Aly Ahmed

Assessment of 3D Slope Stability Analysis Methods Based on 3D Simplified Janbu and Hovland Methods

AbstractAn assessment of three-dimensional slope stability analysis methods in terms of safety factors using several idealized sliding masses composed of plane sliding surfaces was made. Three-dimensional safety factors were calculated and compared for different study cases considered in this study on the basis of the exact solution methods, the Hovland method, and the 3D simplified Janbu method. Parameters investigated in this study included the effect of water pressure, horizontal seismic force, the changing gradient of a sliding surface, the changing lateral gradient of a sliding surface, and anchor force. Results showed that the Hovland method gives smaller safety factor values compared to the exact solutions, especially in cases of narrow failure width and high water pressure along sliding surfaces whereas the 3D simplified Janbu method gives the same safety factor values as the exact solutions

Application of Gypsum Waste Plasterboard and Waste Plastic Trays to Enhance the Performance of Sandy Soil

This paper presents the results of a research project that evaluated the use of recycled gypsum obtained from waste plasterboard along with strips of waste plastic trays to enhance the performance of tested soil. Recycled gypsum was used as a stabilizing agent for stabilized soil to improve the compressive strength, whereas the waste plastic trays were used to improve the tensile strength. The effects of waste gypsum content, size, aspect ratio and waste plastic trays content were investigated to determine the mechanical behavior of soil treated with such waste materials. Experimental test results showed that unconfined compressive and splitting tensile strengths increased with increasing waste gypsum content. The increase in waste gypsum has a more significant effect on the unconfined compressive strength than on the tensile strength. Adding strips of waste plastic trays to samples treated with waste gypsum enhanced the splitting tensile strength. The size, aspect ratio and content of waste plastic trays have significant effect on the enhancement of soil strength.

On the compressive strength and geo-environmental properties of MC-clay soil treated with recycled bassanite

The use of recycled bassanite, produced from gypsum wastes, in ground improvement projects is initiated recently in Japan to eliminate the huge quantities of gypsum wastes. Meanwhile the use of recycled bassanite has a positive effect on the environment and economy, it has many challenges. These challenges are related to the release of fluorine more than the standard limits results in contaminated fluorine soil. This research investigates the effect of the amount of bassanite, and water content on the release of fluorine from MC-clay soil stabilized with bassanite, taking in consideration their effect on the compressive strength. Recycled bassanite was mixed with furnace cement with a ratio of 1:1 to prevent the solubility of bassanite. Different amounts of this admixture were mixed with the tested soil at different water contents. Unconfined compression test was used to determine the compressive strength while the solubility of fluorine was used to represent the geoenvironmental properties in term of the release of fluorine. Scan electron microscopic (SEM) test was done to identify the development of cementation compounds in the matrix of treated-bassanite soil. Test results showed that, the addition of bassanite had a significant effect on the improvement of compressive strength by increasing the amount of bassanite. Curing time had a significant effect on the increase of compressive strength, the strength increases with the increase of curing time, especially in the later curing time. The release of fluorine increases with increasing the amount of bassanite in soil mixture. The increase of water content had an indirect effect on the release of fluorine while it had a negative effect on the improvement of strength and consuming the amount of admixture. The increase of strength is associated with the decrease of the release of fluorine. Recycled bassanite, produced from gypsum wastes, had a potential to be used as a stabilizer material for MC-clay soil and meet the standards of environment.

Simplified Regression Model to Predict the Strength of Reinforced Sand with Waste Polystyrene Plastic Type

A proposed regression model was developed based on experimental data using regression analysis method to predict the strength of sand reinforced with strips of waste polystyrene plastic type. Three different variables were studied to investigate the behavior and strength of reinforced sandy soil with waste plastic strips. These are the content, size and aspect ratio of plastic strips. For this purpose, a series of unconfined compression and splitting tensile tests were conducted on unreinforced and reinforced sand specimens. Test results showed that using strips of waste plastic polystyrene type improved the strength of the tested soil. Increasing content of waste plastic has a more significant effect on the enhancement of splitting tensile strength compared to the enhancement of compressive strength. Content, size and aspect ratio of waste plastic strips have significant effects on the improvement of strength. Utilization of such waste plastic type, which polystyrene, in this way will help in reducing the quantity of solid waste as well as reducing the cost of ground improvement. Results showed that multiple linear regression models can accurately predict the strength of sand reinforced with waste plastic strips within the range of the studied variables in this paper. Consequently, using such regression models will save time as well as reduce laboratory costs.

