Influence of Elevation on Slake Durability Index of Quartz Mica Schist: A Case Study of East Slope of Manjiazhai Open Pit

In order to study the influence of elevation on the slake durability index of the quartz mica schist, the quartz mica schist with different elevations on the east slope of the Manjiazhai open-pit mine is taken as the research object, and based on laboratory tests and statistical analysis, the variation of negative correlation between the slake durability index and elevation is obtained. The disintegration mechanism of quartz mica schist at different elevations is also discussed. The test results show that the disintegration characteristics of quartz mica schist at different elevations are related to its mineral composition, fissure channel size, and rock damage effect. As the slope height increases, the ratio of mica to quartz in the rock increases, and the greater the porosity of the rock, the more fissures in the rock, the greater the permeability coefficient, and the more obvious the change of effective stress of rock under osmotic pressure. At the same time, the higher the slope elevation of open-pit mine, the longer the weathering time of rock, the higher the cumulative damage of rock, and the lower the rock slake durability index. This study provides a new idea for guiding the research on the disintegration characteristics of similar soft rock slopes in the elevation direction.

Comparative Study on Degradability Characteristics of Evaporitic and Carbonate Rocks from Al Ain, United Arab Emirates

The slake durability index (SDI) test is a well know and extensively used to measure the degradability behaviour of rocks especially for weak rocks like mudstone, shale, evaporites, carbonates, etc. The degradability of rocks plays a critical role in engineering design process either on or in the rock mass for safe and sustainable structures. Evaporitic and carbonate rocks are vulnerable to physical, chemical and mechanical weathering, break down, as result of wetting-drying processes during the SDI test. Evaporites and carbonates are outcropped at the surface and subsurface of the Al Ain city, which is located on the south-eastern of Abu Dhabi, capital city of the United Arab Emirates (UAE) at various level, and it is one of the rapid growing cities in the UAE. However, the detailed comparative data on the slaking behaviour of evaporites and carbonates are not available presently in the study area. Therefore, this paper provides a comparative study on the degradability characteristics of evaporitic and carbonate rocks in the city of Al Ain as well as comprehensive data for the study area. 142 rock blocks (∼ 40×40×40 cm3 in size), which represent evaporitic (48 blocks) and carbonate (94 blocks) rocks were collected from various accessible either surfaces outcrops or excavated areas from the study area. 48 and 94 slake durability test samples of evaporites and carbonates were prepared and slake durability tests were performed according to the American Society for Testing and Materials (ASTM) standards. Furthermore, their compositional and textural characteristics were examined using polarized-light microscope, X-ray diffractometry (XRD), X-ray fluorescence (XRF) and scanning electron microscope (SEM). The degradability data for evaporite and carbonate rocks designate medium to very low and extremely high to very high values based on the classification after multiple cycling, Id1 to Id4, processes, respectively. The weight loss values from the first to the fourth cycles (Id1–Id4) of evaporite and carbonate samples are approximately 24–95 and 0.68-4.22 wt%. Obviously, evaporites are highly vulnerable compare to carbonates because of their differences in chemical and mineralogical structures and their reactions to the slaking fluid of distilled water. Hydration-dehydration effects on the evaporitic rocks may occur within short time compare to the carbonate rocks due to their natural occurrences. Thus, this study provide comparable and details information for the degradability characteristics of evaporitic and carbonate rocks, and likely improve the understanding of the durability of both rock types in the study area and elsewhere. Especially, such a reliable and inclusive information will compromise a practical guideline for engineers and decision makers to overcome difficulties on durability problems associated with evaporites and carbonates in the study area and elsewhere.

Compositional Features and Swelling Potential of Two Weak Rock Types Affecting Their Slake Durability

Weak and weathered rocks are well known for their sensitivity to changes in moisture content. Degrading behavior is common in weak rocks with moisture-sensitive mineral components and present numerous stability problems. The slake durability is a measure of the resistance to weakening and disintegration of rock materials which quantitatively distinguishes durable from non-durable rock materials. Several rock material parameters interact on the process of disintegration when exposed to cyclic moisture changes, whereby the content of clay is believed to play a major role. This manuscript evaluates the overall material composition of flysch and serpentinite rocks cored from the wall of the shotcrete-lined headrace tunnel of a hydropower project, including minerals, structure, porosity, the presence of micro-discontinuities, and swelling potential, and links these properties to the slake durability. Further, the different methods used to assess compositional features affecting the durability of weak rocks are evaluated and discussed. The manuscript argues that the mineralogical composition and microstructures present in the intact rock and the content of moisture-sensitive constituents, as swelling clays, control the long-term durability of weak rock material. It is demonstrated that XRD assessments are not sufficient to detect the content of brucite and swelling components, and that methods as thin section and SEM analyses should be carried out in the assessment of weak and weathered rock mass.

