Soil Grain Size Distribution Research Articles

Determination of average growth rate based on statistical relationships using geomorphological and geotechnical variables in predictive debris flow simulations

Growth rate is a crucial constituent parameter for determining basal entrainment rates in debris flow numerical modeling frameworks. This study presents the development of a multiple-regression model to estimate site-specific average growth rates in advance of debris flow event occurrences. A range of geomorphological and geotechnical variables influencing entrainment was selected through an in-depth literature review. A comprehensive dataset from 35 debris flow events in the Gyeonggi province of South Korea was employed to identify statistically significant variables related to the average growth rate. Through correlation analysis, three variables were ultimately applied as predictors for the multiple regression analysis: channel path length, basin area with slope inclinations of 30 % or greater, and median of soil grain-size distribution. The proposed model was statistically validated by demonstrating high coefficients of determination and meeting key assumptions of no-multicollinearity, no-autocorrelation, normality, and homoscedasticity. In a case study of a historical debris flow event that occurred during the 2011 Mt. Woomyeon landslide disaster, the practical relevance of the developed model was tested by comparing two parallel simulation results using the DAN3D numerical model. Different average growth rates were applied to the two parallel simulations, respectively; the target average growth rate calculated using field-measurement data and the predicted average growth rate derived by applying the multiple regression model. The results revealed that the proposed model provided reasonable predictions of debris flow velocities and heights, with only minor discrepancies between the target and predicted average growth rates. Notably, measured average growth rates of immediately adjacent debris flow events significantly differed from that of the case study event. This highlights that adopting entrainment data from neighboring events for debris flow simulations can result in significantly erroneous debris flow hazard predictions. Finally, the limitations and contributions of this study and future research directions are discussed.

Effect of Grain Size Distribution of Soil on Immobilization of Cadmium and Nickel in Contaminated Soil Using Nano Zerovalent Iron: A Factorial Design and Response Surface Methodology Approach

Urban soils get contaminated due to the unscientific disposal of industrial effluents and solid waste, contaminating the soil with heavy metals. Contaminated soils need to be remediated to avoid the ingestion of toxic heavy metals. The immobilization of heavy metals is one of the methods to remediate contaminated soils. The primary purpose of this study was to explore the effect of grain size distribution (GSD) of soil on the efficiency of immobilization of toxic heavy metals in soil when nano zerovalent iron (nZVI) is used to immobilize the metals. Preliminary studies conducted with the 23 factorial design method confirmed that GSD is a significant factor along with the level of contamination and nZVI dosage in the immobilization of heavy metals in soil. Experiments were conducted with cadmium (Cd) and nickel (Ni), the toxic heavy metals, and three soils with different finer particles than 75 µm. Immobilization efficiency was obtained by comparing the leachability of contaminated and treated soil samples using the toxicity characteristic leaching procedure. Reduction in available fraction and variation in the speciation of heavy metals was observed through the sequential extraction procedure. The response surface methodology was adopted for analysis with three levels of GSD, contamination, and nZVI dosage. For Cd, a reduced cubic model was the best fit with a coefficient of determination (R-square) of 0.93, and for Ni, a quadratic model was the best fit with an R-square of 0.92. Both these models were validated experimentally. The efficiency variation followed an optimum curve concerning GSD, contamination level, and the nZVI dosage. For multimetal contamination, the immobilization efficiency gradually decreased from 10% finer to 90% finer soil, both in the case of Cd and Ni. It was observed that for both single metal and multimetal contamination, the interaction between soil and the nZVI plays a vital role in immobilization along with the factors considered.

