Fracture Traces Research Articles

High-Resolution Digital Elevation Modeling from TLS and UAV Campaign Reveals Structural Complexity at the 2014/2015 Holuhraun Eruption Site, Iceland

Fissure eruptions are commonly linked to magma dikes at depth, associated with elastic and anelastic surface deformation. Elastic deformation is well described by subsidence above, uplift and lateral widening perpendicular to the dike plane. The anelastic part is associated with the formation of a graben, bordered by graben parallel faults that might express as sets of fractures at the surface. Additionally secondary structures, like push ups, bends and step overs yield information about the deforming domain. The formation of such structures associated with fissure eruptions, however, is barely preserved in nature because of the rapid erosion or sediment coverage. Therefore, simple normal fault displacements are commonly assumed at dikes. At the 2014/2015 Holuhraun eruption sites (Iceland), evidence is increasing that the developing fractures are showing variations in their displacement modes. In an attempt to investigate these variations, a fieldwork mapping project combining Terrestrial Laser Scanning (TLS) and Unmanned Aerial Vehicle (UAV) based aerophoto analysis was realized. From this data, we generated locally high resolution Digital Elevation Models (DEMs) and a structural map that allows for identification of kinematic indicators and assessing particularities of the observed structures. We identified 315 fracture segments from satellite data. For single segments we measured strike directions including the amount of opening and opening angles, indicating that many of the measured fractures show transtensional dislocations. Out of these, 81 % are showing significant left-lateral slip, only 17% right-lateral slip and 2% pure tensile opening. We show that local complexities in the fracture traces and geometries are closely related to variations in the transtensional opening direction. Moreover, we identified local changes in fracture azimuths and offsets close to eruption sites, which we speculate to be associated with geometrical changes in the magma feeder itself. Results highlight that opening of fractures associated with an erupting fissure commonly show transtensional modes having both, left-lateral and right-lateral slip, with important implications for interpreting the expression of surface structures at rift zones elsewhere. Results further highlight the great value of UAV based high resolution data to contribute to the integrity of observations of structural complexities at local geologic events.

Microstructure, SDAS and Mechanical Properties of A356 alloy Castings Made in Sand and Granulated Blast Furnace Slag Moulds

Abstract Investigations were carried out to ensure the granulated blast furnace (GBF) slag as an alternative mould material in foundry industry by assessing the cast products structure property correlations. Sodium silicate-CO2 process was adopted for preparing the moulds. Three types of moulds were made with slag, silica sand individually and combination of these two with 10% sodium silicate and 20 seconds CO2 gassing time. A356 alloy castings were performed on these newly developed slag moulds. The cast products were investigated for its metallography and mechanical properties. Results reveal that cast products with good surface finish and without any defects were produced. Faster heat transfers in slag moulds enabled the cast products with fine and refined grain structured; and also, lower Secondary Dendrite Arm Spacing (SDAS) values were observed than sand mould. Slag mould casting shows improved mechanical properties like hardness, compression, tensile and impact strength compared to sand mould castings. Two types of tensile fracture modes, namely cleavage pattern with flat surfaces representing Al−Si eutectic zone and the areas of broken Fe-rich intermetallic compounds which appear as flower-like morphology was observed in sand mould castings. In contrast, GBF slag mould castings exhibit majority in dimple fracture morphology with traces of cleavage fracture. Charpy impact fractured surfaces of sand mould castings shows both transgranular and intergranular fracture modes. Only intergranular fracture mode was noticed in both GBF slag and mixed mould castings.

A numerical manifold method model for analyzing fully coupled hydro-mechanical processes in porous rock masses with discrete fractures

