Influence of manufactured sand characteristics on strength and abrasion resistance of pavement cement concrete

Manufactured sand (MS) particles are generally more angular with a rougher surface texture than river sand (RS) particles. MS can also contain significant quantities of particles smaller than 75 μm called rock microfines. This paper present results from a laboratory study on the influence of the MS characteristics, such as rock microfines content, surface roughness, crushing value and rock types of MS particles, on the strength and abrasion resistance of pavement cement concrete (PCC). Resulted show that the increment of limestone microfines amount in MS from 4.3% to 20% by mass increases the compressive and flexural strengths and improves the abrasion resistance of the MS-PCC. The MS-PCC has higher compressive and flexural strengths when the surface roughness of the sand particles is larger and the crushing value is lower. The abrasion resistance of MS-PCC is improved with the increment of surface roughness and deceases of crushing value and Los Angeles abrasion value of sand particles, while has not evident relation with the silicon content of sand.     

A field index to determine the strength characteristics of crushed aggregate

The suitability of a simple technique to determine the strength characteristics of aggregates is reviewed. The results indicate that the strength characteristics of aggregates – in terms of crushing, impact and abrasion values – can be estimated and predicted from simple and quick tests for rock strength such as the Schmidt hammer and point load. The rocks and aggregates used in this work were of igneous, sedimentary and metamorphic origin and of different types, ages and degrees of weathering. More than 110 rocks and aggregate samples were tested according to British Standard and ASTM. The laboratory tests included the Schmidt hammer and point load for rock material while the crushing impact and Los Angeles abrasion test were undertaken on the aggregates. Regression analyses were performed and empirical relationships between the strength of rocks (in terms of their compressive strength and point load indices) and aggregates (in terms of their crushing, impact and abrasion values) were developed. Relatively strong relationships were obtained between the compressive strength of the rock and the crushing and impact value of the aggregate, while moderately strong relationships were obtained for the Los Angeles abrasion values. Electronic Publication     

Evolution of the Sedrun landslide (Graubünden, Switzerland) with ortho-rectified air images

The slope movement at Sedrun (Switzerland) has been studied with ortho-rectified images. Displacement maps compiled for two periods (1973–1990 and 1990–2003), based on a correlation of the aerial images indicate maximum average slope movements of 60 cm/year, similar to those obtained by traditional photogrammetry over the period 1973–1990. The limits of the most active zones determined by image correlation correspond to those obtained by fieldwork. Comparison of the two displacement maps shows an acceleration of the instability of 150% since 1990. This paper demonstrates the value of using more than one technique to help understand the evolution of this long-term instability.     

Estimating the unconfined compressive strength of intact rocks from Equotip hardness

In order to utilize the Equotip hardness tester, originally developed in the field of metallic engineering, as an indirect method to predict the unconfined compressive strength (UCS) of rock, laboratory tests were undertaken to establish the UCS, Equotip hardness (L-value) and porosity of nine rock types. Using existing data from Verwaal and Mulder (Int J Rock Mech Min Sci Geomech Abstr 30:659–662, 1993) and the results of laboratory tests, an equation relating UCS (MPa) and L-value obtained from single impacts (L _s) and porosity (n %) was derived, which provides a close approximation of the UCS value. An equation to relate UCS and Equotip hardness is also presented, although this is less accurate. It is considered Equotip testing has advantages over the commonly used Schmidt hammer test.      

Requirements for accurate quantification of self-affine roughness using the roughness–length method