Micro–composition evolution of the undisturbed saline soil undergoing different freeze–thaw cycles

The micro–composition of the soil is closely related to its engineering properties. In Northeast China, seasonal freezing and thawing can induce deterioration of the physicomechanical characteristics of saline soil, which can ultimately lead to engineering failures and geological disasters. To investigate the micro composition evolution including the microstructure and grain size distribution of saline soil under the influence of freeze–thaw cycles, mercury intrusion porosimetry (MIP) and laser particle size analysis (LPSA) were used to test undisturbed saline soil specimens undergoing different freeze–thaw cycles. The pore size distribution curves showed a double–peak shape and the grain size distribution curves showed a bidirectional change. Overall, the pores >0.4 μm increased while the pores smaller than 0.4 μm decreased with increasing freeze–thaw cycles. Moreover, the grain size distribution showed a different changing trend at a pore diameter of approximately 10 μm. During the whole freeze–thaw cycle process, the fragmentation of coarse particles (> 10 μm) and the aggregation of fine particles (< 10 μm) were evident, causing the transformation of different pore sizes, and the bidirectional change existed synchronously in the whole process. The freeze–thaw cycles for saline soil caused the lyotropic salt precipitation and dissolution and the ice volumetric expansion and ice segregation to change the grain size distribution leading to the evolution of pore distribution, ultimately changing the soil micro–composition and resulting in the change of macro engineering characteristics. The study is useful for understanding the change in the engineering properties of saline soil under freeze–thaw cycles from a microscale perspective.

An evaluation of topsoil carbon storage in Chinese deserts

Deserts are important components of the terrestrial ecosystem, and significantly affect the terrestrial carbon cycle. However, their carbon storage is poorly understood. To evaluate the topsoil carbon storage in Chinese deserts, we systematically collected topsoil samples (to a depth of 10 cm) from 12 deserts in northern China and analyzed their organic carbon storage. We used partial correlation and boosted regression tree (BRT) analysis to analyze the factors influencing the spatial distribution of soil organic carbon density based on climate, vegetation, soil grain-size distribution, and element geochemistry. The total organic carbon pool of Chinese deserts was 4.83 × 108 t, the mean soil organic carbon density was 1.37 ± 0.18 kg C m−2, and the mean turnover time was 16.50 ± 2.66 yr. With the largest area, the Taklimakan Desert had the highest topsoil organic carbon storage (1.77 × 108 t). The organic carbon density was high in the east and low in the west, whereas the turnover time showed the opposite trend. The soil organic carbon density was >2 kg C m−2 in the four sandy lands in the eastern region, and was greater than the values for the eight deserts (0.72 to 1.22 kg C m−2). Grain-size (i.e., the silt and clay contents) had the strongest influence on the organic carbon density in Chinese deserts, followed by element geochemistry. Precipitation was the main climatic factor that affected the distribution of organic carbon density in the deserts. Based on climate and vegetation cover trends during the past 20 years, Chinese deserts have a high potential for future organic carbon sequestration.

Recent developments in design criteria for granular and geotextile filters

Granular and geotextile filters are commonly provided in several hydrological infrastructures to limit soil erosion and allow unimpeded water seepage. The success of a filter depends on forming a bridging structure, which is governed by the grain size distribution of soil and the constriction size distribution of filter. Currently, the retention requirement is satisfied considering representative grain and opening size, whereas the hydraulic conductivity requirement is satisfied considering empirical factors for avoiding excessive clogging. In this paper, the design criteria for granular and geotextile filters are reviewed, and improved design criteria are presented. A probabilistic retention criterion is developed, considering the grain size and constriction size as random variables. The influence of filter thickness is incorporated into the criterion by considering the number of constrictions in a filtration path. A hydraulic conductivity criterion is developed theoretically based on governing flow equations and the expected partial clogging of geotextiles. The limit states for the developed criteria are evaluated based on the wide range of experimental data. The developed design criteria are applicable to granular and nonwoven geotextiles, which offers an improvement in design compared to the existing criteria in practice.

Pore network modeling approach for simulating soil water retention curve under different stress conditions

The field of unsaturated soil mechanics has recently seen the introduction of pore network models, which attempt to replicate the void structure of porous materials. They are robust physically-based simulation tools and have been used to simulate constitutive relationships like soil water retention curves (SWRC) and unsaturated hydraulic conductivity functions. This work aims to present a pore networkmodeling approach for predicting hysteretic SWRC at various stress states using only grain size distribution and porosity data of the granular soils. The soil sample subjected to given stress conditions is simulated using the Discrete Element Method to obtain a stable packing of spherical particles representing the soil structure. From this packing, an algorithm based on the medial axis is availed to extract a network of pores and throats that describes the geometry and topology of the void structure of the granular soils. Various pore-scale mechanisms like the piston-like advance, corner flow, pore body filling, and snap-off are then used to model fluid displacements at the pore scale to simulate SWRC along the drying and wetting paths. The modeled SWRC under various stress conditions is compared with the measured curves obtained for granular soils from the literature, and the predictions are in good agreement with the experimental results.