In this study, a numerical manifold method (NMM) model was developed for fully coupled analysis of hydro-mechanical (HM) processes in porous rock masses with discrete fractures. Using an NMM two-cover-mesh system of mathematical and physical covers, fractures are conveniently discretized by dividing the mathematical cover along fracture traces to physical cover, resulting in a discontinuous model on a non-conforming mesh. In this model, discrete fracture deformation (e.g. open and slip) and fracture fluid flow within a permeable and deformable porous rock matrix are rigorously considered. For porous rock, direct pore-volume coupling was modeled based on an energy-work scheme. For mechanical analysis of fractures, a fracture constitutive model for mechanically open states was introduced. For fluid flow in fractures, both along-fracture and normal-to-fracture fluid flow are modeled without introducing additional degrees of freedom. When the mechanical aperture of a fracture is changing, its hydraulic aperture and hydraulic conductivity is updated. At the same time, under the effect of coupled deformation and fluid flow, the contact state may dynamically change, and the corresponding contact constraint is updated each time step. Therefore, indirect coupling is realized under stringent considerations of coupled HM effects and fracture constitutive behavior transfer dynamically. To verify the new model, examples involving deformable porous media containing a single and two sets of fractures were designed, showing good accuracy. Last, the model was applied to analyze coupled HM behavior of fractured porous rock domains with complex fracture networks under effects of loading and injection.

PERCOLATION LAWS OF A FRACTAL FRACTURE-PORE DOUBLE MEDIUM

The fracture-pore double porosity medium is one of the most common media in nature, for example, rock mass in strata. Fracture has a more significant effect on fluid flow than a pore in a fracture-pore double porosity medium. Hence, the fracture effect on percolation should be considered when studying the percolation phenomenon in porous media. In this paper, based on the fractal distribution law, three-dimensional (3D) fracture surfaces, and two-dimensional (2D) fracture traces in rock mass, the locations of fracture surfaces or traces are determined using a random function of uniform distribution. Pores are superimposed to build a fractal fracture-pore double medium. Numerical experiments were performed to show percolation phenomena in the fracture-pore double medium. The percolation threshold can be determined from three independent variables (porosity [Formula: see text], fracture fractal dimension [Formula: see text], and initial value of fracture number [Formula: see text]). Once any two are determined, the percolation probability exists at a critical point with the remaining parameter changing. When the initial value of the fracture number is greater than zero, the percolation threshold in the fracture-pore medium is much smaller than that in a pore medium. When the fracture number equals zero, the fracture-pore medium degenerates to a pore medium, and both percolation thresholds are the same.

A comparison of lineament and fracture trace extraction from LANDSAT ETM+ panchromatic band and panchromatic aerial photograph in Gunungsewu karst area, Java-Indonesia

This paper aims at exploring interpretability of the panchromatic band of Landsat Enhanced Thematic Mapper Plus (ETM+) compared to the panchromatic aerial photograph in lineament and fracture trace extraction. Special interest is addressed to karst terrain where lineaments and fracture traces are expressed by aligned valleys and closed depressions. The study area is an single aerial photographic coverage in the Gunungsewu Karst, Java-Indonesia which is characterized by a lineament-controlled cone karst and labyrinth-cone karst. The result shows that the recording time of the Landsat ETM+ with respect to the shadow resulting from the sun illumination angle is the key factor in the performance of lineament and fracture traces extraction. Directional filtering and slicing techniques significantly enhance the lineament interpretability of the panchromatic band of Landsat ETM+. The two methods result in more lineaments and fracture traces which T-test affirm in 0.001 and 0.004 significant levels. Length based lineament analysis attains a better result compared to frequency based analysis.

Reconstruction of the water content at an interface between compacted bentonite blocks and fractured crystalline bedrock

High-density sodium bentonite combines a low permeability with a swelling behavior, which constitute two important qualities for engineered barriers in geological disposal of spent nuclear fuel. For example, the KBS-3V method developed in Sweden and Finland is planned to include compacted bentonite as the buffer material to embed canisters containing the spent nuclear fuel packages in deposition holes in deep crystalline bedrock. The partially saturated bentonite buffer will then swell as it takes up groundwater from the surrounding rock. It is important to quantify the water content evolution of the installed buffer to correctly predict the development of the swelling pressure and the prevailing conditions (thermal, mechanical, chemical and biological). This study aimed at quantifying the water content profile at the surface of a cylindrical bentonite parcel retrieved after in situ wetting in fractured crystalline bedrock. We demonstrate the possibility of using regression-kriging to quantitatively include spatial information from high-resolution photographs of the retrieved bentonite parcel, where more water saturated areas appear as relatively dark shades, along with bentonite samples, where detailed measurements of water content were performed. The resulting reconstruction is both exact regarding local sample measurements and successful to reproduce features such as intersecting rock fracture traces, visible in the photographs. This level of detail is a key step to gain a deeper understanding of the hydraulic behavior of compacted bentonite barriers in sparsely fractured rock. An improved scanning procedure could further increase the accuracy by reducing errors introduced by the geometrical transformations needed to unfold and stitch the different photographs into a single gray scale map of the bentonite surface. The application of this technique could provide more insights to ongoing and planned experiments with unsaturated bentonite buffers.

