The use of construction and demolition wastes (C&D) in engineering applications is an important development for better sustainability. The main objective of this study, therefore, was to increase the use of C&D by improving their engineering behaviour. For this purpose, two methods were employed in this study: first, adding the virgin aggregates (VA) to the C&D, called hybrid C&D (C&D-VA), and second, reinforcing the C&D with a geogrid material. Test samples were prepared in six groups.The first three test groups were prepared with C&D, VA and C&D-VA. The other three test groups were formed with geogrid-reinforced C&D, VA and C&D-VA. Firstly, for the strength characteristics of the samples, the unconfined compressive strength and the California bearing ratio values were obtained with large-scale experiments. Subsequently, for the resilient behaviour of the samples, the resilient modulus values were determined using a large-scale triaxial test device. Consequently, some significant improvements were achieved via the methods employed in this study. In addition, it was observed that the best reinforcement effect for the C&D occurred when the geogrid was used and the VA was added to the C&D.
Saturated, cohesionless soils can temporarily lose their shear strength due to increased pore-water pressure under the effect of repetitive dynamic loads such as earthquakes. This event is defined as soil liquefaction and causes significant damage to structures. the liquefaction potential of soils depends on many soil parameters obtained in the field and from laboratory tests. In this study new models have been developed to estimate the liquefaction potential of cohesionless soils. For this purpose, 837 soil data sets were collected to calculate the liquefaction potential with nonlinear multiple regression and artificial intelligence in the cities of Kayseri and Erzincan. the models based on Nonlinear Multiple Regression Analysis, Artificial Neural Networks, and Adaptive Neuro-Fuzzy-Inference System techniques were compared with the results of the simplified method. Determination coefficients (R2) and various error rates were calculated for the performance-evaluation criteria of the models. The proposed ANN model effectively found the complex relationship between the soil and the input parameters and predicts the liquefaction potential more accurately than other methods. It has an overall success rate of 90 percent and the lowest mean absolute error rate of 0.024. With the improvement of existing methods, new models have been introduced to estimate the liquefaction probability of soils.
This paper presents the characterization of pure bentoniteand zeolite-type clays and of various contents mixed with sand. The engineering properties of zeolites, bentonites and sand, which are commonly found in Malatya, Turkey, were evaluated in terms of their suitability for geotechnical applications. The crystallinity and structure of solid specimens of bentonite and zeolite were analysed with X-ray diffraction. Then both soils were mixed with sand in various proportions and the enhancement of the engineering properties was investigated. The properties of the mixtures, such as specific gravity, optimum water content, and dry unit weight mixtures, were initially determined. A set of direct shear tests was carried out to determine the shearstrength parameters of the specimens. As a result of extensive laboratory tests, linear correlations were observed between the water content and the consistency limits with the bentonite and zeolite contents in the sand mixtures. The highest for among each sample tested was achieved with the addition of 50 % bentonite and zeolite (i.e., BS50 and ZS50) as 44 and 38 kPa, respectively. A literature survey was carried out to reveal the test results of similar studies. In addition, using the test results from these literature studies and the current study, an NN-based prediction model was developed. Th e forecast models developed separately for cohesion and internal friction angle had high correlation coefficients: R2 equal to 0.84 for cohesion and R2 equal to 0.78 for the friction angle.
Rainwater infiltration is the crucial factor in any evaluation of rainfall-induced slope stability. The amount of rainwater infiltration is dependent on factors such as the rainfall intensity, the rainfall duration, the slope geometry, the hydraulic properties of the soil, and the initial pore-water pressure distribution. In this paper the effects of the variability in hydraulic properties of unsaturated soil on the rainwater's infiltration are investigated and discussed. Different hydraulic conductivity functions (HCFs) by considering the uncertainty in saturated volumetric water content (theta(s)) and the soil-water characteristic curve (SWCC) are proposed. The seepage analyses for five cases (incorporating the uncertainty in theta(s), SWCC, and hydraulic conductivity, k(s)) are conducted in this study. The results indicated that the effect of the variability in hydraulic properties of the unsaturated soil on the infiltration is much dependent on the initial suction in the slope soil. If the initial suction level is low (relatively wet conditions), then the variability in the hydraulic properties has an insignificant effect on the infiltration. On the contrary, if the initial suction level is high (relatively dry conditions), then the variability in the hydraulic properties has a significant effect on the infiltration.
This study analyzes the impact of weathering on the effectiveness of granite as a stabilization agent for clay soils. A sample of clay soil was obtained from Mansehra District (Hazara, Pakistan) and its composition was determined. The sample consists of quartz, feldspare, kaolinite and illite, and is categorized as a CH soil following the Unified Classification System. Samples of fresh (non-weathered) and variously altered, i.e., slightly weathered, moderately weathered and highly weathered Mansehra granite were collected. Two different amounts (12.5 % and 25 %) of these granite varieties were mixed with the clay soil sample and geotechnical properties (plasticity index, activity, cohesion, angle of internal friction, maximum dry density, optimum moisture content, unconfined compressive strength and allowable bearing capacity) of the resulting mixtures were determined following the corresponding standard ASTM procedures. The results reveal that the addition of all the granite types, except the highly weathered variety, leads to an improvement in the parameters of the soil. However, the magnitude of the positive impact produced, strongly depends on the degree of weathering of the added granite, i.e., the improvement in the soil properties decreases with the increasing degree of weathering of the added granite. This is because the weathering of granite principally involves the conversion of feldspars into clay minerals. As the weathering progresses, the abundance of clay minerals increases, while that of feldspars decreases. As a result, the water-absorption capacity of the granite increases and its specific gravity decreases. Hence, the higher the degree of granite weathering, the greater the abundance of clay minerals, the lower the specific gravity and the higher the water-absorption capacity, and thus the smaller the potential for the added granite to improve the properties of the soil.