Improvement Properties of Cohesion-Less Soil Using Recycled Bassanite

Solid waste management is a serious problem over the world. Therefore, reduction, re-use and recycling of waste have become major issues in recent days. Gypsum waste plasterboard is considered one example of these waste materials. This study evaluates the use of recycled bassanite, which is derived from gypsum waste plasterboard, to enhance the performance of two types of cohesion-less soil. Recycled bassanite was utilized as a stabilizing agent to improve both compressive and splitting strengths of the tested soil. The effect of bassanite content, soil type, water content and curing time were investigated to explore the behavior of treated soil with recycled bassanite. Test results showed that increase of bassanite content is associated with increase in optimal moisture content, while no significant increase in the dry unit weight was observed. Both compressive and splitting tensile strengths enhanced with the additives of recycled bassanite. The increase of bassanite content had a more significant effect on the compressive strength compared with the effect on tensile strength. The use of recycled bassanite to enhance the strength of sandy soil had a more significant effect compared with silty soil. The effect of curing time on the strength of treated samples was more significant in early curing ages compared with late curing ages. The strength decreased significantly in case of stabilized samples prepared with water content at the wet-side of the compaction curve. However, insignificant decrease in the strength of the stabilized sample was detected with moisture content at the dry-side of compaction curve. This research meets the challenges of our society to reduce the quantities of gypsum wastes, producing useful material from waste materials that will help to a sustainable society.

On the Tasikmalaya Earthquake Induced Landslide in Indonesia: Field Investigation

On Wednesday September 2nd, 2009 at 14:55 pm the 7-magnitude earthquake struck the southern coast of the main island of Java near Tasikmalaya city in Indonesia. The earthquake and subsequent landslides resulted in at least 75 deaths, more than 900 injuries, and the displacement of more than 88,000 people from nine districts in Central and West Java which are near the epicenter as of September 7. Tremors damaged or destroyed more than 55,000 houses in 13 districts, including the most-affected areas of Tasikmalaya, Cianjur, Garut, and Bandung. The magnitude of this earthquake was strong enough to cause office blocks to sway and windows to shatter in Jakarta. Many houses and commercial buildings had collapsed in the worst-hit areas around the towns of Tasikmalaya and Sukabumi. The US Geological Survey reported that the quake occurred less than 200 km south of Jakarta at a depth of 49 km. The location of this earthquake was found in latitude 7.809° south and longitude 107.259° east. Site investigations were done to explore the hazards induced by the Cikangkareng landslide. Based on site investigations, it was found that there were various disasters and rock avalanches observed in the affected area. The run-out distance of rock avalanches was found approximately 600 m measured from the toe of mount. The profile of the rock avalanche, which was induced by landslide, consists of three segments with different inclination angles.

Small-Scale Flume Test under Dynamic Condition for Rock Avalanches

The objective of this research is to study dynamic behavior and responses of rock avalanche. A series of small-scale flume tests was performed on a shaking table subjected to sine waves. Simple constrained flows were generated by releasing granular materials down a flume with two inclined portions at an assigned position. Material type and the frequency and amplitude of input sine waves were varied respectively to investigate their influences on run-out. Besides, superposition mode (simultaneous release and shake) was proposed to reflect the superposition of static and dynamic effects, comparing non-superposition mode (release first and then shake). Results show that run-out increased with decreasing frequency and increasing amplitude. The difference in run-out at various amplitudes reduced when the frequency increased. The run-out was more sensitive to frequency at large amplitude than that at small amplitude. Coarse materials went further than fine materials under dynamic condition. The increment of run-out in superposition mode was larger than that in non-superposition mode at 200 and 300 gal, and was smaller at 400 gal. The increment of run-out increased as the frequency reduced and the amplitude increased in these two modes.