Extraction of three-dimensional fracture trace maps from calibrated image sequences

The routine application of digital survey technologies such as terrestrial lidar and photogrammetry to the characterization of fault and fractures in outcrop over the past decade has resulted in major advances in terms of the efficiency of discontinuity data acquisition. However, the reliance upon mesh- and point-cloud–based analysis approaches means that data sets obtained from these sources commonly offer heavily abstracted views of the measured fracture network due to the limited resolution of the input model. Here, we pre­sent an alternative approach that combines conventional two-dimensional (2D) image analysis with ray-tracing techniques to extract three-dimensional (3D) fracture trace maps from photogrammetrically calibrated image sequences. These 3D trace objects may be interrogated to obtain fracture network properties (trace length, intensity, and connectivity), with probabilistic methods used to estimate fracture orientation for high collinearity traces. Our approach possesses a number of advantages over existing digital surface reconstruction-based methods, with the use of a 2D pixel-based approach allowing established image-processing routines (e.g., edge detection/connected components analysis) to be applied to the characterization of fracture and fault properties. Moreover, the innately high resolution of the input images results in practically lossless 3D fracture trace representation, limiting truncation effects. As a result, the method is capable of resolving local varia­bility in higher-order fracture properties such as fracture intensity, which are difficult to derive using existing approaches. We demonstrate the approach on pervasively faulted Permian age exposures of the Vale of Eden Basin, UK.

Rock fracture skeleton tracing by image processing and quantitative analysis by geometry features

In rock engineering, fracture measurement is important for many applications. This paper proposes a novel method for rock fracture skeleton tracing and analyzing. As for skeleton localizing, the curvilinear fractures are multiscale enhanced based on a Hessian matrix, after image binarization, and clutters are post-processed by image analysis; subsequently, the fracture skeleton is extracted via ridge detection combined with a distance transform and thinning algorithm, after which gap sewing and burrs removal repair the skeleton. In regard to skeleton analyzing, the roughness and distribution of a fracture network are respectively described by the fractal dimensions D s and D b; the intersection and fragmentation of a fracture network are respectively characterized by the average number of ends and junctions per fracture N average and the average length per fracture L average. Three rock fracture surfaces are analyzed for experiments and the results verify that both the fracture tracing accuracy and the analysis feasibility are satisfactory using the new method.

FTIR, XRF, XRD and SEM characteristics of Permian shales, India

The emergence of shale gas as potential hydrocarbon resource has changed the global energy landscape. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), X-ray florescence (XRF) and Scanning Electron Microscope (SEM) characteristics of thirty nine borehole shale samples belonging to the Barakar (Lower Permian), Barren Measures (Upper Permian) and Raniganj (Upper Permian) Formations from different parts of Raniganj basin, India were studied. FTIR analysis indicates the presence of aromatic hydrogen, aromatic carbon, aliphatic C–H stretching, aliphatic C–H bending, OH functional group within the organic matter and presence of kaolinite, quartz and carbonates within the studied samples. XRF studies indicate that the shales have undergone intermediate to strong weathering condition, and are marked by presence of clay minerals mainly illite and kaolinite. In addition to illite, kaolinite and quartz, alkali feldspar, siderite and calcite were identified within the shales through XRD. Marked development of amorphous character was noted in the XRD plot of one heat affected shale sample. FTIR analysis of this sample also indicates removal of aliphatics and disordering of kaolinite within the sample due to the impact of heat. Through SEM studies different types of surface morphologies, different types of pores and pore shapes in organic matter were identified. SEM studies also indicate intimate mixing of organic matter and mineral matter in shales even at submicroscopic levels. This intimate association appears to have impact on the retention of hydrocarbons by the mineral matrix during Rock Eval pyrolysis. The various micropores, microcracks, fracture traces, macropores and vacuoles may play significant role in diffusion and flow of hydrocarbons.

