Large Rock Blocks Research Articles

Research on the mechanism and application of wedge cutting blasting with hole-inner delay

To increase the efficiency of deep-hole blasting driving in mine rock tunnels, an innovative pattern of wedge cutting blasting with hole-inner delay was proposed. First, the blasting mechanisms of conventional and innovative wedge cutting patterns were theoretically investigated. The results showed that the resistance from large upper rock blocks and the clamping action from the surrounding rock were the major challenges of conventional cutting methods. For the innovative cutting pattern, under the conversion of the spatial distribution and release sequence of blasting energy, the first blasting of the upper charge can strengthen the breaking of the upper rock mass and create a new free surface, which provides favorable conditions for the delayed blasting of the bottom charge. Second, finite element models of two cutting patterns were established and solved, and the simulation results visually revealed the propagation of a stress wave. Critically, the stress strength in the upper cavity increased by 66–83% under the action of the upper charge, which was conducive to the breaking of the upper rock mass and the generation of a new free surface. Therefore, the rock mass in the bottom cavity can be readily broken and discharged. Ultimately, field applications were executed in a rock tunnel. Compared with a conventional cutting pattern, the proposed innovative cutting pattern can prominently increase the cycle advance and hole utilization and greatly reduce the unit consumption of explosives and detonators. This research confirms the usability of the innovative wedge cutting pattern with hole-inner delay in deep-hole blasting driving of rock tunnels.

Coevolving edge rounding and shape of glacial erratics: the case of Shap granite, UK

Abstract. The size distributions and the shapes of detrital rock clasts can shed light on the environmental history of the clast assemblages and the processes responsible for clast comminution. For example, mechanical fracture due to the stresses imposed on a basal rock surface by a body of flowing glacial ice releases initial “parent” shapes of large blocks of rock from an outcrop, which then are modified by the mechanics of abrasion and fracture during subglacial transport. The latter processes produce subsequent generations of shapes, possibly distinct in form from the parent blocks. A complete understanding of both the processes responsible for block shape changes and the trends in shape adjustment with time and distance away from the source outcrop is lacking. Field data on edge rounding and shape changes of Shap granite blocks (dispersed by Devensian ice eastwards from the outcrop) are used herein to explore the systematic changes in block form with distance from the outcrop. The degree of edge rounding for individual blocks increases in a punctuated fashion with the distance from the outcrop as blocks fracture repeatedly to introduce new fresh unrounded edges. In contrast, block shape is conservative, with parent blocks fracturing to produce self-similar “child” shapes with distance. Measured block shapes evolve in accord with two well-known models for block fracture mechanics – (1) stochastic and (2) silver ratio models – towards one or the other of these two attractor states. Progressive reduction in block size, in accord with fracture mechanics, reflects the fact that most blocks were transported at the sole of the ice mass and were subject to the compressive and tensile forces of the ice acting on the stoss surfaces of blocks lying against a bedrock or till surface. The interpretations might apply to a range of homogeneous hard rock lithologies.

Bed Load Transport and Alternation of a Gravel-Bed River Morphology within a Vicinity of Block Ramp: Classical and Numerical Approach

In current river management, we very often use environment-friendly hydraulic structures when it is required for river bed or river bank protection due to erosion of a river channel. Block ramps are one of many methods used to stabilize river beds. They provide a semi-natural solution to certain river engineering problems in mountain streams. When building block ramps, one can use the dissipative behavior of large rock blocks or boulder elements randomly placed on the river bed to enhance fish migration in an upstream direction; thus, they can serve as fish passes. In this paper, we present the results of the numerical modelling of a bed load transport and the morphological changes of a river bed where a block ramp was designed and built. The main aim of the study was to investigate the difference of 2D modelling of a bed load transport along the mountain stream reach with boulder ramps in comparison to the classical methods of Hjulström, Shields, and Russian standard ST-24-2396. The work was carried out on the stream of one of the chosen low-head hydraulic structures, where 25 identical block ramps were constructed for river training reasons. The novel approach of our study is, for the first time in the field, to show a very detailed analysis of block ramp influence on sediment transport and river morphology changes compared to the classical understanding of those phenomena, as well as 2D model results to give hydraulic engineers an inside look into classical and modern approaches of bed load transport calculations. This might be helpful for designing such kinds of hydraulic structures in the future, in all regions where sediment transport calculations are important but do not always require sophisticated modelling.