Fractal features of soil grain-size distribution in a typical Tamarix cones in the Taklimakan Desert, China

Tamarix cones play key roles in preventing sand erosion and maintaining regional ecosystem stability. This study aimed to explore the characteristics of soil grain size distribution (GSD) in Tamarix cones across the Taklimakan Desert, verify the relationships between soil grain composition and the fractal dimension, and analyze the relationships between soil GSD and environmental factors. Soils of the Tamarix cones from 0 to 500 cm soil depth were sampled every 20 cm at four sites (Qiemo, Qira, Aral, and Tazhong) along the periphery to the hinterland of the Taklimakan Desert. A total of 300 soil samples were collected to measure soil grain sizes and soil properties. Soil grain size composition was dominated by silt and very fine sand, and the fraction of fine particles decreased and that of the coarse particles increased with soil depth, except for at Tazhong. This suggested that suspension-size particles are the main component of the soil GSD and decrease with the increasing depth in the profiles at the Tamarix cones. The soils were poorly and moderately poorly sorted. Kurtosis generally showed a mesokurtic peak, and the GSD was negatively skewed towards the coarser particles. The fractal dimensions of GSD decreased in the following order Qiemo (2.30) > Qira (2.07) > Aral (1.99) > Tazhong (1.96) because of the increase of coarse particles. The fractal dimension had a strong positive correlation with the clay and silt fractions, and a strong negative correlation with the sand fraction, indicating that the fractal dimension can reflect the characteristics of the soil GSD. The strong relationships between the fractal dimensions and selected soil properties indicate that the fractal dimension can not only quantify changes in soil properties, but also reflect the degree of desertification and degradation in the desert region. Considering the strong wind activities and different deposition sources in the Taklimakan Desert, this study provides a deep insight into the soil formation processes of Tamarix cones within extreme arid desert ecosystems.

Improved design criteria for nonwoven geotextile filters with internally stable and unstable soils

In geotextile filtration, the soil fines are either accumulated near the interface, clogged, or washed out, which primarily depends on the grain size distribution (GSD) of soil and the constriction size distribution (CSD) of geotextile. Also, the movement of fines significantly affects the flow capacity of geotextile. Currently, the retention requirement is satisfied based on representative grain and opening sizes, whereas the hydraulic conductivity and clogging requirements are satisfied considering the properties of virgin geotextile. This paper presents a probabilistic retention criterion considering the grain and constriction sizes as random variables. The influence of geotextile thickness is incorporated into the criterion by considering the number of geotextile constrictions in a filtration path. A theoretical approach to predict CSD is presented if the measured data is unavailable. For hydraulic conductivity and clogging requirements, a criterion is presented considering the expected partial clogging of geotextile, which is predicted based on the semi-analytical approach. The limit states for the developed criteria are evaluated based on the wide range of experimental data from the current study and published literature. The developed design criteria are applicable to internally stable and unstable soils, which offers an improvement in design compared to the existing criteria in practice.

Sand Soil Image Processing Using the Watershed Transform and Otsu Thresholding Based on Gaussian Noise

Image processing technology is one of the technologies that can help facilitate and speed up human work, especially in the process of determining the grain size distribution of soil in a civil building plan. Its utilization has been widely used to study, analyze, and understand the structure and framework of the soil. Image analysis is carried out as an initial or fundamental step in image processing to discover and comprehend information. With so many image segmentation methods, it is necessary to conduct research to determine which method is best for sandy soil image segmentation based on one of the image segmentation quality criteria, namely gaussian image noise. By testing the watershed transform method and the Otsu thresholding method as two of the area-based methods that are considered suitable for segmenting sandy soil images before and after distorted Gaussian noise based on the calculation of the mean square error (MSE) value.The results showed that the watershed transform method is better for segmenting sandy soil images when compared to the Otsu thresholding method. This is indicated by the average squared error (mse) of 3.08 for the watershed transform method and 4.09 for the Otsu Thresholding method. In addition to the comparison of quality tests of sandy soil based on gaussian noise with standard deviation values of normal distribution and noise intensities of 10, 20, and 30, it proves that the watershed transform method is still better at segmenting noise-distorted sandy soil images than the Otsu thresholding method. However, in terms of processing time, the Otsu Thresholding method is faster or better than the Watershed Transform method. of the results or conclusions brief. There are no citations, tables or figures in abstract.