Interfacial fracture strength and toughness of copper/epoxy-resin interfaces

We present results examining the interfacial fracture toughness of Cu2O/epoxy-resin interfaces, which is an important parameter in microelectronic packaging design. Tensiometer measurements of the epoxy-resin surface energy together with contact angle measurements of epoxy-resin/Cu2O wetting yield an estimate of the thermodynamic work of adhesion of 0.074 Jm−2. Double cleavage drilled compression (DCDC) and pull test samples were used to evaluate the critical stress intensity and strain energy release rate for interface fracture and found to be 0.05 MPa-m1/2 and 1.4 Jm−2. These sample geometries yielded only interface failure with no trace of fracture occurring in either the copper or the epoxy-resin component. The difference between the values of the thermodynamic work of adhesion and the critical strain energy release rate is attributed to plastic processes most likely occurring in the copper layer of the sandwich sample configuration of the DCDC sample.

Former dynamic behaviour of a cold-based valley glacier on Svalbard revealed by basal ice and structural glaciology investigations

AbstractLarge numbers of small valley glaciers on Svalbard were thicker and more extensive during the Little Ice Age (LIA), demonstrated by prominent ice-cored moraines up to several kilometres beyond present-day margins. The majority of these glaciers have since experienced a long period of strongly negative mass balance during the 20th century and are now largely frozen to their beds, indicating they are likely to have undergone a thermal transition from a polythermal to a cold-based regime. We present evidence for such a switch by reconstructing the former flow dynamics and thermal regime of Tellbreen, a small cold-based valley glacier in central Spitsbergen, based on its basal sequence and glaciological structures. Within the basal sequence, the underlying matrix-supported diamict is interpreted as saturated subglacial traction till which has frozen at the bed, indicating that the thermal switch has resulted in a cessation of subglacial sediment deformation due to freezing of the former deforming layer. This is overlain by debris-poor dispersed facies ice, interpreted to have formed through strain-induced metamorphism of englacial ice. The sequential development of structures includes arcuate fracture traces, interpreted as shear planes formed in a compressive/transpressive stress regime; and fracture traces, interpreted as healed extensional crevasses. The formation of these sediment/ice facies and structures is indicative of dynamic, warm-based flow, most likely during the LIA when the glacier was significantly thicker.

Structural Analysis and Tectonic Investigation of Chamshir Dam Site, South West Zagros

Geological factors play a major role in constructing and stability a dam. The study area is Chamshir Dam, which is located on the Zohreh River, 20 km southeast of Gachsaran City (southwest Iran). The satellite images are valuable means available to geologists for locating geological or geomorphological features expressing regional fault or fracture systems, therefore, the satellite images are used for structural analysis of the Chamshir dam area. As well, using the DEM and geological maps, 3D Models of the area have been constructed. Then, based on these models, all the acquired fracture traces data are integrated in Geographic Information System (GIS) environment by using Arc GIS software. Based on field investigation and DEM model, main structures in the area consist of Cham Shir syncline and two fault sets, the main thrust faults with NW-SE direction and small normal faults in NE-SW direction. There are three joint sets in the study area, both of them (J1 and J3) are the main large fractures around the Chamshir dam. These fractures indeed consist with the normal faults in NE-SW direction. The third joint set in NW-SE is normal to the others. In general, according to topography, geomorphology and structural geology evidences, Chamshir dam has a potential for sliding in some parts of Gachsaran formation.

3-D laser imaging of drill core for fracture detection and Rock Quality Designation

The Rock Quality Designation (RQD) is a widely used parameter in empirical methods of estimating rock mass strength. This proof of concept research is a step toward the semi-automatic computation of the RQD and is based on 3-D imaging procedures and algorithms to detect fractures in drill core. The images were acquired with a triangulation-based 3-D laser digitizer. Each image file is a point cloud of spatially referenced measurements in Cartesian space. Variations in the z-coordinate (digitizer-to-target distance) were used to detect fractures in profile. Natural fractures were distinguished from mechanical breaks by measuring the angle, and quantifying the roughness, of the fracture trace. The algorithms use a binary centerline profile to measure intact lengths of core for the RQD calculation. This 3-D approach measures changes in the core surface, not intensity features and shadows as with 2-D photographs. Limitations arise when there is no detectable change in the z-coordinate.

