Gravel Particles Research Articles

Roadbed continuous compaction quality testing and settlement difference detection "dual control" practice and methods

The continuous compaction quality testing technology of roadbed is disturbed by many external factors, and improving the accuracy of testing is the key link of construction quality control. With the background of a reclaimed soil roadbed project, the test method for continuous compaction quality control of roadbed was formulated, including the compaction testing test section division and the combination of rolling number of passes as well as the "dual-control" process system; the linear relationship between the VCV value and the sand filling method of compaction testing was verified; the GPS elevation data were compared with the sand filling method to determine the compaction level. 22.264, correlation coefficient R=0.8781; through the analysis of variance between GPS elevation data and measured elevation data, the stability of GPS automatic elevation data is determined, and the test data proves that the characterization of roadbed compaction by settlement difference value and VCV detection value has good consistency, and that "dual control" of settlement difference method and VCV value is reasonable. "is reasonable, and gives the 96 area sandwiched with gravel particles of dry stiff clay fill soil roadbed rolling reasonable total number of times for 9 times, VCV reasonable threshold value of 65.30.

Separation of sand and gravel particles in volume images using a random forest

Geometric features of sand and gravel particles contained in building materials significantly influence the macroscopic properties of the final structure. Investigating volume images of these particles acquired by micro-computed tomography is of interest, as all features are then directly derivable. However, particles touch and must be separated in the 3D image before being analyzed. For multi-sized and strongly non-spherical particles, there is no standard solution for this task available. We first separate the particles by the established morphological procedure of applying the watershed transform marked by the minima of the inverted distance map, here with the notorious over-segmentation alleviated by pre-flooding. Subsequently, remaining errors – particles split into several fragments – are detected by a random forest and automatically united. Training on one to two 3D images, only, we achieve accuracies rendering the currently still necessary manual correction obsolete. More precisely, less than 3% of the particles of natural origin including crushed ones remain incorrectly segmented. Even more remarkable is the result for recycled materials, where the final rate of wrongly segmented particles does not exceed 6%.

Developing Liquefaction Prediction Equations for Gravels Based on DPT Blow Count and Shear Wave Velocity at Field Case History Sites

Gravelly soils have liquefied at multiple sites in at least 20 earthquakes over the past 130 years. These gravels typically contain more than 25% sand which lowers the permeability and makes them susceptible to liquefaction. In other cases, a low permeability layer at the surface impedes drainage and causes liquefaction. Typical SPT- or CPT-based liquefaction correlations can be affected by large gravel particles and lead to erroneous results. To deal with these problems, we have developed liquefaction triggering curves for gravelly soils based on (1) shear wave velocity (Vs) and (2) a 74-mm diameter dynamic cone penetrometer (DPT), that are less affected by gravel particles. These correlations are based on case histories where gravel did and did not liquefy in past earthquakes. The VS-based liquefaction triggering curves for gravels shift to the right relative to similar curves based on sands. Good agreement has been obtained with liquefaction resistance from the DPT and the CPT when these methods could all penetrate the gravel in Wellington New Zealand. Correlations are developed between Vs and blow count from the DPT.

Refined evaluation approach for geometrical, physical and chemical properties of completely decomposed tuff soil particles

This paper presents a refined approach for evaluating the geometrical, physical, and chemical properties of weathered soil particles and illustrates it with a completely decomposed tuff (CDT) soil. This refined evaluation approach consists of two parts. Part I separates soil into 25 sub-groups of gravel, sand, silt, and clay particles from 14 mm to less than 0.0008 mm by washing and sieving. Part II applies laboratory tests to examine the refined geometrical, physical, and chemical properties of each sub-group of materials. These laboratory tests include the dynamic and static image analysis for particle shape evaluation, the Atterberg limits test for plasticity evaluation, the falling head permeability test for hydraulic conductivity evaluation, the energy dispersive X-ray spectrometer (EDS) test and X-ray fluorescence spectrometer (XRF) test for elemental composition evaluation, and the X-ray diffractometer (XRD) test for mineral composition evaluation. The quantitative results of these refined properties of the soil materials can be expressed as a function of the particle size. The characteristics of each sub-group of particles together determine the properties of the soil mixture. This refined evaluation approach provides a new insight for examining the properties of weathered soils and their weathering degrees.