Estimation of shallow subsurface structures on granitic hillslopes based on electrical resistivity distribution

Electrical resistivity (ER) survey is an efficient method for investigating subsurface structure without destruction. However, this has not been used for estimating shallow subsurface zones of hillslopes that is related to the occurrence of shallow landslides. If the ER survey can alter conventional methods such as cone penetration test and boring to investigate soil thickness, an effective method for detecting landslide-prone area would be developed. In this study, ER survey was conducted on two granite hillslopes in Japan with low soil-moisture conditions to verify the usefulness of the ER survey to estimate the shallow subsurface structures. To compare the subsurface structure and the ER distribution, sounding by using a boring stick and a cone penetrometer were conducted along each ER survey line. Two soil pits were also referred near the survey lines. The subsurface structures were composed of topsoil, saprolite, and bedrock in our study sites. Results of ER survey with the unit electrode spacing of 0.5 m demonstrated that the ER increases with depth at the depths of the bottom of the topsoil layers, but the ER values were unconstrained. Below the bedrock surface, the ER generally decreased with depth, showing low ER less than 12800 Ω·m excepting an exposed bedrock indicating more than 20000 Ω·m. These spatial changes in ER are consistent with changes in grain size distribution and electrical conductivity of soil of each subsurface layer measured in this study and literature on ER of granite. ER distribution can visualize shallow subsurface structures and potential sliding surfaces for shallow landslides because the bottom of topsoil layer that was successfully estimated exhibits a discontinuity of shear strength, which generally corresponds to sliding surfaces for shallow landslides. Therefore, ER survey is applicable as an alternative to conventional methods for estimating shallow subsurface structures on granite hillslopes. Furthermore, ER survey can be a useful tool to estimate where shallow landslides will occur and how we should assess the risks of landslide hazards if a targeted subsurface zone has a distinct contrast in physical properties between each layer.

A Practical Soil Classification Method (Pscm) Based on Grain Size Distribution and Consistency of Soils for Geotechnical Applications

A Practical Soil Classification Method (Pscm) Based on Grain Size Distribution and Consistency of Soils for Geotechnical Applications

Assessment of Some Geotechnical Properties for Soils of Euphrates River Banks (Kufa- Mishkhab), Middle of Iraq

Twelve stations in the cities of Kufa and Mishkhab were selected for studying the geotechnical, including physical, engineering, chemical and mineralogical, properties of soils in the river banks along the Euphrates River. Grain size distribution of the bank soils showed higher silt than clay and sand percentages. Soil samples from the 12 stations were classified according to the USCS standards. Silt with low plasticity constituted 91% of the silt fraction, whereas that with high plasticity composed 9%. The saturated density values ranged between 1.75-2.073 g/cm3 with an average of 1.953 g/cm3, while the dry density values ranged between 1.307-1.740 g/cm3 with an average of 1.553 g/cm3. The values of the dry and saturated density are within the permissible limits. Direct shear test showed cohesion values (C) that ranged between 15-55 kN/m2 with an average value of 34.8 kN/m2. The values of the internal friction angle (Ø°) of the clay type of soil with low plasticity ranged between 8.5°-17° with an average of 9.91°. The Ø° values of the other soil types ranged between 9°-17° with an average of 25°. Therefore, clay with high plasticity had higher Ø° values than the permissible limits. The results of unconfined compression test showed a range of 22.802-58.587 kN/m2 with an average of 38.173 kN/m2, with water percentage of 30%. The mineralogical tests of the bank soil performed using XRD analysis showed that the analyzed soil samples are composed mainly of quartz, calcite, chlorite, palygorskite, and montmorillonites. The pH value ranged between 6.4-7.55 with an average of 7.10, indicating low basicity. Gypsum concentrations ranged between 0.049-12.75 % with an average of 3.99 %, while that for carbonate ranged between 5-45 % with an average of 26.16%. Sulphates concentration ranged between 0.23-5.93 % with an average of 1.85%. Several treatment measures are proposed to stabilize the soil of the studied area.