Localization of submicron inclusion re-equilibration at healed fractures in host garnet

Microstructures in Permian inclusion-bearing metapegmatite garnets from the Koralpe (Eastern Alps, Austria) reveal re-equilibration by coarsening of abundant submicron-sized inclusions (1 μm–2 nm diameter) at the site of healed brittle cracks. The microstructures developed during Cretaceous eclogite-facies deformation and the related overprinting of the host–inclusion system. Trails of coarsened inclusions (1–10 μm diameter) crosscut the garnet, defining traces of former fractures with occasional en-echelon overlaps. Trails are flanked by 10- to 100-μm-wide ‘bleaching zones’ characterized by the absence of ≤1-μm-sized inclusions in optical and SE images. FEG-microprobe data show that trails and bleaching zones can form isochemically, although some trails exhibit non-isochemical coarsening. Cross-correlation-based EBSD analysis reveals garnet lattice rotation of up to 0.45°, spatially correlated with bleaching zones. The garnet lattice in the center of trails is misoriented around different axes with respect to the lattice either side of the trail. Elevated dislocation density within bleaching zones is confirmed by TEM observations. Dislocations represent a plastic wake formed by crystal plastic deformation at the crack tip. Fracture enhanced diffusion rates in the lattice adjacent to crack planes by introducing dislocations, priming these areas to behave differently to the bulk of the garnet during Cretaceous metamorphism and facilitating localized coarsening of inclusions. Diffusion within the bleaching zone was enhanced by a minimum factor of 102. The partially closed host–inclusion system records the influence of deformation mechanisms on re-equilibration and contributes to understanding of the interaction between deformation and chemical reaction during metamorphism.

Natural Fractures in shale: A review and new observations

Natural fractures have long been suspected as a factor in production from shale reservoirs because gas and oil production commonly exceeds the rates expected from low-porosity and low-permeability shale host rock. Many shale outcrops, cores, and image logs contain fractures or fracture traces, and microseismic event patterns associated with hydraulic-fracture stimulation have been ascribed to natural fracture reactivation. Here we review previous work, and present new core and outcrop data from 18 shale plays that reveal common types of shale fractures and their mineralization, orientation, and size patterns. A wide range of shales have a common suite of types and configurations of fractures: those at high angle to bedding, faults, bed-parallel fractures, early compacted fractures, and fractures associated with concretions. These fractures differ markedly in their prevalence and arrangement within each shale play, however, constituting different fracture stratigraphies—differences that depend on interface and mechanical properties governed by depositional, diagenetic, and structural setting. Several mechanisms may act independently or in combination to cause fracture growth, including differential compaction, local and regional stress changes associated with tectonic events, strain accommodation around large structures, catagenesis, and uplift. Fracture systems in shales are heterogeneous; they can enhance or detract from producibility, augment or reduce rock strength and the propensity to interact with hydraulic-fracture stimulation. Burial history and fracture diagenesis influence fracture attributes and may provide more information for fracture prediction than is commonly appreciated. The role of microfractures in production from shale is currently poorly understood yet potentially critical; we identify a need for further work in this field and on the role of natural fractures generally.

