Sustainable Utilization of Powdered Glass to Improve the Mechanical Behavior of Fat Clay

Hassan Mujtaba,Usama Khalid,Khalid Farooq,Mehboob Elahi,Ziaur Rehman,Hussain Mustafa Shahzad 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.12

Civil engineering infrastructure like roads, bridges, railway tracks, and building structures constructed on fat clay becomes suspicious due to adverse change in the behavior of such soil on interaction with water. To solve such problems especially in underdeveloped countries, application of industrial waste like glass is associated with technical, financial, and environmentalbenefits. Emphasis of current study is to determine the consequences of powdered glass (GC) on mechanical behavior of fat clay. A fat clayey sample was collected from location of Nandipur, and glass was taken from local glass market in powdered form. Samples were remolded at optimum moisture content and maximum dry unit weight by mixing GC up to 14%. Soil classification tests, modified compaction tests, unconfined compression tests, one-dimensional consolidation tests, California bearing ratio (CBR) tests, and scanning electron microscope were performed. With increasing GC, the consistency limits, compression characteristics, swell characteristics, and optimum moisture content decreased while maximum dry unit weight, yield stress, CBR, and unconfined compression strength increased. Influence of GC is also observed on microstructure of treated clay. After 12% GC, aforementioned geotechnical characteristics behave inversely for selected clay. The optimum GC-value for the tested clay is about 12%, however, this value may vary from clay to clay.

Evaluation of Relative Density and Friction Angle Based on SPT-N Values

Hassan Mujtaba,Khalid Farooq,Nagaratnam Sivakugan,Braja M. Das 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.2

This study is an attempt to evaluate relative density and friction angle of sands on the basis of SPT-N values. In order to develop the relationships among relative density (Dr), friction angle (φ ) and SPT-N value, field and laboratory test results from sixty boreholes executed in sandy deposit were used. The field tests include the SPTs conducted in the boreholes and the determination of in-situ density at various depths in the boreholes using the pitcher sampler whereas the laboratory tests include routine classification, direct shear box, maximum and minimum density and specific gravity tests. The SPT-N values were observed to vary between 4 and 100 and the in-situ bulk density of undisturbed samples as recovered through pitcher sampler are in the range of 13.24 ~ 18.44 kN/m3. The soil samples are classified as poorly graded sand (SP), poorly graded sand with silt (SP-SM) and silty sand (SM) on the basis of Unified Soil Classification System. The values of minimum dry unit weight fall in the range of 12.22~14.95 kN/m3 and maximum dry unit weight varies in the range of 14.64~19.17 kN/m3 as obtained through vibratory table. Based on the test results, correlation analysis was performed to identify the parameters that affect relative density. The parameters include SPT-N value corrected for field procedures (N60), relative density (Dr), void ratio range ( ), effective overburden stresses and in-situ dry density (γdf). Based on the results of correlation analyses, it was observed that SPT-N values alone cannot be related to Dr. Therefore, multiple regression analysis was carried out using Statistical Package for the Social Sciences (SPSS) software and relation between relative density, corrected SPT-N value and effective overburden stress is being proposed. The variation between experimental and predicted values falls within ± 10% at 95% confidence interval. Validation of the proposed correlation was also performed by using an independent data set which indicated that the prediction by using the proposed correlation also falls within ± 10%. Further, comparison of the proposed correlation with other similar relationships already available in the literature was also performed. In addition to the above, correlation between φ and SPT-N60 has also been proposed. It has been observed that the experimental and predicted values of friction angle fall within ± 10% with 95% confidence interval. The proposed correlations may be very useful in the field of geotechnical engineering during feasibility/preliminary design stage for rapid estimation of relative density or friction angle based on the field SPT-N60 values.

Nonstandard Backstepping Based Integral Sliding Mode Control of Hydraulically Actuated Active Suspension System

Flayyih Mujtaba A. Flayyih,Hamzah Mohsin N. Hamzah,Hassan Jafar M. Hassan 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.6

In this paper, the integral sliding mode control (ISMC) with non-standard backstepping is utilized for designing an automotive active suspension system hydraulic actuator. The main objective of this design is to make the suspension system’s ride more comfortable while keeping the road holding and rattling space within safe bounded limits. The controller design consists of applying the ISMC to perform a virtual control force, that meets all suspension requirements, besides utilizing a hydraulic model by a non-standard backstepping control algorithm taking into consideration the uncertainty and nonlinearity of the hydraulic system. The main advantage of ISMC is to have a robust controller, such that the stability of the system appears from starting its states at the switching surface where system nonlinearity, parameter changes, and road disturbances are rejected by a discontinuous control term present strongly in the suspension dynamics. This work demonstrates the effectiveness of the present controller design through the simulation of a 2-DOF quarter car system equipped with a passive suspension. The results vividly showcase how the current design enhances the overall performance of the system.

Optimization of Sand-Bentonite Mixture for the Stable Engineered Barriers using Desirability Optimization Methodology: A Macro-Micro-Evaluation

Khalid Farooq,Zia ur Rehman,Muqadas Shahzadi,Hassan Mujtaba,Usama Khalid 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1

In this paper, Desirability Optimization Methodology (DOM) is employed to achieve optimum sand bentonite mixture (SBM) based on multiple antagonist macro-geotechnical responses of the compacted SBM prepared using poorly graded sand with the mean grain size around 0.2 mm and bentonite with plasticity index around 157% for the stable engineered barriers (EBs). For this purpose, varying mix designs of SBM compacted at compaction energy of 2,700 kN-m/m3 are initially tested to determine their mechanical properties, volumetric-change behavior, and hydraulic conductivity. The unconfined compressive strength, cohesion, angle of internal fiction, swell pressure, compression index, and hydraulic conductivity are taken as the geotechnical design parameters for the SBM. Mathematical models are developed and statistically validated for these design parameters using sand content (SC) and bentonite content (BC) as the predictors. In addition, models are also developed to predict compression curves for compacted SBMs. Moreover, microstructural evaluation is conducted through scanning electron microscope (SEM) analysis to determine the SBM having a desirable microstructure for stable EB. It is observed that a major shift in the microstructure from medium pores to micro-pores occurs for the BC between 20% and 30%. Afterward, optimization of SBM is carried out by integrating developed models for the geotechnical design parameters in a desirability function (D) algorithm, which is subsequently simulated by setting maximization of strength and minimization of swell pressure, compressibility and hydraulic conductivity of compacted SBM as the goals. A reasonably high D-value is achieved for the SBMs having SC:BC in a range of 74:26 to 78:22 with the highest at 75.63:24.37 against the set goals. This study manifests an effective and pragmatic strategy for designing the SBM for a stable EB considering its antagonist hydraulic, volumetric change, and mechanical responses.