Estimation of the soil-water characteristic curve from the grain size distribution of coarse-grained soils

Coarse-grained soil, such as aggregate and coarse sand, is commonly selected to construct a capillary barrier system (CBS). The barrier effect in the CBS is mainly dependent on the hydraulic properties of the coarse-grained soils. It is noted that direct methods (such as experimental measurement) for the determination of the hydraulic properties (including the soil-water characteristic curve (SWCC) and coefficient of permeability) of soil are time-consuming and costly. As a result, indirect methods for the determination of the SWCC and permeability function of soil are commonly adopted by researchers and engineers. In this paper, a new method is proposed for the estimation of the SWCC from the grain-size distribution (GSD) of coarse-grained soils. The proposed method is based on the assumptions that the soil does not experience any volume change and the hysteresis of the SWCC is ignored. A contact angle larger than zero is adopted in this study. The results computed from the proposed model agree well with the experimental data from published studies.

Influence of Physicochemical Factors on Radionuclide Leaching from Soil

The degree of radionuclide leaching from soil in the region of the Atomic Lake (Kazakhstan) was determined. The 3H and 90Sr concentrations in aqueous extracts increase with increasing time of interaction of the soil with the leaching solution. A decrease in the 239+240Pu transfer into the solution with time may be due to the formation of colloids in the course of leaching, followed by their deposition or sorption onto soil components. Despite relatively high initial content of γ-emitting radionuclides (137Cs, 241Am, 152,154Eu, 60Co) on the level from n × 102 to n × 104 Bq kg−1 in the soil, in leaching experiments the content of these radionuclides in aqueous extracts was below the detection limit of the procedure used (<1 Bq L−1). The influence exerted on the leaching by the grain-size distribution of soil, pH of the medium, degree of mineralization, and chemical composition of water was determined. The tests performed suggest that the transfer of artificial radionuclides from the soil into water by leaching is one of the main mechanisms of radioactive contamination of the Atomic Lake water.

Effect of Grain Size Distribution of Sandy Soil on Shearing Behaviors at Soil–Structure Interface

For geotechnical construction and maintenance, assessing the shearing behavior at the soil–structure interface is significant. This study presents an experimental investigation into the effect of the grain size distribution of a sandy soil on the shearing behaviors at the soil–structure interface, using a modified direct shear apparatus. Five soil samples with different coefficients of uniformity were prepared. The normalized roughness of the structure surface (the ratio between the maximum roughness of the structure plate and the mean grain size of the soil); relative density; and maximum, mean, and minimum grain sizes of all samples were controlled in the same way. During the tests, the shear force, shear displacement, and vertical displacement were monitored. The results show that at a given shear displacement and normal stress, the sample with lower coefficient of uniformity Cu presented higher shear stress and more pronounced dilative behavior. The increase of Cu led to a decrease of the friction angle for the soil–structure interface (at both peak and ultimate states) and a decrease of the maximum vertical deformation of the soil sample during the shearing process. As Cu increased, the main force chain at the soil–structure interface turned from contact between the coarser grains to that mainly formed by the finer grains, resulting in a decrease of the shearing resistance. In comparison with the previous relevant studies, the decreasing trend of the friction angle with the increase of Cu is strongly supported.