Development and applicability verification of laboratory cyclic box shear test method using large rock blocks

Development and applicability verification of laboratory cyclic box shear test method using large rock blocks

A New Approach to Represent Impact of Discontinuity Spacing and Rock Mass Description on the Median Fragment Size of Blasted Rocks Using Image Analysis of Rock Mass

Several in-situ rock mass properties and blasthole parameters can affect the rock fragmentation. Because of the complexity of the variables affecting the fragmentation results of blasted rocks, to predict a proper value of the median fragment size has long been a difficult task. The blastability index (BI) represents the effect of five parameters of rock mass description (RMD), joint plane spacing (JPS), joint plane orientation, specific gravity and uniaxial compressive strength on the rock fragmentation. The median discontinuity spacing significantly varies with varying the scanline direction and an acceptable value of the median discontinuity spacing will not be expected in practice. The JPS rating also has a constant value of 20 for a wide range of joint spacing values between 0.1 and 1 m, whereas joint spacing can be in this range for most cases. A new method using image analysis of the in-situ rock mass was applied to represent JPS and RMD (belonging to one of the cases: friable, blocky and massive) as an alternative solution. The images contain the details of all individual discontinuities and interlocked in-situ small and large rock blocks. BI, rock strength factor, blasthole parameters, powder factor, fragment size distribution of blasted rock and in-situ block size distribution using image analysis technique were assessed in 15 zones of Sungun open pit copper mine, Angouran lead and zinc open pit mine, Bonab silica mine, Soufian limestone mine and Rashakan limestone mine. The results for rock mass properties and blasthole patterns cover a wide range using different mines. The fragment size distribution was assessed by Split Desktop program with proper delineating images using the Pixler software and blasting was carried out with electric delay detonators. The relations between fragment size and parameters such as in-situ block size (F50), σc, rating of joint plane orientation, powder factor (q), ϕh, Q and Lc were analyzed. The relations with high correlations were achieved by applying the new approach for the defined conditions. Not only the problem of assessing discontinuity spacing has been improved using this method but also the lower number of parameters that properly represent the factors affecting the rock fragmentation have been used. The results were also analyzed by the Sanchidrian and Ouchterlony model and modified Kuz–Ram models. The fragment size obtained by the new method in this study, Sanchidrian and Ouchterlony model and extended modified Kuz–Ram model by Cunningham (in: Proceedings of 3rd world conference on explosives and blasting, Brighton, 2005) after using correction factor [c(A)] significantly better fitted to the results than the modified Kuz–Ram models by Cunningham (in: Fourney, Dick (eds) Proceedings of 2nd international symposium on rock fragmentation by blasting, Keystone, 1987) and Gheibie et al. (Int J Rock Mech Min 46(6):967–973, 2009).

Moderate blasting technologies: Experience and prospects for introduction in Polyus mines

It is commonly known that rock fragmentation by blasting is the most economically efficient method to prepare large volumes of rock mass to excavation and handling. The drilling and blasting technology accepted by a mine governs both rock fragmentation quality and mining safety connected with slope stability. Therefore, optimization of drilling and blasting is an objective calling for the effective blast design and control. This article presents the main principles and methods of moderate blasting implemented at Polyus company towards minimization of impact on pit walls and benches. The main point is stagewise reduction of the dynamic effect exerted by blasting on rock mass when approaching the ultimate pit limits. Polyus company initiated the far and wide review and introduction of the best international practices for improvement of blasting operations near the ultimate pit limits. The article describes the activities undertaken within implementation of projects on drilling and blasting technology justification and improvement to enhance stability of pit walls and, as a consequence, to reduce geotechnical hazards. As a complimentary measure to abate seismic effect of explosions on adjacent rock mass, the nonelectric blasting is replaced by electronic blast initiation systems with more accurate delay intervals, which almost nullifies probability of simultaneous ignition of two or more charges and ensures, thereby, the acceptable and seismically safe modes of blasting of large rock blocks. Furthermore, the introduction of the electronic blasting cardinally changes the approach to blasting order and sequence per intervals in blast holes depending on the current task within a block to be blasted.