Grain-size composition effect on flexural response and pore structure of cementitious tail-rock fills with fiber reinforcement

This paper explores the grain-size composition effect on flexural and micro-structural features of fiber reinforced cementitious tail-rock fill (FRCTRF). The FRCTRF mixes considered contained a stationary solid concentration of 70 wt% and a cement/tail rate of 1:6, and were cured for an age of 7-day for strength tests and microstructure. Three-point bending test shows that FRCTRF’s bending property is upgraded by totaling gravel rock. Adding fiber to FRCTRF’s bottom can enhance its peak deflection. With rising gravel particle size/dosage, FRCTRF’s peak deflection displays a trend of falling first and then growing. Accumulating polypropylene fiber could advance FRCTRF’s post-peak strength features as well. FRCTRF sample containing gravel has a large stress drop, and adding gravel rock could essentially boost FRCTRF’s post-peak brittle-ability. In conclusion, this study provides a strong scientific and theoretical underpinning for optimizing artificial false roofs employed recently in modern underground metalliferous mining operations.

Study on the resistance of basalt fiber concrete to erosion of building structure by wind gravel flow

Concrete structures in the windy regions of the Gobi face constant erosion from wind gravel flow, leading to severe surface damage and significantly reduced durability. This paper investigates the erosion resistance of basalt fiber (BF) concrete under various erosion conditions using the air-flow sand injection method. The results indicate that adding 0.15 % BF to concrete reduces its erosion rate by 20.7–21.5 % compared to concrete without BF. Therefore, a BF content of 0.15 % (BF15) provides optimal erosion resistance for the concrete. The correct amount of BF bonds tightly with the cement mortar, forming a mesh structure inside the concrete that absorbs the kinetic energy of gravel impacts. The concrete erosion process can be divided into an early accelerated phase and a later stabilized phase. Throughout these phases, the erosion rate of concrete increases with the erosion angle (EA), erosion wind speed (EWS), and gravel flow rate (GFR). In particular, the erosion rate of BF15 concrete increased by 35.6–46.4 mg/cm² when the EA changed from 15° to 90°. Notably, surface damage from low-angle erosion mainly consists of cut scratches, while high-angle erosion primarily results in erosion pits. As the grain size of the eroded gravel increases, the erosion rate of the concrete decreases. However, when a single large gravel particle impacts the concrete, it creates a larger and deeper erosion pit. Furthermore, the erosion rate of BF concrete exhibits a strong negative linear correlation with its mechanical properties, with an R² value exceeding 0.88. Moreover, erosion reduces both compressive and splitting tensile strengths of concrete. For BF15 concrete, however, the decreases are minimal: compressive strength drops by just 1.2 MPa, and splitting tensile strength decreases by only 0.2 MPa. Building on Bitter and Neilson’s theoretical erosion model, an improved erosion model for BF concrete has been developed under wind gravel flow. This model incorporates the BF mixing factor and particle size function while considering other erosion parameters comprehensively. The enhanced model provides a theoretical foundation and scientific basis for safeguarding concrete structures in Gobi wind-prone regions.

Image processing and neural network technique for size characterization of gravel particles

Particle size is considered one of the significant characteristics used in geotechnical practices. Traditionally, sieve analysis is utilized for coarse-grained soil. However, this method could be time consuming and take much effort, especially for large scale infrastructure projects. This paper presents an efficient method for estimating gravel particle characterization utilizing image processing and artificial neural network technique (IPNN). The proposed algorithm is performed by utilizing particle boundary delineation and shape feature extraction to train a neural network model for estimating gravel size distribution curve. It is found that excellent agreement exists between the results obtained from conventional sieve analysis and neural analysis for gravel soil particles with maximum difference in passing percentages up to only 3.70%. The proposed technique shows satisfactory results for crushed stone samples with maximum difference in passing percentages about 10.90% mainly in large diameter particles. The presented technique (IPNN) could offer a promising alternative technique for material quality control process especially in large scale projects.