Self-affine fractals have the potential to represent rock joint roughness profiles. Fractional Brownian profiles (self-affine profiles) with known values of fractal dimension, D, input standard deviation, σ, and data density, d, were generated. For different values of the input parameter of the roughness–length method (window length, w), D and another associated fractal parameter A were calculated for the aforementioned profiles. The calculated D was compared with the D used for the generation to determine the accuracy of calculated D. Suitable ranges for w were estimated to produce accurate D (within ±10% error) for the generated profiles. The results showed that to obtain reliable estimates for fractal parameters of a natural rock joint profile, it is necessary to choose a unit for the profile length to satisfy a data density (d) greater than or equal to 5.1. For roughness profiles having 5.1≤d≤51.23 and 1.2≤D≤1.7, w values between 2.5% and 10% of the profile length were found to be highly suitable to produce accurate fractal parameter estimates. It is recommended to use at least seven w values between the estimated minimum and maximum suitable w values in estimating fractal parameters of a natural rock joint profile. It was found that σ and a global trend of a roughness profile have no effect on calculated D. The estimated A was found to increase with both D and σ. The parameter D captures the auto-correlation and A captures the amplitude of a roughness profile at different scales. Therefore, the parameters D and A are recommended to use with the roughness–length method in quantifying rock joint roughness. In addition, at least one more parameter is required to quantify the global trend of a roughness profile, if it exist; in many cases just the inclination or declination angle of the roughness profile in the direction considered would be sufficient to estimate the global trend. Calculated cross-over lengths (segment length of a profile at which a self-affine profile becomes self-similar) for the profiles investigated were found to be extremely small (less than 0.6% of the profile length) indicating that laser profilometers are required to make roughness measurements at interval lengths comparable to the cross-over lengths of the natural rock joint profiles. To calculate rock joint roughness parameters accurately using the self-similar techniques, it is necessary to have roughness measurements made at interval lengths comparable to the cross-over length of the profile. This indicate clearly the difficulty of using self-similar techniques such as the divider method in estimating rock joint roughness accurately.     

Deposition of aerosol particles on rough surfaces inside a test chamber

We investigated the deposition rate of aerosol particles (diameter between 0.03 and 5 μm) on rough surfaces of wallpapers, wall-plasters, and two types of carpets inside a test chamber. Compared to a smooth aluminum surface, the deposition rate of aerosol particles on the tested surfaces was up to 20 times depending on the surface roughness, mixing intensity, and particle size. A rough surface with a dimensionless surface roughness height k⁺ < 0.06 can be treated as a hydraulically smooth. The estimated deposition rates in this study and those predicted by a deposition model, which incorporates surface roughness, were in good agreement for coarse mode particles (diameter > 1 μm) when k⁺ < 1.04 and for ultrafine particles (diameter < 0.1 μm) when k⁺ < 0.48. The agreement between the model prediction and our estimation was better for coarse mode particles than for ultrafine particles. Deposition of aerosol particles, especially fine particles, needs more empirical investigations aiming at improving the existing models.     

Hydrogeological behaviour of an unsaturated waste rock pile: a case study at the Golden Sunlight Mine,Montana, USA

Parent geology, mining operation, construction practice and weathering processes govern the hydrogeological behaviour of waste rock piles. Variable heterogeneity in such earth structures requires site specific correlations. Based on field investigation and laboratory characterization, this paper developed a physical model for the unsaturated East Pile at the Golden Sunlight Mine in Montana, USA. Results indicate that the pile had interfingered dipping beds characterized by a matrix-supported structure in the fine grained layers and a clast-supported structure in the coarse grained layers. Waste rock with at least 45% sand retained water (ψ _a = 2–4 kPa, ψ _r = 20–40 kPa, k _sat = 3.5 × 10⁻³ cm/s, k _unsat = 2–3 orders of magnitude lower at 100 kPa) whereas materials with less than 45% sand drained rapidly (ψ _a < 1 kPa, ψ _r < 10 kPa, k _sat = 1 × 10⁻¹ cm/s, k _unsat > 6 orders of magnitude lower at 10 kPa).      

The 17 February 2006 Guinsaugon rock slide-debris avalanche, Southern Leyte, Philippines: deposit characteristics and failure mechanism

The Guinsaugon rock slide-debris avalanche was the most catastrophic single landslide event in Philippine history, with 14–18 M m³ of debris instantly burying an entire village. Hummocky topography, pressure ridges and other internal structures suggest that the landslide deposit was emplaced as a debris avalanche and debris flow. Susceptibility to planar and wedge failures as well as to toppling due to rock discontinuities were demonstrated using kinematic analysis and SMR. Limit equilibrium analysis on planar failures yielded factors of safety ranging from 0.8 to 1.5. The study showed that pore pressure on discontinuities had a more significant effect on the slope stability than seismicity. For wedge failures, there is a sudden drop in the factor of safety at pore water pressures of 258–306 kPa. At the site, the pore water pressure may have been as high as 490 kPa. The possibility of such a landslide event in the future is discussed.      