Research and Application of Evaluation Methods for Functional Characteristics of Oil-Based Drilling Fluid in Shale Gas Wells

Intelligent unconventional reservoir optimal production control technology is a comprehensive technology, involving geology, reservoir simulation, and efficient drilling and completion. Efficient drilling and completion provides a flow channel for unconventional oil and gas exploitation and a wellbore with good integrity for reservoir transformation, which is an important link in the efficient development of unconventional oil and gas. The application of industry standard method to evaluate the performance of oil-based drilling fluid has the problem of poor correlation. It cannot reflect the difference of performance among oil-based drilling fluid systems, which lacks the significance for field construction. Based on shale expansion, rolling dispersion experiment, and microporous membrane filtration loss test, the physicochemical mechanism of borehole wall instability in shale formation was investigated. The evaluation methods of shale lubrication, antiaccretion test, slake durability, buck hardness test, etc. are put forward, and the formula of oil-based drilling fluid is optimized. The lubrication and antiaccretion experiment method can effectively and intuitively characterize the cleaning and lubrication effect of drilling fluid on drilling tools. The slake durability evaluation method simulates the collision between drill cuttings and the drill string and well wall. The bucking hardness experiment is through testing the cuttings and the hardness change after drilling fluid action reflects its inhibitory effect. The new methods were used to evaluate the oil-based drilling fluid used in 4 wells in the Changning block. It was found that the drilling fluid of CN209H2 well adhered to the steel column with at least 0.41 g of cuttings; the recovery rate of the drilling fluid resistance of CN209H1 was up to 87.70%, and YX1200 oil-based drilling fluid plugging agent was selected through the microporous membrane experiment. In the process of drilling the well CN209H5, the new oil-based drilling fluid formulation improved the lubrication performance by 44%, accompanied by 95.48% recovery rate and less than 10 mL HTHP fluid loss at the same time. The research results show that the oil-based drilling fluid system optimized according to the new method can significantly inhibit shale hydration and dispersion and can effectively solve the problem of unstable performance of traditional oil-based drilling fluids in the Changning block.

Effects of Laumontite Hydration/Dehydration on Swelling Deformation and Slake Durability of Altered Granodiorite

ABSTRACT The mineral laumontite can undergo hydration/dehydration reactions at room temperature. The hydration/dehydration produces a 3 to 6 percent volume change in the unit cell. The effects of laumontite hydration/dehydration on swelling and slake durability were investigated using altered granodiorite containing laumontite from the dam foundation of Yangfanggou Hydro Power Station, Sichuan, China. The occurrence of laumontite in altered rocks was first determined by petrological analysis. Typical samples were then collected for laboratory X-ray diffraction (XRD) analyses, free swelling tests, and slake durability index (SDI) tests. The test results were analyzed to determine the quantitative relationships between laumontite content, maximum axial strain, and slake durability index. We found that hydration of laumontite led to rock swelling. As laumontite content increased, maximum axial strain increased linearly; if water penetrated the rock quickly, swelling occurred over a short period. The hydration/dehydration of laumontite decreased slake durability of the rock; the SDI decreased approximately linearly as laumontite content increased.

Slake Durability Index of the Stone Aggregate Used in the Morelia Michoacán Region

The study of durability is very important because buildings are expected to last; since durability is attributed to the materials used in construction, the study of such materials is required. Among them, stones play a fundamental role as part of the structures, as well as stone aggregates in the elaboration of asphalt blends and concrete blends. Bearing this facts in mind, quarry stones of volcanic and crushed materials were studied in the mexican state of Michoacán.In this work, the Id2, density, and absorption data were correlated to obtain a mathematical model that helps predict Id2 and verify the relationship between the variables. On the other hand, logistic regression was used to classify rock quarries according to their durability index.