The compressive and flexural strength, softening in water, drying shrinkage and unit weight values were determined on adobe samples. The strength values of adobe samples increased with both gypsum additions. The most resistance of the adobe samples against softening in water was obtained with 25% PG addition. Drying shrinkage of test samples reduced with increasing PG content. The dry unit weight of the specimens was not in the recommended range specified in the standards. Test results showed that PG can be used as alternative material in adobe stabilization to bring economy and to reduce environmental pollution.     

Predicting the physico-mechanical properties of rocks from electrical impedance spectroscopy measurements

Electrical resistivity values of eight different samples cored from a fault breccia were measured using an impedance analyser. The uniaxial compressive strength, elastic modulus, point load strength, Schmidt hammer value, P-wave velocity, density and porosity values of the samples were determined in the laboratory. Electrical resistivity values were correlated with the corresponding physico-mechanical properties using the method of least-squares regression and the derived equations were checked by the t and F-test. A strong logarithmic relation between uniaxial compressive strength and resistivity was found. The relation between elastic modulus and resistivity is significant and follows a logarithmic function. Density was linearly, and porosity was exponentially correlated with resistivity.It may be concluded that electrical resistivity can be used as a representative measure of rock properties, particularly for characterizing rocks for which regularly shaped specimen are difficult to obtain. However, the effect of different rock types on the correlations must be further investigated. Additionally, the effect of certain minerals on the rock's resistivity must be taken into account, especially when testing dry or partially saturated rocks.     

Laboratory studies of electrical potential during rock failure

We have investigated electrical potential and acoustic emissions signals associated with rock deformation. Five rock types were studied; Clashach, Bentheim and Darley Dale sandstones (all quartz-rich) and a Seljadur basalt and Portland limestone (both quartz-free), both air dry and the rocks were tested in distilled water. Shallow crustal conditions were simulated in a triaxial rock deformation cell with a confining pressure simulating depth of 40 MPa, pore pressures ranging 5–35 MPa, and strain rates 10⁻⁷–10⁻⁴ s⁻¹. Precursory electric potential signals prior to failure were observed in both saturated and dry samples of the quartz-rich sandstones, but only observed in the water saturated quartz-free rocks. Co-seismic electrical signals were obtained in all tests, providing strong evidence that two of the main sources for precursory and co-seismic signals are the piezoelectric and electrokinetic phenomena. Lowering the strain rate resulted in an increase in the number of acoustic emissions. The pore volume changes during compaction and dilatancy remained approximately constant for all strain rates. Streaming potential generated by fluid flow across the sample was also measured at different stages of deformation. The potential signals increased with the pore pressure gradient.     

考虑垃圾体成层性的渗滤液回灌运移规律

渗滤液回灌不仅能处理渗滤液、节约费用和保护环境,而且加速了填埋场稳定化,增加了产气率。以上海某填埋场四期工程为计算模型,本文考虑垃圾土沉降导致的成层性,运用SEEP/W有限元软件模拟渗滤液喷洒回灌。垃圾土在自重作用下会产生较大的沉降变形,导致垃圾土的孔隙率随深度变化,残余含水量、饱和含水量及饱和渗透系数也随之变化。在数值模拟中,以VGM(van-Genuchten-Mualem)函数描述垃圾土渗透系数与基质吸力关系,以流量边界模拟填埋场顶部、底部的渗滤液回灌和导排,分析了回灌过程中渗滤液的饱和-非饱和渗流情况,进而探讨了垃圾土成层性、回灌强度和排水流量对渗滤液运移规律的影响。     

饱水过程中类岩石材料波速和电阻率变化规律及其相互关系试验研究

 研究饱水过程中岩石波速和电阻率变化规律及其相互关系,对实际工程中岩石物性判断和地球物理探测资料综合分析解释具有重要意义。为防止原岩试块的矿物组成、原生裂隙等其他因素对试验结果的影响,采用水泥砂浆制作了30组孔隙率不同的类岩石材料试块,系统测试了饱水过程中不同试块的波速和电阻率变化情况,分别揭示了波速和电阻率随饱和度、孔隙率的变化规律。采用常用的基于Wood理论假设的Gassmann方程得到了波速与饱和度、孔隙率的理论关系,但与试验实测结果相比,该理论关系不能较好的描述饱水达到门槛值之后波速快速上升的特征。对此,考虑重力等影响对试块中孔隙水的分布状态做出了合理假设,修正了饱水全过程中波速与饱和度、孔隙率的关系式,与试验实测数据变化特征较一致。同时采用Archie的非饱和岩石电阻率模型公式对电阻率随饱和度和孔隙率变化规律进行了较好拟合。在此基础上,针对以往波速与电阻率关系研究中仅以孔隙率为纽带的问题,综合考虑孔隙率和饱水状态对波速-电阻率变化规律的影响,建立了以试块孔隙率和饱水状态为桥梁的波速–电阻率关系,与试验实测数据拟合较好,并通过石灰岩原岩试块测试验证了其合理性。     

单轴压缩下饱水裂隙砂岩体积效应的试验研究

为研究水和岩样体积对砂岩物理力学及变形特性的影响,采用MTS815型岩石力学测试系统,对干燥和饱水状态下的3种不同体积(高径比2∶ 1)完整和裂隙砂岩进行单轴压缩试验。结果表明:完整和裂隙砂岩的孔隙率与饱和吸水率与岩样体积成正比;干燥和饱水的完整与裂隙砂岩单轴抗压强度均随体积增大而小幅降低;砂岩弹性模量和变形模量与岩样体积呈负相关,且水降低了砂岩的弹性模量与变形模量;干燥砂岩的泊松比随岩样体积增加而增大,而饱水砂岩则随岩样体积先增加,后稳定;干燥的完整和裂隙砂岩的宏观破坏形式由小尺寸的轴向多劈裂面破坏逐渐转变为大尺寸的单一剪切破坏,水的存在对岩样单轴压缩破坏形态没有明显影响。