Estimating the compacted dry density of gravelly soil with oversized particles

The compacted dry density of gravelly soils containing particles that are too large for ordinary laboratory compaction tests is usually estimated by measuring the dry density of the base sample obtained by removing over-sized particles then correcting the measured value by the Walker-Holtz Equation (W&H Eq.). It is known that the W&H Eq. overestimates the dry density of gravelly soils and this trend becomes stronger as the mass ratio P of oversized particles increases. It seems that a satisfactory solution is not yet available. A comprehensive series of laboratory compaction tests was performed on a wide variety of gravelly soil samples with different particle sizes, grading uniformities and particle shapes. The followings were found. The ratio, X, of the maximum dry density predicted by the W&H Eq. to the measured value increases linearly from unity as P increases from zero up to approximately 0.75. The slope of the X-P relation, (X − 1.0) / P, increases as the coefficient of uniformity or the fines content of the base sample increases and as the gravel particles become more angular in a synergistic manner. It is proposed to estimate the maximum dry density of compacted gravelly soil containing oversized particles by dividing the value predicted from the W&H Eq. by X obtained from the substitution of P into the relevant X-P relation. Proposed based on the above is an effective and efficient compaction method for gravelly soils containing oversized particles that controls the degree of saturation and the compaction energy.

Influence of fines and gravel particles on strength-dilatancy of river sand: Effect of depositional conditions

Understanding the effects of low plastic fines and gravel contents on the mechanical behavior of sandy soils in terms of the strength-dilatancy relationship is crucial for various geotechnical applications. To gain deeper insights, an extensive series of direct shear tests were performed on two distinct types of mixtures: sand-fines mixtures and sand-gravel mixtures. The study systematically varied Fc/Gc content from 0% to 30%, using dry and wet methods, at a medium density (Dr = 50%) and a range of normal stresses (σn = 100–300 kPa). The experimental findings provide remarkable trends. For dry pluviated specimens, an increase in fines content led to a decrease in the shear strength of the mixtures. Conversely, the wet deposited specimens exhibited an opposite tendency, where higher fines content induced larger shear strength. Notably, the incorporation of gravel substantially improved the mechanical performance of the sand mixtures, regardless of the preparation method employed. Dry pluviated specimens generally exhibited higher shear strength than that of the wet deposited ones for the same Fc/Gc. A developed set of equations has been suggested to predict the strength-dilatancy relationships for all-tested materials. These equations take into account the impacts of fines and gravel contents and both specimen preparation methods.

Fluvial fan sedimentary characteristics of distributive fluvial system

The characteristics of fan sediment in the distributive fluvial system are evaluated based on a thorough analysis of modern silt in the Guertu river distributive fluvial system, as well as data obtained from UAV aerial photography and satellite remote sensing. The Guertu River Distributive Fluvial System (DFS) is classified into three stages, namely "proximal," "middle," and "distal," based on the examination of river morphology, sediment variations, sedimentary attributes, and other relevant aspects throughout different sections of its tributaries, from the source to the mouth. At the upstream section of the downstream fining sequence, the slope is the steepest and the hydrodynamic conditions are intense, resulting in the formation of a predominantly big gravel braided river. The river bed section has a morphology resembling a combination of a "V" and a "U" shape. It is characterized by a narrow and deep configuration, with a relatively short breadth. The sediment primarily consists of medium to large-sized gravel with minimal sand content. The gravel exhibits good roundness and displays a considerable degree of orientation. The primary microfacies present are braided channel and flood plain. The slope of the central area is decreased in comparison to the nearby end, primarily due to the presence of extensive braided rivers. The river bed has a greater width, with minor eolian dunes visible in the river channel. The gravel particles are predominantly fine to medium in size, and there is an increased amount of sand present. The predominant microfacies are braided channels, floodplains, and eolian dunes. At the distal end, the slope is minimal, the landscape is level, the braided river transitions into a meandering river, the sediment consists primarily of sand, and the signs of bioturbation are clearly visible. The primary microfacies consist of braided channels, meandering channels, floodplains, eolian dunes, lakes, and swamps.