Full-Scale Linear Cutting Tests to Propose Some Empirical Formulas for TBM Disc Cutter Performance Prediction

Determination of the TBM disc cutter performance at the optimum rock cutting condition is very important, but the existing theoretical, laboratory, numerical or empirical methods still have some shortcomings. Full-scale rock cutting test is regarded as the most accurate and reliable method in the laboratory, but it still requires large rock blocks and specific testing equipment, which make the use of this method very limited and costly. Thus, by collecting, analyzing and formulizing the results of many full-scale linear cutting tests, this study partly overcomes the shortcoming of the full-scale rock cutting test and proposes some new empirical formulas to predict TBM disc cutter performance in a much easier and less costly way. First, this study reveals the general rules to characterize the change of rock cutting results with the increase of rock uniaxial compressive strength and cutter penetration depth by conducting full-scale linear cutting tests on five different rock types. Then, by analyzing a large amount of full-scale linear cutting test results, this study correlates the TBM disc cutter performance at the optimum rock cutting condition with rock uniaxial compressive strength and a widely used semi-theoretical prediction model. The new proposed empirical formulas in this study only use rock properties, cutter geometries and cutting geometries to design the machine specifications and select the TBM operation parameters, which is a much easier and less costly method.

Influence of water content and shear rate on the mechanical behavior of soil-rock mixtures

Soil-rock mixtures (S-RMs) are widely distributed in the nature. The mesoscopic deformation and failure mechanisms as well as the macro-mechanical behaviors of the S-RMs depend largely upon the rate of deformation, water content and particle sizes. In this research, a series of large-scale direct shear tests with different water contents and different grain-size distributions were conducted to study the influence of the aforementioned factors on the mechanical properties of the S-RMs. Due to the effect of the rock blocks’ breakage in the S-RMs, the relationship between the shear strength and the vertical stress of S-RM follows a power law instead of a linear one. It is found that there exists a threshold value for the vertical stress during the shearing process, below which the soil strength is mainly determined by the inter-locking of particles and the re-arrangement of meso-structure, and otherwise large-sized rock blocks are gradually broken into smaller fragments, resulting in a decrease in the soil strength. The shear rate can also significantly influence the degree of particle breakage and the meso-structural rearrangement of the S-RMs, namely, under low shear rate, the particles of the samples are fully broken resulting in enhanced macro-strength. As a result, the lower the shear rate, the higher the macroscopic strength. So under unsaturated conditions, the water content will affect the strength of the S-RMs by reducing the strength of rock blocks. As the water content increases, the soil strength decreases gradually, and assumes a moderate value when the water content reaches 8%. At the same water content, the soil strength increases with the sizes of large rock blocks. For the occlusion, breakage and structure re-arrangement of the oversized rock blocks inside S-RM, which have a huge influence on the mechanical characteristics of the samples.

Rock fragmentation under different installation polar angles of TBM disc cutters

The disc cutters of tunnel boring machine (TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established to study the rock fragmentation law between adjacent disc cutters with different polar angles based on particle flow code (PFC). The influence of polar angle of adjacent disc cutters on rock cracks and stresses under different cutter spacing and penetration was studied. Research shows that polar angle difference leads to the discontinuity of rock-fragmentation process by adjacent cutters. The effect of rock-fragmentation is influenced by the cutting depth difference between adjacent cutters. The effect of rock-fragmentation performed best, meanwhile large rock blocks were flaked when the difference of cutting depth is half of the penetration. Too large or small difference of the cutting depth will cause high specific energy consumption of rock fragmentation. The specific energy consumption is relatively small when the difference of cutting depth is half of the penetration.