Internal Stability Evaluation of Soils

Suffusion constitutes a major threat to the foundation of a dam, and the likelihood of suffusion is always determined by the internal stability of soils. It has been verified that internal stability is closely related to the grain size distribution (GSD) of soils. In this study, a numerical model is developed to simulate the suffusion process. The model takes the combined effects of GSD and porosity (n) into account, as well as Wilcock and Crowe’s theory, which is also adopted to quantify the inception and transport of soils. This proposed model is validated with the experimental data and shows satisfactory performance in simulating the process of suffusion. By analyzing the simulation results of the model, the mechanism is disclosed on how soils with specific GSD behaving internally unstable. Moreover, the internal stability of soils can be evaluated through the model. Results show that it is able to distinguish the internal stability of 30 runs out of 36, indicating a 83.33% of accuracy, which is higher than the traditional GSD-based approaches.

Mechanical behaviour of a compacted well-graded granular material with and without cement

Cement additions improve the performance of granular soils. However, most literature examples of cement additions are in poorly graded sands, either to mimic the behaviour of sandstones or to accentuate the mechanical differences between cemented and uncemented soils. In this article, the behaviour of a well graded granular soil, used for base and sub-base of roads, was studied by doing triaxial tests on cemented and uncemented samples. Samples were compacted to achieve a dense fabric and tested at stresses commonly used in practice. Sieving was used to understand if breakage is important and to determine the grain size distributions of the samples after compaction and shearing. The results show that the addition of small percentages of cement greatly increase stiffness and dilation. Thereby, generating larger strengths; this is particularly important at low confining stresses in roads and parking areas, where this material is commonly used. At large strains, the results show that different Critical State Lines exist for both the uncemented and cemented soils. Each line has a different slope, which is believed to be the result of the evolution of the grain size distribution of the cemented soil. The normalised data indicate that a unique state boundary surface can be determined for all three tested soils.

Modyfikacja składu granulometrycznego i właściwości geotechnicznych gruntu niespoistego za pomocą dodatku pyłu

Istotną, z praktycznego punktu widzenia, właściwością gruntów stosowanych jako materiał nasypowy lub zasypowy w budownictwie ziemnym jest zagęszczalność. Wskaźnik uziarnienia wykorzystywanych w tym celu piasków, pospółek lub żwirów charakteryzuje się stosunkowo niewielką wartością, zazwyczaj wahającą się w granicach 2,5–4,0, co pozwala na określenie ich jako trudno lub średnio zagęszczalnych. W pracy przedstawiono wyniki badań, jakie przeprowadzono w celu określenia wpływu modyfi kacji składu granulometrycznego gruntu niespoistego – piasku średniego, za pomocą dodatku pyłu lessowego na zagęszczenie. Za grunt mało spoisty przyjęto pył lessowy pochodzący z terenu Lublina. Grunty te zajmują znaczną powierzchnię obszaru miasta, a ich częste występowanie w strefi e przypowierzchniowej, czyni je łatwo dostępnymi. Badania wykonano na próbie piasku średniego o uziarnieniu naturalnym, która stanowiła próbę kontrolną oraz dwóch mieszaninach piasku średniego z pyłem lessowym, sporządzonych w stosunku objętościowym 1:1 i 2:1. Każdy z gruntów poddano analizie sitowej i areometrycznej. Uzyskano krzywe uziarnienia, a także określono procentową zawartość poszczególnych frakcji. Analiza wyników składu granulometrycznego pozwoliła na wyznaczenie wskaźnika różnoziarnistości, który dla piasku średniego wynosił 1,71 zaś dla mieszanin piasku z pyłem lessowym wzrósł do 21,8 (w przypadku próbki materiałów zmieszanych w stosunku 1:1) oraz 13,3 (dla próbki materiałów zmieszanych w stosunku 2:1). Uzyskane wyniki sugerują, iż modyfi kacja piasku średniego pyłem lessowym pozwala na zmianę klasyfikacji wytworzonej mieszaniny z gruntu trudno zagęszczalnego na dobrze zagęszczalny, a zatem możliwe jest uzyskanie większego zagęszczenia. W celu potwierdzenia tej tezy wykonano badania zagęszczenia i wilgotności optymalnej w aparacie Proctora wg metody I, dla każdego z trzech badanych gruntów. W przypadku próby kontrolnej maksymalna uzyskana gęstość objętościowa szkieletu gruntowego wynosiła 1,751 g/cm3 przy wilgotności 11,96%. Próbki piasku łączonego z pyłem lessowym w stosunku objętościowym 1:1 oraz 2:1 wykazałymaksymalne gęstości objętościowe odpowiednio 2,076 i 2,079 g/cm3 przy wilgotności około 7%. W czasie badania stwierdzono plastyczność gruntu uzyskanego przez połączenie piasku i pyłu lessowego w stosunku objętościowym 1:1 przy wilgotności powyżej 14,25%, co wynika z faktu, iż piasek o takiej zawartości pyłu stanowi grunt na granicy gruntów spoistych i niespoistych. Zwiększona plastyczność uniemożliwia zagęszczenie badanego gruntu przy wilgotności powyżej 14,5% ze względu na powstające odkształcenia oraz wykazywaną spójność. Na podstawie przeprowadzonych badań stwierdzono, iż modyfi kacja uziarnienia piasku średniego pyłem lessowym w proporcji 2:1 pozwala na uzyskanie największego zagęszczenia w badanych warunkach. Wyniki badania sugerują, iż dzięki połączeniu piasku ze stosunkowo łatwo dostępnym pyłem lessowym można osiągnąć wymierne korzyści w postaci lepszego zagęszczenia gruntu, co pozwala na jego zastosowanie w budownictwie ziemnym jako grunt nasypowy lub zasypowy oraz na wykorzystanie gruntu rodzimego na terenach lessowych.