Study on the relationships between particle shapes and motion responses in the geotechnical coarse-grained system subjected to vibration loads

The vibration-induced deformation of coarse-grained soil originates from the internal particle motions, which are reflected in translational and rotational behaviors controlled by particle shapes. However, the mechanism by which particle shapes affect particle motions in granular systems remains unclear, and diverse shape parameters make it difficult to accurately express the motion behaviors through a single shape parameter. Leveraging the advantages of the discrete element method (DEM) and machine learning methods, therefore, the relationships between shape features and motion behaviors were explored in complex-shaped granular systems. Firstly, a shape database containing hundreds of gravel particles was constructed, from which 10 representative shape parameters were selected to characterize the Form, Sphericity, and Roundness features through hierarchical clustering and principal component analysis. Then, three DEM models, established based on the shape database, were simulated to obtain particles’ translational and rotational indicators. Following, a regression relationship between representative shape parameters and motion indicators was established through the XGBoost model, and the SHAP values were utilized to explore the main shape parameters influencing particle motions. The results indicate that particle motions in the upper layer are primarily influenced by the Form parameter, and the equiaxial shape can promote the vertical displacement. The particle motions in the middle layer are mainly controlled by the Sphericity and Roundness parameters, and the flatness or angular shape has a suppressing effect on the vertical displacement.

Impact of initial gradation on compaction characteristics and particle crushing behavior of gravel under dynamic loading

Gravel is a widely used construction material due to its versatility and cost-effectiveness. However, gravel particles are prone to crushing under dynamic loading, causing changes in gradation. The evolution of gradation and its effects on physical properties are not well understood. This study investigates the physical properties of gravel, such as dry density, void ratio, and relative crushing index, under different initial gradations (uniformity coefficient, Cu), using surface vibration compaction tests. A hyperbolic relationship was established between initial Cu and dry density, showing that an increase in Cu can result in a decrease in the void ratio and an increase in the coordination number until stabilization. Particle crushing increases with higher initial Cu, correlating quantitatively with relative crushing indexes. Maximum dry density, minimum void ratio, and fractal dimension also correlate with these relative crushing indexes, suggesting intrinsic relationships among these properties and particle crushing. The size effect can be eliminated by establishing empirical relationships between crushing parameter and particle size.

Particle shape analysis of calcareous sand based on digital images

Particle geometric is a key parameter that defines the eometric attributes of calcareous sand particles and is intricately related to their mechanical traits, such as compression and shear. The scanning electron microscopy and digital imaging were applied to capture the microscopic properties and geometric projections of calcareous sand. The qualitative analysis, conventional statistical methods and fractal theory were employed to describe the geometric morphology of sand particles. Additionally, we analyzed the structural and physical traits of calcareous sand based on its unique biological genesis. We developed a hypothetical structural-physical model for calcareous sand. Our findings revealed the interwoven reticulation on the surface of calcareous gravel particles, along with an uneven distribution of pores on the external surface. As the particle size increased, the global profile factor decreased and the angularity increased. The critical threshold for the variations in flatness, surface roughness, and circularity was observed at a particle size of 5 mm, with the particle size having a relatively minor effect on these characteristics for particles smaller than 5 mm. The shape of the calcareous sand particles exhibited fractal characteristics, with fractal dimension serving as a measure of surface smoothness, particle breakage, and strength. These experimental results could significantly enhance our understanding of the mechanical behavior of calcareous sand.

Experimental Study of Scouring and Deposition Characteristics of Riprap at Embankment Toe Due to Overflow

In this study, the effects of the grain size and gradation of riprap, the overtopping flow depth, and the downstream slope of the embankment on the scouring and deposition characteristics at the downstream toe of the embankment were investigated. For the experiment, three different downstream slopes (1:2, 1:3, and 1:4), three different overflow depths (1, 2, and 3 cm), and three different sizes of riprap particles (d50 of 16.41 mm, 8.48 mm, and 3.39 mm, herein referred to as coarse gravel, medium gravel, and granule, respectively) were used in the laboratory. The experimental results demonstrated that the scour depth and deposition height increased with increasing energy head for each downstream slope condition. Among the three particle sizes, coarse gravel shows the lowest scour depth and the highest deposition height. For the 1:2 slope, the coarse gravel particle size was 62% and 75% less resistant to scouring than the medium gravel and granule particles, respectively. For the 1:3 slope case, this was 31% and 46%, and for the 1:4 slope case, this was 39% and 49% less than the medium gravel and granule size particles, respectively.