Mathematical model of particle penetration through smooth/rough building envelop leakages

People in China spend about 85% of their time indoor, of which residential building accounts for about 50%. Furthermore, most residential dwellings do not have mechanical ventilation systems, and air infiltrates during heating and cooling seasons. Consequently, human inhalation exposure to particles of outdoor origin depends substantially on the degree to which particles can penetrate the building envelope and remain suspended in indoor air. In this paper, the impact factors of particle penetration are analyzed, and a mathematical model is developed to simulate particle penetration through cracks with rough/smooth inner surfaces. For smooth inner surfaces, the results from the mathematical model show good agreement with the experimental data; for penetration through actual building envelop, the results from the rough surface model shows better agreement than the smooth surface model. It is observed that the roughness of the cracks plays a more important role in influencing deposition of particles with diameter d < 0.04 μm. The roughness mainly influences the Brownian diffusion mechanism of particles deposition. Discrepancies exist between two models and experimental data for particles with diameter ranging from 0.075 to 0.54 μm, which implies that inertia interception caused by roughness plays a more important role in enhancing deposition for particles in this range. The thermal property of the building shell is not an effective factor at removing infiltrated particles.     

A dilatometer for determination of the compression modulus of soils under field conditions

Conclusions 1. Use of the dilatometer reduces labor and time outlays by a factor of approximately 10–15 as compared with plate tests, and makes it possible to determine the compression modulus at a depth to 30 m. In addition to other indirect methods, this method is recommended for engineering surveys of quaternary silty-clayey soils exhibiting isotropic properties, irrespective of their genesis and consistency, 2. When the dilatometer is used for surveys, it is necessary to obtain no less than six compression-modulus determinations foe each engineering-geologic horizon to evaluate the soil's inhomogeneity, and to process them statistically to determine the average (normalized) E_d value for a coefficient of variation of not more than 0.3 in conformity with the requirements set forth in GOST 20522-75. The average value obtained is then introduced to the correlation equation corresponding to soil conditions similar to those in the surveys. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 22–25, March–April, 1990.     

Engineering evaluation of the stability of underground arched excavations

Conclusions 1. By means of the proposed method it is possible to predict different accidental overbreaks — the most characteristic manifestation of the rock pressure on the enclosing timbering under conditions of rock of medium firmness, which agrees with the underground hydraulic construction practice. The analytical dimensions of these overbreaks in accordance with this practice turn out to be, in the depth range which is characteristic for this type of construction, somewhat smaller than those predicted in the usually applied procedures and, at the same time, they are sufficiently large so that the possibility of development of such overbreaks must be taken into account in the analysis of the enclosing timbering. 2. Analyses made for arched excavations by the procedure described in this article takes account of the additional concentration and characteristics of the distribution of stresses for arched excavations in comparison with circular. Translated from Oznovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 12–14, September–October, 1990.     

Analyses of the seismic responses of soil layers with deep deposits

Several typical problems in the seismic response analysis of soil layers with deep deposits have been studied according to the seismic response analysis of the soil layer in the Shanghai region. The problems include the effect of the inclination of the bedrock under the soil layer on the seismic responses of the soil layer, the rationality of the artificial horizontal bedrock boundary in the soil layer, and the effect of the wave velocity of the bedrock and dynamic characteristics of the soil media on the seismic responses of the soil layer. Some results are obtained by numerical analysis. In the seismic response analysis, the effect of angle of inclination of the rock surface under the soil layer can be neglected if the angle is not more than two degrees. A significant error will be introduced in the calculation when the artificial horizontal rock surface is assumed in the soil layer according to the shear velocity of the soil media. The elasticity of the solid rock has little influence on the seismic response of the deep soil layer. The field investigation on the soil dynamic property should be paid more attention to. Translated from Journal of Tongji University (Natural Science), 2006, 34(4): 423–427 [译自: 同济大学学报(自然科学版)]     