GEOTECHNICAL INVESTIGATION OF THE ROCK SLOPE STABILITY PROBLEMS OCCURRED AT THE FOUNDATIONS OF THE COASTAL BYZANTINE WALL OF KAVALA CITY, GREECE

The coastal Byzantine wall of Kavala is located at the Panagia peninsula and it is founded on the Simvolou granite. The granite rock mass appears to be fractured by joint sets with very high persistence (>20m) and very wide spacing (60cm – 2m), forming large rock blocks. Further more, the Panagia peninsula is intersected by numerous parallel normal faults, forming extended zones of intensively fractured rock mass. Along the coastline the granite appear to be eroded by the sea waves, forming small gulfs around the faults. The Byzantine wall is founded along the edge of the fractured slopes forming the coast line of the peninsula, arising issues about the safety of the historical construction. The joint sets form numerous rock wedges with unfavourable orientation, many sections of the slopes are undercut by the wave erosion and in the majority of the fault zones the rock mass presents intensive fragmentation. The above described condition of the rock mass was recorded in detail along the entire coast line and all unstable sections were located. A full set of support measures was proposed for all unfavourable sections aiming to the improvement of the geotechnical behaviour of the rock mass, constituting the foundation formation of the Byzantine wall.

Geophysical Monitoring of Underground Constructions and its Theoretical Basis

To avoid damage of rock mass, their collapse into underground space, danger for equipment and risks for human life, during construction and exploitation of large engineering projects (e.g. underground spaces, tunnels, machine halls, etc.) in-situ geotechnical and geophysical monitoring is carried out. Geophysical monitoring is based on observations of the elastic shear – and longitudinal wave velocities ( Vs and Vp , respectively) and Acoustic Emission (AE). The behaviors of the elastic velocities and parameters of AE during rock deformation depend on the types of the future failure that, in turn, are defined by the structure and properties of the medium and characteristics of stress state s 3 /s 1 and hydrostatic pressure. These velocity variations are defined by difference in effective parameters of forming microfractures, whose geometry is distinguished at different modes of stress state. At that character of interaction between microfractures determines the types of the macrofailure. In this study, we discuss the behaviors of longitudinal wave velocities and acoustic emission during loading of large rock blocks and underground opening orienting measurements along maximum ( s 1 ) and minimum ( s 3 ) stresses. It is shown that velocity variations along the maximum stress is more informative at elastic phase of rock deformations (velocity increases), whereas velocity variations along axis of the minimum stress is more informative at the stage of nonlinear rock deformation (velocity begins to decrease during microfractures occurrence). These regularities are well observed at unloading rock mass in the Zhinvali tailrace tunnel where geophysical monitoring assisted in the construction. This knowledge could be used in planning and monitoring the stability of underground structures.

Rockfall Modelling with Remedial Design and Measures along Part of a Mountainous Settlement Area, Southern Turkey

In June 2011, a heavy rainfall triggered a number of rockfalls from steep slopes and on slopes made of soft to loose soils capped by inhomogeneous hard rock blocks and masses in the Düziçi Town of Osmaniye Province in Turkey. Large rock blocks had damaged 15 prefabricated hotel rooms whereas the slope movement blocked the major road between Duzigi and hot spring facilities at numerous locations along 280 m. This paper describes remedial measures and design recommended according to the modelling process based on the collection of data and simulation of rockfall with Rocscience RockFall 5.0 software.