Micro-cracks evolution process and borehole stability analysis in deep pebbly sandstone based on THM coupling method

The heterogeneity of pebbly sandstone is strong due to the random distribution of gravel particles, resulting in unique mechanical behaviors and failure patterns under high temperature and high pressure. It poses significant challenges to exploring and developing oil and gas resources in deep pebbly sandstone reservoirs. Thus, to investigate the impact of high pressure, high temperature, and gravel distribution on the strength characteristics and failure patterns of pebbly sandstone, based on typical samples from the Tarim Basin, a numerical model that accurately represents the distribution of gravel particles in pebbly sandstone was built. Lastly, a Thermo-Hydro-Mechanical coupling model for pebbly sandstone boreholes was established to quantify the influence of the difference coefficient of in-situ stress and gravel volume fraction. The results show that during the rupturing process of pebbly sandstone, the micro-cracks initiation occurs and expands around the gravel, forming a shear-type fracture. At the same time, several secondary cracks are formed inside the rock. With increasing confining pressure, the number of secondary cracks decreases. The fracture morphology is complex in concentrated gravel distribution, whereas a single fracture dominates the failure pattern in uniform distribution. The micro-cracks are more likely to occur in the gravel areas around the borehole during drilling, resulting in the gravel accumulation areas prioritizing collapse rather than in the direction of minimum horizontal in-situ stress, significantly reducing the safe density window. The safety density window decreases with the increase of the gravel volume but increases when the gravel volume fraction is higher than 20%. The research results provide valuable guidance for efficient and safe drilling in pebbly sandstone formations.

Impact of roots on the shear strength of root-reinforced soil on slopes

Abstract Tropical countries generally receive high rainfall throughout the year causing high runoff, wet soils and erosion. Undulating terrain from continuing erosion and frequent occurrences of landslides are the features of topographic evolution under such hydrological conditions. Vegetation is the only natural supporting factor that mitigates both erosion and landslides. It contributes to controlling soil erosion and strengthening of the soil by forming a mesh of roots at the surface. The objective of this study is to quantify soil strength on slopes when there is a presence of roots. Undisturbed samples were taken from two different depths of soil. The exact depth and distance varied slightly to avoid large roots and large gravel particles present in the natural environment. Immediately after sampling, the triaxial tests were performed under unconsolidated and undrained conditions. Subsequently, the tested samples were crushed carefully, to manually recover all roots and to classify the soil. From this study, it was observed that the presence of root fibres within the soil matrix has enhanced the soil strength through a binding action in the fibre-soil composite. The correlation between root content and shear strength is prominent near the surface and becomes less obvious in deeper soil layers when the root concentration becomes more sparsely distributed.

Study on the Effect and Enhancement of Near-Natural Integrated Plant Positioning Configuration in the Hilly Gully Region, China

The establishment of protective forests plays a crucial role in mitigating soil erosion on slopes within hilly and gully regions. However, in practical applications, the configuration of protective forests on slopes is intricate and diverse, and the suitability and rationality of different configuration patterns for various slope sections have not been thoroughly investigated. This study focuses on a 40-year-old artificial protective forest, examining 16 different configuration patterns on the top, middle, and lower slopes. It compares the growth conditions, community structure stability, and characteristics of the saturated soil’s hydraulic conductivity. The findings indicate that the top slope should be identified as a critical area for slope protection. The optimal configuration for this area is the “tree + grass” pattern with a spacing of 5 m × 5 m, which promotes the optimal growth of tree species and effectively reduces the surface runoff of gravel particles ranging from 1 cm to 3 cm in diameter. On the middle slope, the “tree + shrub + grass” structure proves effective in slowing down the erosive force of slope runoff. The recommended spacing for trees is 5 m × 6 m, and for understory shrubs, it is 1 m × 6 m. This configuration pattern results in the most stable structure for the plant community and maximizes the water conservation potential of forest litter. By analyzing the characteristics of the saturated soil’s hydraulic conductivity, we find that the complexity of the plant configuration on the lower slopes is correlated with a greater coefficient of variation in the saturated soil’s hydraulic conductivity. Nevertheless, there is no significant difference in the average soil saturated hydraulic conductivity per unit area between the different configuration patterns. Consequently, the lower slope can rely on the natural recovery of herbaceous plants. The results of this research contribute valuable scientific and technical insights to the management of soil erosion in hilly and gully areas, both in China and around the world.