Estimating the relation between surface roughness and mechanical properties of rock joints

Discontinuities in rock masses have an important influence on deformational behaviour of blocky rock systems. For a single rock joint, the roughness of its surface is of paramount importance to its mechanical and hydraulic properties, such as friction angle, shear strength, and dilatancy/aperture. Many methods have been used to characterize the surface roughness of rock joints, such as joint roughness coefficients (JRC), root mean square (RMS) value, structure function (SF) etc. However, most of these methods can only be used in the 2-D models. In this study, we carried out direct shear experiments on rock joints under both constant normal load (CNL) and constant normal stiffness (CNS) conditions, and measured the surfaces of rock joints before and after shearing, using a 3-D laser scanning profilometer system. By using a 3-D fractal evaluation method of roughness characterization, the projective covering method (PCM) and a direct shear apparatus of high accuracy, the relation between mechanical properties of rock joints under different boundary conditions and the change of their fractal dimensions in both 2-D and 3-D models have been examined, which gives a new approach to accurately evaluate the evolution of roughness of rock joint surfaces and its influence on the hydro-mechanical behaviours of rock joints.     

测定岩体变形特性的BJ-110钻孔弹模计

本文简略介绍了测定岩体变形模量的重要性和各种测试方法,古德曼千斤顶（Goodman Jack）及其主要缺点。笔者针对其缺点作了五项改进,研制出新型的BJ-110钻孔弹模计。标定试验表明,古德曼千斤顶的接触面匹配不良及承压板弯曲导致测量值过小的问题已被新设备克服,压力和位移的分辨率提高了5倍,测定的岩体变形模量不再需要修正。对于岩石,当采用2β=45°的承压块时,测定值与真实值之偏差不大于10％;对于钢、铁等高弹模材料,当采用2β=30°承压块时,其偏差不大于5％。现场试验表明,测定值E_calc与岩石常规试验结果完全一致。     

Evaluating temperature effects on leaching behavior of geogenic arsenic and boron from crushed excavated rocks using shaking and nonshaking batch tests

The leaching behavior of arsenic and boron is evaluated in this work through two types of excavated rocks with geogenic contaminants under different temperatures. Excavated rocks with geogenic contaminants are expected to be used in embankments with appropriate countermeasures being taken against the risks brought about by geogenic contamination. The leaching behavior might change because of changes in the ground temperature. However, the effects of temperature on the leaching behavior of such rocks have not been well examined. Herein, batch leaching tests at temperatures between 5 and 60 °C were performed under shaking and nonshaking conditions. Mudstone and shale rock were crushed into particles smaller than 2 mm, which were required for the tests. The tests were carried out for durations ranging from 6 h to 15 days because changes in leaching kinetics also require careful evaluation. After conducting the nonshaking tests for 15 days at 40 °C, the mudstone sample leached arsenic and boron at concentrations of approximately 0.7 and 1.0 mg/L, respectively. The arsenic and boron concentrations were about 20 and 40% higher than those of the sample leached at a temperature of 20 °C. Elevated temperatures were seen to increase the leaching kinetics of the toxic elements. For the shale rock sample, the leaching rate for arsenic was 7.7 × 10^-2/h at 40 °C, which was about 2.5 times greater than the value at 30 °C. The nonshaking tests showed higher leaching amounts of arsenic and boron than the shaking tests, especially at elevated temperatures. As unrealistic estimations should be avoided, nonshaking tests are suggested. Moreover, nonshaking tests lasting longer than 6 h are necessary due to the relatively slow dissolution of minerals.     