Direct Bonding Mechanism of ALD-Al2O3 Thin Films

Direct bonding is used to join two mirror-polished wafers without any additional material. This technique demonstrates to be more and more attractive for microelectronics, MEMS, or optoelectronic applications as example. In many of them, Silicon-On-Insulator (SOI) substrate is used including a SiO2 buried layer (BOX). Face to circuit performance request, SOI self-heating in these devices has to be improved, replacing BOX by adapted layers, for instance. The conciliation between the thermal and electrical properties has already pointed out different materials such as diamond, Al2O3, HfO2 or Si3N4 [1]. Atomic Layer Deposited (ALD) amorphous Al2O3 thin film seems to be very interesting but different problems as for instance debonding phenomena [2][3], or defect emergence [4][5][6] could appear during their elaboration which motivated our direct bonding mechanism study. In this work, comparative results between free surfaces and bonding configurations will be done in order to establish bonding behaviour of ALD Al2O3.A bonding mechanism will be discussed and proposed.The study is carried out on 300mm, lightly p-doped Si wafers. Substrates have been oxidized by plasma or thermal treatment in order to create 1.5, 20 or 145nm SiO2 sub-layer. 20 nm-thick amorphous alumina (a-Al2O3) films were then deposited at low temperature (300°C) by ALD using TMA and H2O precursors. Some samples were annealed at various temperatures under nitrogen or oxygen atmosphere in order to crystallize the amorphous alumina. Due to low chemical resistance of the amorphous ALD Al2O3layer, the wafers were just rinsed with de-ionized water under megasonic power, dried and contacted to each other or directly to silicon wafers or oxidised silicon wafers at room temperature (RT) and atmospheric pressure. Bonding quality is analysed at room temperature and after various annealing temperatures.After 400°C post bonding annealing, using scanning acoustic microscopy (SAM), a high defect density is observed for several bonding type (fig 1a) which is invisible using wafer-scale IR observations (fig 1b). In the specific a-Al2O3/a-Al2O3bonding, debonding could even occur after 500°C annealing. Bonded surface analyses exhibit inhomogeneous fracture and bubble traces at the bonding interface (fig 1c).This paper will deal with bonding mechanism and the defect origin. We will highlight the role of water/hydrogen diffusion in the bonding process and the link that could be done with the well-known [4][7] defects which could appear during O2-atmosphere annealing of amorphous ALD Al2O3 free surfaces (fig2a) while no defect are seen under N2annealing (fig2b).Using atomic force microscopy to measure the surface roughness, the electron beam microscopy to visualize the debonding interface, the anhydrous bonding energy measurements, the FTIR-MIR [8] to characterize the chemical interface evolution and the X-ray reflectivity for monitoring the interface electron density profile, all the different bonding structures achieved in this study have been analysed (preannealing, sublayer use…).Based on known SiO2 hydrophilic direct bonding mechanisms [8], refined bonding mechanisms for amorphous a-Al2O3 bonding will be proposed. Therefore, defect free amorphous Al2O3bonding could be obtained overall the post bonding annealing temperature range (RT-1200°C) as shown for 300mm bonded structures (Fig 3).One of the first applications of this work would be the elaboration of high quality SOI structure having this ALD Al2O3layer as an insulating layer. ACKNOWLEDGMENT The authors would like to thank SOITEC for its support. REFERENCES [1] N. Bresson, et al. Solid-State Elect. 49, 1522-1528, 2005[2] P. Ericsson, et al., ECS PV, 576, 1997[3] C. de Beaumont, et al., Electro Soc. 3, 231-236, 2005[4] M. Yokoyama, et al., Semi. Sci. Tech., 28, 2013[5] D. Landru, et al., ECS JSS and Tech, 6, 2, Q83-Q87, 2013[6] E. Beche, et al., Micro Techn (submitted)[7] T. Nabatame, et al., JAP, 42, 7205-7208, 2003[8] C. Ventosa et al., JAP, 104, 2008

Effect of Annealing Temperature on Microstructures and Properties of Warmly Deformed SCRAM Steel

Effect of annealing temperature on microstructures and properties of warmly deformed SCRAM (Super-clean Reduced Activation Martensitic) steel on Gleeble-3500 thermo-simulation machine was investigated. The results showed that an increase in the annealing temperature can result in increasing the martensitic lath width from 0.48 um to 0.65 um and decreasing the dislocation density from 6.4×1015m-2to 2.8×1015m-2in SCRAM steel. The specimen exhibited high reduction of area and total elongations when the annealing temperature is up to 600 oC. The tensile fracture surface observation indicated that dimples became more uniform and deeper and cleavage fracture traces disappeared with the annealing temperature increasing. The irradiation-induced helium bubbles and hardening were observed in all the specimens after helium implantation to 1e + 17/cm2at 450 oC. The helium bubbles became larger but less when the annealing temperature increased. The optimal annealing temperature is 450 oC in this experiment.