Accounting for the power of nature: Using flume and field studies to compare the capacities of bio‐energy and fluvial energy to move surficial gravels

AbstractRiver channels, riparian and floodplain forms and dynamics are all influenced strongly by biological processes. However, the influence of macroinvertebrates on entrainment and transport of river sediments remains poorly understood. We use an energy‐based approach to explore the capacity of benthic animals to move surficial, gravel‐bed particles in field and laboratory settings and use the results to assess the relative significance of biological and physical benthic processes. Our results showed that in 11 British gravel‐bed rivers, the maximum energy content (i.e., calorific content) of macroinvertebrate communities generally matched the flow energy associated with median discharges and, at multiple sites, exceeded that of the 10‐year return interval flood. A series of laboratory experiments used to estimate the minimum energy expended by signal crayfish (Pacifastacus leniusculus) when performing geomorphic work established that crayfish move gravel particles at energy levels below that expected of the flow, complicating direct comparisons of the capacity for macroinvertebrates and fluvial flows to influence bed mobility. Our findings suggest that the influence of macroinvertebrate communities in either promoting or suppressing, the mobilisation of the bed may be large compared to equivalent values of fluvial energy. Based on these findings, we conclude that in the gravel‐bed rivers studied, the macroinvertebrate community's potential to perform geomorphic work matches or exceeds the stream power during most of the year. Although our study examined biological and fluvial energy systems separately, it is important to recognise that in nature, these systems are highly interactive. It follows that utilising the energy framework presented in this paper could lead to rapid advances in both fluvial biogeomorphology and river management and restoration.

Real-time evaluation of the blending uniformity of industrially produced gravelly soil based on Cond-YOLOv8-seg

Industrial production of gravelly soil has been applied at construction sites in earth-rock engineering, which adopts automatic blending and belt-conveyer systems for gravelly soil. The blending uniformity of gravelly soil has a significant impact on its mechanical and physical properties including shear resistance and impermeability. Real-time evaluation of blending uniformity is key to controlling the quality of gravelly soil. This study proposes a real-time evaluation method for the blending uniformity of gravelly soil transported by a belt conveyor. First, Cond-YOLOv8-seg is adapted to accurately segment gravel particles from gravelly soil images, employing a conditional convolution segmentation head and an improved Protonet embedded with a recurrent criss-cross attention (RCCA) module based on YOLOv8-seg. Then, the segmented masks are used to analyze the spatial uniformity (SU) and blending ratio consistency (BRC) of individual and continuous gravelly soil images, employing the proposed evaluation criterion for SU based on the theory of deformable four-sided static distances and BRC based on the area ratio of different-scale gravel particles in one image. Cond-YOLOv8-seg achieved an AP50 of 0.803 and FPS of 58.3. The effectiveness of the proposed evaluation criteria is validated quantitatively. The average uniformity evaluation time of a 2048 × 1536 image is determined to be 0.1151s, which is close to the real-time evaluation of gravelly soil transported by a belt conveyor.

The dominant mineralogical triggers hindering the efficient development of the world's largest conglomerate oilfield

In the complex fluid environment of subterranean rocks, some mineral components are easily hydrated, which hinders the accumulation and utilization of hydrocarbon. However, the nature and distribution of these key substances remain unclear. This study aims to provide a fresh perspective on the substances that impede the storage and extraction of hydrocarbon of the world's largest conglomerate oilfield. Using a variety of qualitative, semi-quantitative, and quantitative methods, including X-ray diffraction, secondary electron imaging, elemental spectroscopy, and Tescan-Integration-Mineral-Analyzer (TIMA), our experimental results show: (1) For the first time, water-sensitive clay minerals on the surfaces of gravel particles in tight conglomerates in China have been identified. Although the matrix composition contains less than 4.2% clay minerals on average, certain gravels contain over 72.7% clay minerals. These clay minerals are primarily composed of smectite, which is highly water sensitive, followed by chlorite, which poses significant challenges to hydrocarbon extraction; (2) The distribution of clay minerals on a single gravel surface is relatively uniform, enabling their interaction with fracturing fluid and exacerbating reservoir degradation. The total content of the illite-smectite mixture in the conglomerate can reach approximately 12%, with skeleton particles (gravel) containing more than 30% of this mixture. There are significant differences in the degree of clayiness among different types of gravel, which can be classified as high clayey, medium clayey, or low clayey. The evenly distributed illite-smectite mixed layer on the gravel surface allows complete contact with the fracturing fluid, resulting in severe reservoir damage; (3) Gravel particles with a size range of 8.88 μm–10.73 μm contain the highest concentration of illite-smectite mixture, which is identified as a major factor contributing to reservoir damage.