Zainab Mohamed

Long-Wavelength Elastic Wave Propagation Across Naturally Fractured Rock Masses

Geophysical site investigation techniques based on elastic waves have been widely used to characterize rock masses. However, characterizing jointed rock masses by using such techniques remains challenging because of a lack of knowledge about elastic wave propagation in multi-jointed rock masses. In this paper, the roughness of naturally fractured rock joint surfaces is estimated by using a three-dimensional (3D) image-processing technique. The classification of the joint roughness coefficient (JRC) is enhanced by introducing the scan line technique. The peak-to-valley height is selected as a key indicator for JRC classification. Long-wavelength P-wave and torsional S-wave propagation across rock masses containing naturally fractured joints are simulated through the quasi-static resonant column (QSRC) test. In general, as the JRC increases, the S-wave velocity increases within the range of stress levels considered in this paper, whereas the P-wave velocity and the damping ratio of the shear wave decrease. In particular, the two-dimensional joint specimen underestimates the S-wave velocity while overestimating the P-wave velocity. This suggests that 3D joint surfaces should be implicated to obtain the reliable elastic wave velocity in jointed rock masses. The contact characteristic and degree of roughness and waviness of the joint surface are identified as a factor influencing P-wave and S-wave propagation in multi-jointed rock masses. The results indicate a need for a better understanding of the sensitivity of contact area alterations to the elastic wave velocity induced by changes in normal stress. This paper’s framework can be a reference for future research on elastic wave propagation in naturally multi-jointed rock masses.

Empirical Correlation of P-wave Velocity to the Density of Weathered Granite

Tropical rock weathering caused decomposition and disintegration of granite rock minerals thus reduces it physical and mechanical properties. The conventional method of characterization and classification of weathered granite becomes a discouraging task due to low sample recovery. A shift to non-destructive technique for characterization of weathered granite by using elastic wave velocity was studied. The deterioration of the quality of weathered granite was defined in term of density as tangible variable. An experimental testing to determine the elastic wave velocity by Free–Free Resonant Column (FFRC) test was introduced and carried out on weathered granite of Grade II, Grade III and Grade IV. The results were compared to the common PUNDIT technique for reliability test. The degree of accuracy of elastic wave velocity by the two test methods showed a good consistency. From the experimental study, an empirical correlation between elastic wave velocity to the density of tropically weathered granite is proposed.

Landslide Mapping Using LiDAR in the Kundasang Area: A Review

Kundasang has been identified as one of the major geological hazardous area in Malaysia. This is due to the existence of numerous landslides occurrences at some locations in the Kundasang area. The occurrence of landslide has resulted substantial damaged to the building structure, access road, telecommunication towers and agriculture orchards. Several studies and attempts of landslide investigation have been conducted in the Kundasang area using various methods such as localized drilling method, geodynamic mapping and a regional geological structure mapping. These methods have not gathered sufficient information which is considered important in developing a complete landslide inventory to assess landslide susceptibility due to constraint of time and cost. This paper presents a critical review to determine the potential use of light detection and ranging (LiDAR), specifically airborne laser scanning (ALS) for landslides mapping to assess landslide susceptibility of the Kundasang area. Several researchers found that the usage of light detection and ranging (LiDAR) such as airborne laser scanning (ALS) has been a successful technique in landslides mapping. Availability of this new technology for identification and mapping of landslides will assist in obtaining of landslide inventory in term of providing clear, complete and accurate information to investigator for the process of interpretation. With such comprehensive information, landslide susceptibility assessment can be conducted precisely. Most likely the usage of ALS may be a way forward for investigating the landslide phenomena in Malaysia.

The Influence of Cyclic Load to the Properties of Weathered Granite

This paper briefly elaborates the influences of cyclic loading to the physical and dynamic properties of weathered granite. Petrological description of weathered rocks is also discusses as well as other important characteristics of rock which may affect the cyclic loads analysis. To find out the possible effect between weathered rock physical and dynamic properties with cyclic loading, weathered specimens are tested under same cyclical load condition of 1 Hz, stress ratio of 0.14 and using sinusoidal waveforms.

The Effect of Cyclic Stress on the Strain and Microstructure of Weathered Granite

This paper elaborates the effect of cyclic stress on tropically weathered granite of grade II, grade III, and grade IV. The specimens were tested under cyclic loading with frequency of 1 Hz, under constant sinusoidal waveform and identical stress ratio of 0.17. The test was setup under maximum stress of 70, 80, and 90 % of its ultimate strength. The compressional wave velocity, shear wave velocity, and uniaxial compressive strength were recorded before and after cyclic load testing in order to observe the post-cyclic effect on rock properties. Petrographic analysis using SEM and thin-section images were also captured to investigate the change in rock microstructure under cyclic load. Result reveals that when specimen is loaded at 70 and 80 % of its ultimate strength, eight out of nine specimens are able to withstand the one million cycles. However, at 90 % of the ultimate strength, only two out of nine specimens were failed before reaching one million cycles. SEM images were evidently showing the presence of abundance microcracks due to cyclic load.

Electrokinetic Remediation to Remove Heavy Metal from Contaminated Soils Using Purging Solution

This study was designed to determine the physical characteristic of soil from mining area, the level of heavy metal contamination on site, and performance of pH and concentration of heavy metal after electrokinetic. For each type of purging solution and soil sample, six days of treatment time were performed with low direct current of 1.076 V to each purging solution. Soil sample consists of sand and gravel. Changes on level of pH and concentration showed the movement of metal ions and electrons from anode to cathode. The removal efficiency for acetic acid is much higher with 78 % compare to deionized water of 53 %. The existing level of contaminant was also determined by using single factor index. This provides a better view on the existing level of metal contaminant at site.

The correlation between internal erosion resistances with the hydraulic conductivity of residual soil

Soil physical properties, internal erosion resistance and hydraulic conductivity characteristics of a residual soil are presented in this paper. Hydraulic conductivity of underground soil can influence mechanism of internal erosion resistance and thus contribute to landslides. A randomly eight (8) selected soil samples were extracted from soil slopes within UiTM, Shah Alam Campus in which the samples are different in nature. Compaction test has been applied to all the samples in order to measure the value of Optimum Moisture Content (OMC) and maximum dry density, which will give a fair result in comparison of all disturb (remoulded) samples used in determining the hydraulic conductivity by using Falling Head test. It is found that the coefficient of permeability is influenced by the classification of soil, maximum dry density and OMC of soil. A pinhole test, crumb test and cylinder dispersion test were conducted to investigate the soil dispersibility characteristic. The results shows that the soil dispersibility characteristics are clearly determined and it shows in good agreement with the hydraulic conductivity of the compacted soil. This indicates that the soil samples with higher composition of coarse-grained particles have higher dispersibility and hydraulic conductivity that lead to lower resistance to internal erosion.