Ground pressure and overlying strata structure for a repeated mining face of residual coal after room and pillar mining

To investigate the abnormal ground pressures and roof control problem in fully mechanized repeated mining of residual coal after room and pillar mining, the roof fracture structural model and mechanical model were developed using numerical simulation and theoretical analysis. The roof fracture characteristics of a repeated mining face were revealed and the ground pressure law and roof supporting conditions of the repeated mining face were obtained. The results indicate that when the repeated mining face passes the residual pillars, the sudden instability causes fracturing in the main roof above the old goaf and forms an extra-large rock block above the mining face. A relatively stable “Voussoir beam” structure is formed after the advance fracturing of the main roof. When the repeated mining face passes the old goaf, as the large rock block revolves and touches gangue, the rock block will break secondarily under overburden rock loads. An example calculation was performed involving an integrated mine in Shanxi province, results showed that minimum working resistance values of support determined to be reasonable were respectively 11,412kN and 10,743kN when repeated mining face passed through residual pillar and goaf. On-site ground pressure monitoring results indicated that the mechanical model and support resistance calculation were reasonable.

Hydrogeological monitoring and modelling in the S. Lorenzo road tunnel area (Passo della Morte, Udine) for the design of countermeasure works

In the eastern Italian Alps, a large deep-seated rock block slide affects the S. Lorenzo road tunnel (46°23'49 N, 12°42'51 E) along the National Road 52 Carnica, near to Passo della Morte (Udine Province); the tunnel was excavated through a fractured carbonatic rock mass overthrusted on clay-rich units. Previous studies of the unstable slope outlined the relationship between slope displacements and groundwater flow in the fractured rock mass. The conceptual geological model of the area, together with field observations, allowed specific investigation and monitoring activities to be defined in order to investigate this relationship. In particular, during the last years, six weirs were built and pressure transducers were installed in order to assess the total water discharge from the area. Moreover, 14 piezometers were drilled outside and inside the tunnel to monitor the hydraulic head. After 15 years of monitoring the groundwater system can be described in detail. In particular, results show a double flow system. The first is almost constant for all the year, while the second is influenced by rainfall events and is hosted in faults, fractures and joints in the western part of the tunnel, in the area of the larger and deep-seated rock slide. A three-dimensional groundwater flow model was built and calibrated along the total outflow from the road tunnel in order to better understand the interactions between groundwater flow and road infrastructure. In particular, the effects of countermeasures works, like the extension of the drainage adit in the carbonatic rock mass, was tested.

Triaxial tests of soil–rock mixtures with different rock block distributions

Triaxial tests on three types of soil–rock mixture (S-RM) samples with the same rock block content, but different grain size distributions, were performed in this study. To better understand the meso-mechanical behavior of soil–rock mixtures, one set of samples containing “oversized rock blocks” was designed. The oversized rock blocks in the other two sets were handled using the equivalent weight replacement method and the similar translation method. On this basis, the effect of the grain size distribution on the mechanical properties of the soil–rock mixtures was explored. The interlocking and the breakage of the large rock blocks were found to be two of the controlling factors of the mechanical properties of soil–rock mixtures. The deviator stress and the volumetric strain correlated well with the uniformity coefficient of the particle size distribution curve and performed differently under different confining pressure levels. Based on X-ray computed tomography (CT) slices of samples taken during the triaxial tests, the interaction of the internal rock blocks and the evolution of the sample meso-structure in the loading process were observed and analyzed; the present analysis provides explanations for the macroscopic mechanical behavior of soil–rock mixtures.

Full-Waveform Terrestrial Laser Scanning for Extracting a High-Resolution 3D Topographic Model: a Case Study on an Area of Archaeological Significance

This paper describes a method, which uses full-waveform terrestrial laser scanning to survey the surface of the slope below the Temple of Juno, located in the Valley of the Temples in Agrigento (Sicily, Southern Italy). The surface is characterized by the presence of large rock blocks, which have fallen down from the upper side; possible further detachments of rock blocks would cause a situation of general instability, with a very high risk to the archaeological structures in the near future. The methodology was designed to evaluate the potential of full-waveform laser scanning technology for the production of a very high resolution 3D topographic model of the slope, to be used as a support for the interpretation of geomorphological processes and for geotechnical analysis.

