Alsidqi Hasan

Strength Properties of JSC-1A Lunar Regolith Simulant

The paper presents a description of physical properties and a characterization of shear strength behavior of JSC-1A lunar regolith simulant. Specific gravity of solids, particle size analysis, and minimum and maximum index densities were measured according to ASTM standards. A series of axisymmetric triaxial experiments were conducted on JSC-1A specimens at two densities and a wide range of confining pressures. The stress-strain and volume change behavior of JSC-1A is presented and discussed. The results show that the peak friction and dilatancy angles are highly influenced by specimen density and confining pressure. Two models were developed to predict the peak friction and dilatancy angle, as a function of relative density and mean effective stress at the critical state. It was found that JSC-1A closely resembles the morphology and specific gravity of solids of some of Apollo regolith samples reported in the literature. Shear strength properties are presented within the framework of Mohr-Coulomb and friction-dilatancy theories. The effect of reduced moon gravity on strength parameters is also presented and discussed.

Evaluating force distributions within virtual uncemented mine backfill using discrete element method

This paper investigates the distribution of intergranular forces within uncemented mine backfills using the discrete element method (DEM) and compares it with the existing analytical method. The virtual backfilling is modeled via the DEM to simulate the underground mining stopes backfilling with uncemented granular materials. Normal and shear forces of all particle contacts within the model backfill are tracked and analyzed with particular attention to the effect of sidewall friction. The DEM evaluates normal force chains and reveals a concentration of high forces within the model backfill. The DEM shows profiles of forces that are distinctly different from those obtained from analytical solutions. Quantitative analyses of the spatial distribution of forces, number of contact points, and changes in the orientation of forces are presented. The DEM demonstrates its capacity as a good tool for looking closely into the backfill on a particle scale. It highlights potential force distribution and concentration within a backfill and shows the limitations of analytical solutions, which helps engineers in the mining industry to better understand the possible mechanisms within backfill.

Variable penetration rate testing for shear strength of peat – a review

Abstract This paper presents a review of the advances in the variable penetration rate testing methods on inorganic soils and its potentials to investigate the appropriate penetration rate and resistance factors for penetrometer testing of peat. A partially drained condition, which often leads to misinterpretation of test results, has been observed in peat penetration testing when the standard rate of 20 mm/s is used. Although the impact of rate-effects on penetration resistance measured with CPTu, T-bar and ball penetrometer have been investigated extensively in various intermediate soils, research is limited on how penetration rate controls drainage conditions and affects consolidation behaviour in peat. This review synthesises research developments in using variable penetration rate tests. The objective is to evaluate the transition of drainage conditions and consolidation behaviour of inorganic soils while focusing on its adaptability for peat. The review provides guidance on the investigation of the penetration rate testing in peat.

Temperature change and the total stress anomaly in paste backfill

This paper presents preliminary results from a laboratory backfill model test in order to explain the effect of temperature change during the cement hydration on the total stress within cemented paste backfill. It is conducted via temperature control test in the absence of the cement. This investigation is an attempt to resolve an anomalous behavior reported in recent full scale monitoring reports, where the total vertical stress at the stope base shows a progressive increase after backfilling is terminated. The result in this paper shows that the total vertical stress is not affected by the level of the temperature but rather by the temperature gradient. The empirical relationship between the temperature gradient and the change in the total vertical stress is proposed. The total stress anomaly found in the full scale monitoring of paste backfill could be explained by the finding.

Measurement of Amorphous Peat Shear Strength in the Direct Shear Box at High Displacement Rates

The ASTM standard provides guidelines for the drained direct shear test (DST) and requires the samples to be sheared at rates estimated from time to failure,

Experimental assessment of 3D particle-to-particle interaction within sheared sand using synchrotron microtomography

t_{f} \ge 50t_{50}

Pore structure in a gold mine cemented paste backfill

tf≥50t50 (where