Evaluating Surface Cleaning Techniques of Stone Tools Using Laser Scanning Confocal Microscopy

Introduction Stone tool use-wear analysis reconstructs how tools were used in the distant past. This is accomplished through the identification of microscopic traces of polish, striations, and fractures left on the tool’s surface. Use-wear analysis is based on the hypothesis that different contact materials (e.g., wood, wheat, or meat) and different motions (e.g., cutting, scraping, or drilling) produce distinct microscopic traces on the used tool including microfractures, polish, and striations. Understanding the function of tools gives archaeologists insight into the behaviors of past peoples, allowing for the reconstruction of ancient ways of life. Traditional use-wear analysis uses light microscopy to visually identify wear traces [1, 2, 3]. However, this qualitative analysis can lead to interpretive conflicts between researchers. In recent years, new methods for measuring usewear have been developed that quantify functional traces on stone tools [4-12]. Many of these methods quantify the surface roughness of the polished areas, measuring topographic features at small scales to understand variation in surface texture created by contact materials such as antler, meat, and wood. One method that shows particular promise uses a laser scanning confocal microscope (in this case, the OLYMPUS LEXT OLS4000) to characterize surface texture. Outlined here are the results of measurements taken with the above instrument to understand the effects of various cleaning methods on the surface roughness of experimental stone tools used to cut wheat. Currently, there is little consensus among use-wear analysts on how to adequately clean stone tools prior to analysis. Standardization is integral to the development of use-wear analysis and for continued research into the quantification of wear traces as it allows for comparability of the results from different researchers. In the research presented here, experimental stone tools were subjected to three levels of cleaning: (1) with alcohol, (2) alcohol followed by soap and water, and finally (3) chemical cleaning with potassium hydroxide (10%) and hydrochloric acid (10%). These three stages of cleaning represent commonly used techniques of sample preparation and are increasingly invasive. The results of this study contribute to the standardization of sample preparation and show the application of the LEXT OLS4000 for archaeological use-wear studies. This article describes measurements that indicate how different commonly used cleaning protocols affect surface roughness measurements.

Use of Descartes Folium Equation for Deriving a Relation between Total Aperture of Fractures after Uniaxial Compression and Strain Parameters of Different Rocks Exhibiting Negative Total Volumetric Strains

The axial, crack and total volumetric strains, porosity, elastic constants, crack damage stresses, uniaxial compressive strengths, as well as fracture apertures and number of fracture traces in rock samples surface after compression were defined for different chalk, basalt, dolomite, granite, limestone and sandstone samples exhibiting negative total volumetric strain at failure. It is established that the total (summed) aperture of vertical fractures obtained on the lateral surface of rock sample is related to three characteristic strain parameters: axial strain at the onset of negative total volumetric strain, axial failure strain and negative total volumetric strain at failure. The relation is based on Descartes folium equation, where the length of the loop of folium is equal to axial strain coordinate at the onset of negative total volumetric strain. This relation shows that the total aperture increases according to power law with increasing difference between axial failure strain and axial strain at the onset of negative total volumetric strain. Simultaneously, an increase in this difference leads to an increase in the value of negative total volumetric strain at failure. It is found that a direct correlation between total aperture of fractures and negative total volumetric strain at failure is relatively weak. Nevertheless, total aperture of fractures tends to increase with increasing absolute value of negative total volumetric strain at failure. It is revealed that there is no connection between the number of fracture traces and negative total volumetric strain at failure.

Estimation of fracture trace length distributions using probability weighted moments and L-moments

The characterization of fracture trace length distributions is an initial and essential step in estimating three-dimensional fracture size distributions. Present challenge mainly lies in the accurate depiction for the distributional nature of trace lengths from various sizes of trace data, especially for small samples. The present paper is an attempt to solve this problem by using probability weighted moments (PWMs) and L-moments. To quantify the statistical property of trace lengths, the PWMs and L-moments of true trace lengths on an infinite surface from the measured trace lengths by an irregular convex window are estimated. A distribution-free method is then developed using the maximum entropy principle with PWMs for estimating the quantile functions of true trace lengths. Since there is no assumption regarding the type of trace length population distribution, the estimation obtained is distribution-free. For practicing engineers, a method using L-moments for estimating the common trace length distributions is also suggested. Examples that are tested showing the present method provides good approximations of the quantile functions and probability density functions of true trace lengths. The method is effective even for problems with outliers or highly skewed trace data, and can be used as a reliable tool for inferences from various sample sizes with good accuracies.