Geology, geomorphology and dynamics of the 15 February 2010 Maierato landslide (Calabria, Italy)

On 15 February 2010, as a result of intense and long-lasting rainfalls, a large landslide affected a wide area near the town of Maierato (Calabria, Italy). The studies conducted – including (i) aerial photo interpretation, (ii) geological and geomorphological field investigations, (iii) interpretations of lithology and stratigraphy from borehole data, and (iv) observation of videos filmed during the main diastrophic phases of the landslide and of antecedent Google Street View® images – allowed researchers to reconstruct the geological and tectonic setting of the slope and the internal structure of the landslide with the estimation of the depth of the sliding surface, the triggering mechanisms and its evolution.The analysis of the prelandslide event setting demonstrates that this mass movement is the reactivation of a preexisting landslide of alleged seismic origin, remaining at an incipient stage.The Maierato landslide occurred on a gentle slope made of late Miocene to Plio-Pleistocene clastic and evaporitic sedimentary rocks. The main basal failure surface that developed on the hemipelagic marls has a maximum depth of 50m. The volume of the landslide is ~5million cubic meters.The type of landslide movement is a complex one, consisting of a very rapid slide of rock and earth and of flow of debris and earth. The landslide clearly shows three major types of failure mechanisms: the first type is described as a rapidly moving rotational slide where back-tilted blocks of sediment are preserved; the second type includes a very rapidly moving translational slide of large rock blocks; the third type includes sudden, extremely rapid flow-slides where the slide material is disaggregated while flowing downward along a gentle slope.The slide is a compound one, with a retrogressive evolution and transformation into earth and debris flow during the failure. After the triggering of the landslide, and as a result of the relevant displacement, an important portion of the lower evaporitic unit (Calcare di Base Formation), close to the failure surface, collapsed, thereby undergoing a quick change of its mechanical behavior that became similar to that of a viscous fluid. During the landslide evolution, large rocky blocks consisting of Miocene evaporitic limestones, Pliocene silty clays, and sands were rafted, without severe disturbance, on the destructurated and fluidized limestone. The intense destructuration and the presence of water transformed the limestone (in the lower parts of the unit) into a viscous material that was squeezed out of the landslide mass through the jags between the several rafted rocky blocks and along the natural levees of flow tongue.This event is a rather frequent combination of mass movements made complicated and spectacular by the fluidization of the weak limestone that imparted great dynamics to the movements. Such fluidization is an infrequent phenomenon especially in this geological context.

Foraminiferal colonization related to the Zechstein (Lopingian) transgression in the western part of the Wolsztyn Palaeo-Ridge area, Western Poland