The role of debris flow on total denudation in small basins of the Ashio Mountains, Japan

Total and continuing denudation rates were estimated using cosmogenic nuclides and intensive field observations of sediment transport in two small basins (C3 and S3) from the Ashio Mountains, Japan. The C3 basin underlain by Triassic bedded chert, while the S3 basin has evolved in altered Jurassic sandstone-shale. Continuing denudation rates were estimated from the records of coarse sediment transport and stream discharge for 6 years (2004–2009), soil grain-size distribution, and dissolved load in stream water. A debris flow was observed and the volume was measured in C3 (chert). Concentrations of cosmogenic 10Be and 26Al in fluvial sand were measured to determine spatially-averaged total denudation rates for these basins on the basis of steady-state assumption. Continuing denudation rate for C3 (chert) basin excluding the debris-flow mass accounted for ~75% of the total denudation rate as measured from the cosmogenic nuclides. Assuming a difference between the total and continuing denudation rates indicates the impact of repeat debris flows, the debris flows with the observed magnitude (the mass of 24 t) occur with the recurrence intervals of 100–550 years (mean 167 years) for C3 (chert) basin. For S3 (sandstone) basin, the continuous denudation rates were significantly smaller than the total rates, where debris flow had not occurred for at least 17 years. The large gap in the denudation rates with different time scales shows contribution of higher magnitude debris-flow events with longer recurrence intervals.

Effect of particle size distribution of cohesionless soils on the ultimate carrying capacity of open ended pipe piles under different saturation conditions

This research is performed to study the effect of grain size distribution of cohesionless soils (i.e., fine, medium, and coarse sand) on the ultimate carrying capacity of open-ended pipe pile models of different diameters under different saturation conditions (i.e., fully and partially saturated). Poorly graded clean sand of rounded particles was used as natural soil in the present study. The soil is sieved on standard sieves to obtain fine-, medium-, and coarse-graded soil according to (ASTM D 422-02). Experimental model tests were performed on four open-ended steel pipe piles models with diameters of (25, 30, 35, and 40 mm) embedded within different grain size distribution of sand prepared under fully and partially saturated conditions with specified relative density of 65%. The unsaturated states was achieved by lowering of water table according to matric suction values of soil. The relationship between matric suction and depth of ground water table was measured in suction profile set by using three Tensiometers. The soil water characteristic curve (SWCC) was estimated by applying fitting methods through the program (SoilVision). The results show that the ultimate load carrying capacity of pipe pile under unsaturated conditions is higher than those of saturated condition and increases with increasing of matric suction values. On the other hand, the fine sand shows an increase in ultimate load carrying capacity more than the other grain size distributions under unsaturated conditions for all different types of pipe pile diameters. However, the coarse sand gives a lower resistance at different saturation conditions.