Determination of the pressure of backfill soil against retaining walls on a centrifugal machine

Conclusions 1. Use of the method of centrifugal modeling in studying lateral soil pressure on retaining walls makes it possible to ascertain not only general laws governing the formation of lateral pressure, but also the character of its variation as a result of technological peculiarities of the soil's placement in the backfill. 2. The curve of lateral soil pressure that is formed in the initial period does not change thereafter with increasing height of backfill and increasing stresses, i.e., the quality of backfill placement determines the lateral pressure over the entire period of subsequent service. 3. The initial density of the backfill soil significantly affects the lateral soil pressure in the state of repose (for a stationary wall). The higher the initial density, the lower the coefficient ξ, and conversely. For noncohesive soils, the maximum pressure was observed for an uncompacted backfill (ξ=0.42−0.45). 4. An active soil pressure, which is approximately 25% lower than the pressure at rest, is formed in the backfill as the top of the wall departs from it by the amount (1/100)H – (1/200)H. 5. As the wall departs from the soil and subsequently returns, its lateral pressure in the initial position does not return to the initial value, and a reactive soil resistance begins to form at once. For wall deformations, consequently, the backfill must be treated as an elastic medium. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 5, pp. 18–20, September-October, 1990.     

Experimental investigations of bearing capacity of bored-cast-in-place tapered piles

Conclusions 1. The investigated types of bored-cast-in-place tapered piles with a taper angle of 1°20′, 2°, and 2°40′ have a specific bearing capacity which exceeds by 20–30% the specific bearing capacity of cylindrical piles having the same length. 2. The bearing capacity of tapered piles and the consumption of materials in them increase in direct proportion to the increase in the taper angle. The most rational type within the investigated limits is a bored-cast-in-place pile with a taper angle of 2.5°. 3. Introduction of tapered piles based on the above investigations has made it possible to obtain a significant economic effect. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 2, pp. 5–7, March–April, 1990.     

Weathering indices and their applicability for crystalline rocks

In the recent past, several weathering indices have been proposed to characterize the extent of weathering and weatherability depending upon the nature and requirement of the study. The weathering index provides a quantitative measure of the extent of weathering of rock; hence it can provide input to the prediction models to assess the strength and deformational properties of rocks and classifications of weathered rock material. In the present study some of the important weathering indices, broadly categorized as chemical, (micro) petrographical and engineering weathering indices, are reviewed and studied experimentally for three common rocks of India, namely granite of Malanjkhand, basalt of Nagpur and quartzite of Delhi, along with results of other rocks reported by other researchers. The study reveals that none of the existing chemical weathering indices is valid for genetically different common rock types and useful for engineering purposes. However, loss on ignition (LOI) may provide an approximate estimation of altered minerals (clays and hydroxides) in tested rocks. It has also shown good correlation with petrographic indices and engineering index properties. Among the petrographic indices, crack density (ρ_cr) and unsound constituent (an input to the micropetrographic index) indices provide good correlation with engineering index properties. To quantify the extent of weathering in terms of strength degradation due to weathering in rock, an index is suggested – strength ratio (R_s) – which is the percentage of uniaxial compressive strength (σ_c) of weathered rock with respect to σ_c of fresh rock. Its significance is shown statistically through the relationships with other indices for several rock types including sedimentary and metamorphic rocks. Electronic Publication     

Three-dimensional modeling of borehole data cored from engineering rock mass

Vast data from the drilling and geophysical prospecting are reliable original information to describe the space state of engineering rock mass, and one of the main difficulties in three-dimensional (3D) modeling of engineering rock mass is the processing of the primary data. From the view-point of 3D modeling, the engineering rock masses are classified as four basic types according to their geometric characteristics of geologic structure: (1) continuum rock mass; (2) discontinuous rock mass; (3) overturned fold rock mass and (4) intrusive rock mass. Because drilling data are very important to describe the characters of multi-scale of the spatial data for rock mass, the rule of how to process drilling data is developed to help appropriately display them in the viewpoint of 3D space. According to the characteristics of rock mass layers, the processing method of drilling data for 3D modeling of engineering rock masses, along with the layer thicknesses, is also proposed, including the evaluation rules and the extensive direction for original borehole data. By this method, the typical 3D data modeled is completed and the model form of the engineering rock mass is developed. By this example, it is finally verified that the method presented is successful and feasible to process 3D engineering rock mass. __________ Translated from Chinese Journal of Rock Mechanics and Engineering, 2005, 24(11): 1 821–1 826 [译自: 岩石力学与工程学报]