The basal Zechstein succession in SW Poland is dominated by breccias and/or conglomerates or extraclast-bearing bioclastic limestones, which were deposited during rapid flooding of the pre-existing intracontinental basin in the early Lopingian (Late Permian). Of these, the boulder-cobble breccias and conglomerates are interpreted as deposited in a rocky shore-zone where density flows and upwelling prevailed. The breccias gradually pass up into bryozoan (or other bioclastics) grainstones. The matrix-supported breccias were deposited as large extraclasts and blocks of Carboniferous rock were rolled down or detached from a cliff and were then either embedded into a carbonate sand or formed a framework supplying voids that could be colonized by tubular encrusting foraminifers. These foraminifers abound in all basal Zechstein facies (except in the debris-flow deposits) and are attributed to Palaeonubecularia . The associated faunas include other foraminifers (uniserial and hemigordiopsids), bryozoans, brachiopods, bivalves, gastropods, and microbial deposits. The prolific growth of tubular encrusting foraminifers has resulted from nutrient supply from the basin by upwelling. Botryoidal aragonite cements (also interpreted as due to upwelling) also characterize the basal Zechstein strata, although they were previously reported only from the upper Zechstein Limestone. The d13C values of the basal Zechstein deposits show small variation and oscillated around 4.0‰, suggesting that these deposits are younger than the Kupferschiefer. The basal Zechstein strata in SW Poland consisting of breccias and/or conglomerates or bioclastic limestones (often containing extraclasts of Carboniferous rocks) originated following the rapid flood of the pre-existing intracontinental basin; this general transgression was followed by subsequent increases of sea level. Boulder-cobble breccias and conglomerates occurring at the base of the Zechstein are interpreted as a rocky-shore deposit; d epositional processes of the basal Zechstein deposits were dominated by density flows. The breccias are gradually passing into bioclastic (mostly bryozoan) grainstones, and m atrix-supported breccias originated when usually large extraclasts and blocks of Carboniferous rocks were rolled down or detached from cliff and were either embedded into the carbonate sandy material or formed a framework supplying voids that could be colonized by tubular encrusting foraminifers. These foraminifers abound in all basal Zechstein facies and are included into Palaeonubecularia . They are accompanied by other foraminifers (uniserial, Agathammina , spiral) as well as bryozoans, brachiopods, bivalves, gastropods and microbial formations. The prolific growth of tubular encrusting foraminifers has resulted from supply of the nutrients from the basin by the upwelling. The botryoidal aragonite cements (interpreted as due to upwelling as well) occur in the basal Zechstein strata; previously they were reported only from the upper part of the Zechstein Limestone. The δ 13 C values of basal Zechstein deposits show small variation and oscillated around 4.0‰; they strongly suggest that these deposits are younger than the Kupferschiefer.

Chapter 9 Materials for construction in deserts

Civil engineering constructions of all kinds use large quantities of natural materials ranging from soils and clays through sand, gravel and crushed rock to large blocks of rock, which may be used as armourstone, for shaping into dimension stone, or as cladding, tiles or pavers. Excavation, cuttings and ground preparation associated with many construction projects require large volumes of soil and rock to be removed. Where possible, this bulk material is reused as foundation layers for buildings and roads, and, more commonly, as fill for embankments or bunds. Today, there is increasing pressure to reuse or recycle the demolition waste materials from redundant buildings. Timber is a scarce commodity in desert regions and is usually imported. Consequently, it is often reused or used as a fuel source. However, it is also becoming more common for solid building wastes such as concrete and brick to be recycled as ‘secondary’ aggregate or fills. Natural geological materials of all kinds may be found in desert regions and are described in Chapters 3 and 5. They are similar to materials found in other parts of the world, but the special environmental conditions of deserts (as described in Chapters 2–4) can lead to the alteration of these geological materials to form unique associations of rock, and also to create new ones that are specific to deserts. Where possible, the bulk natural raw materials for construction in deserts are sourced locally, which may imply that less than ideal material will have to be used in some circumstances. The uses of natural materials in construction can be categorized under the following general applications:

Electrochemical behavior of H3PW12O40/ acid-activated bentonite powders

Electrochemical behavior of 12-tungstophosphoric acid (HPW)/acid-activated bentonite (AAB) powders with various loadings of HPW was investigated. The physicochemical properties of the prepared powders were examined by X-ray powder diffraction, nitrogen adsorption-desorption isotherms, atomic force microscopy and cyclic voltammetry measurements. The results indicated that the prepared powders are composed mainly of oriented domains of large rock blocks, probably resulting from a preferable deposition of bentonite particles having a face-to-face interaction. The particles had a mainly disordered mesoporous structure with a pore volume that varied according to the pore size in the range of 2-50 nm. In addition, the particles had crystallite size between 4.9 and 9.0 nm. The electrocatalytic activities of prepared HPW/Aelectrodes were studied in the oxidation of NO2-ions and the results revealed that the electrodes possessed relatively higher nitrite oxidation currents than Aelectrode. The best electroactivity was observed for HPW3/Aelectrode (AAB+20 wt. % HPW) and the limit of detection (3?) was determined as 8 ?M.