Rock strength is defined as the limit of the ability of a rock to resist stress or deformation without breaking. Testing methods recommended by ISRM (International Society of Rock Mechanics) and ASTM (American Standards Testing Material) include unconfined compressive strength (UCS), point load index (PLI), indirect tensile strength (ITS), Schmidt hammer rebound (SHR), sonic velocity (V p and V s ), and slake durability index 2nd cycle (I d2 ). This contribution compares the results of these methods and explores the influence of rock composition and texture on Lower Miocene evaporites from Al Ain city, United Arab Emirates (UAE). These sedimentary rocks are common in the Arabian Peninsula as exposures or in the subsurface where they may constitute the foundations of buildings. A large number of UCS, PLI, ITS, SHR, SV, and I d2 tests were carried out on both core samples and rock blocks according to ASTM Standards. Examination of compositional and textural characteristics of representative rock samples was performed using XRD, XRF, polarized-light microscopy, and SEM. The results reveal variable correlations between the rock strength parameters with specific significant values between 0.53 and 0.72. The effect of composition and texture of the evaporitic rocks on their strength behavior is related to impurities such as clay minerals and celestite and grain interlocking textures. Despite the limited compositional variability of the evaporitic rocks (5-10%), the textural variability may present a challenging feature in rock strength testing and should be taken as a primary factor for consideration during applications.

No abstract

Rock strength is defined as the limit of the ability of a rock to resist stress or deformation without breaking. Testing methods recommended by ISRM (International Society of Rock Mechanics) and ASTM (American Standards Testing Material) include unconfined compressive strength (UCS), point load index (PLI), indirect tensile strength (ITS), Schmidt hammer rebound (SHR), sonic velocity (V p and V s ), and slake durability index 2nd cycle (I d2 ). This contribution compares the results of these methods and explores the influence of rock composition and texture on Lower Miocene evaporites from Al Ain city, United Arab Emirates (UAE). These sedimentary rocks are common in the Arabian Peninsula as exposures or in the subsurface where they may constitute the foundations of buildings. A large number of UCS, PLI, ITS, SHR, SV, and I d2 tests were carried out on both core samples and rock blocks according to ASTM Standards. Examination of compositional and textural characteristics of representative rock samples was performed using XRD, XRF, polarized-light microscopy, and SEM. The results reveal variable correlations between the rock strength parameters with specific significant values between 0.53 and 0.72. The effect of composition and texture of the evaporitic rocks on their strength behavior is related to impurities such as clay minerals and celestite and grain interlocking textures. Despite the limited compositional variability of the evaporitic rocks (5-10%), the textural variability may present a challenging feature in rock strength testing and should be taken as a primary factor for consideration during applications.

Evaporitic rock durability induced by groundwater cause several construction challenges, but representative experimental studies to evaluate such conditions are still missing. Therefore, this study intended to provide better and more realistic degradability features of evaporites with groundwater besides a comparison with distilled water as slaking fluids. Forty-eight evaporitic rock blocks were collected from Abu Dhabi area, United Arab Emirates. 96 slake durability index (SDI) tests were performed, 48 with each of the slaking fluids; groundwater and distilled water, and their textural, mineralogical, and geochemical attributes were also examined before and after the SDI tests. In comparison to mineralogical and textural modifications, slaking fluid had a greater impact on the chemical composition of evaporitic rock. The study shows that the degradability of evaporites with groundwater and distilled water indicates a wide range from very low to high. The mean weight loss values after four cycles with groundwater and distilled water vary from 11 to 77 and from 4 to 81 wt.%, respectively. Consequently, slaking with groundwater illustrates a wide range compared to the slaking with distilled water. This could be due to quick interactions between groundwater and evaporites and fast hydration-dehydration process than distilled water due to the chemical composition of the groundwater. It is recommended to investigate the attributes of evaporitic rocks as well as groundwater geochemistry for safe, cost-effective, and sustainable structures.

Thirty two bottom sediment samples were collected from four different areas from Arabian Gulf, United Arab Emirates. These areas include: (a) Dubai, (b) Sharjah, (c) Ajman, and (d) Ras Al-Khaimah. The present study focuses on the levels of copper, lead, iron, manganese nickel, cadmium, zinc and vanadium in order to assess the extent of environmental pollution and to discuss the origin of these contaminants in sediments. Positive correlations are found between increase of heavy metals concentration and decrease of grain size. It is well established that heavy metals tend to be concentrated in the finer grain sizes of bottom sediments of the studied areas. Some large size grain sediments show high heavy metals concentrations due to formation of large agglomerates from the smaller particles enriched by contaminations. The concentrations of copper, zinc, lead, iron, manganese, nickel, cadmium, and vanadium are varied between 5.05, 10.15, 2.82, 3230, 119.0, 16.92, 0.105, and 11.04 µg/g, respectively, which are within the permission levels. This means that the samples containing these metals were derived from nonpollutant sources.