It is well known that mass movements and slope failures owe their existence to several attributes, most of which are either man-made or man accelerated. In every slope gravity induced shear stresses exist which increase with the slope height, slope inclination and unit weight of the slope forming materials. Shearing stresses are also added, particularly in the surface zone, because of thermal expansion and contraction, freezing-thawing action and a host of other factors. Under normal conditions, the shear stress along the slope is in equilibrium with the shear resistance of the slope. But these are often influenced and modified by external and internal factors and as soon as the shear stress along the slope exceeds the shear resistance, landslides and other mass wasting phenomena set in along the most vulnerable, critical, or the weakest surface and the slope is modified to new value of equilibrium (Zerube and Mencel, 1982)
Studies have shown that development of hill land can have serious irreversible effects on its immediate environment as well as the surrounding environment downstream (Lim and Lee, 1992). For example, hill land development has lead to environmental degradation culminating in environmental hazards and disasters. These include: the collapse of the of the Highland Towers luxury condominium (caused by landslide) in 1993 which claimed 49 lives; the Genting Highland landslide tragedy in July 1995 which killed 20 persons and injured 23 others; the Pos Dipang landslide which claimed 40 lives in August 1996 (mostly aboriginal living on steep hill slopes); the occurrence of 60 landslides in Penang in September 1995; north-south highway landslide near Gua Tempurung in January 1996 which claimed one life and caused massive traffic jams for weeks;; and most recently in October 1996, the spate of landslides in Cameron Highlands (a highland resort) in which one person was buried alive and hundred were evacuated.(Chan, 1998). These are but a few of the salient examples of classic environmental degradation resulting from human miscalculation and mismanagement of the forces of nature.
The whole of mass movement can be subdivided into three major classes: slides, rock fall and debris flows. The main differences between these three are in the way in which movement take place. In a slide, the movement material remains largely in contact with the parent or underlying rocks during the movement, which takes place along a discrete boundary shear surface. The term flow is used when the material becomes disaggregated and can move without the concentration of displacement at the boundary shear. Although a flow can remain in contact with the surface of the ground it travels over, this is by no means always the case. Lastly, falls normally take place from steep faces in soil or rock, and involve immediate separation of the falling material from the parent material, with moment involving only infrequent or intermittent contact thereafter, until the debris comes finally to rest. (Bromhead, 1986)
Introduction
Landslides belong to a group of geomorphological processes referred to as mass movement. Mass movement involves the outward or downward movement of a mass of slope forming material, under the influence of gravity. Although water and ice may influence this process, these substances do not act as primary transportational agents. Landslides are discrete mass movement features and are distinguishable from other forms of mass movement by the presence of distinct boundaries and rates of movement perceptibly higher than any movement experienced on the adjoining slopes. (Mariis, 2006)
Thus, this group of process includes falls, slides and flows.
Landslide hazards and disaster occur because human choose to occupy hazard zones, mismanage hazards, overdevelop land and deplete natural resources (forests and hill slopes) at a rate the changes of which the capacity of the natural system cannot cope with and adapt to. Increased in landslide characteristics (such as frequency, magnitude and extent) in many parts of Malaysia in recent years are directly related to the inability of disturb natural systems to cope with sudden changes inadvertently induced or deliberately carried out by humans. For example, clearing dense natural tropical forests without replacing them with sparse agricultural crops increases the erosivity of rain splash erosion and run-off erosion. (Chan, 1998)
Landslides pose a recurrent hazard to human life and livelihood in most parts of the world, especially in some regions that have experienced rapid population and economic growth. So, types of measures that can be taken to prevent the occurrence of slope failures include cut and fill solutions, rock and soil anchors, drainage, geogrids and retaining walls. These measures can directly reduce down the occurrence of slope failures in a way that hazard of slope failures can be minimized.
Literature Review
Deforestation on low land can cause erosion and sedimentation problems but not landslides. However, when it is carry out in hilling area, especially steep slopes of more than 20 degrees, it can be a catalyst to erosion and landslides. Controlled deforestation with immediate replanting can curb erosion and landslides but when it is carry out at a rapid non-sustainable rate, it can weaken slopes and bring about landslides. Deforestation is closely related to hill development as hills are usually forested before they are developed. Wan Ruslan Ismail (1994) has shown that deforestation can have adverse effects on the hydrological cycle in Malaysia, particularly that relating to increase in run-off and erosion. (Wan Ruslan Ismail, 1994)
Highway construction through the dense equatorial forests has also been a major cause of soil erosion and landslides. There have been numerous incidents of minor landslides along highways before the major landslide which occurred along the North-South Highway near Gua Tempurung in Bidor in 1996. In this landslide, an entire section of a hill slope collapsed and buried as section of the highway, killing one person. Since this incident, the Highway Authority PLUS has been told by government to check its slopes along major highways, and if necessary reinforced them. (Ahmad Chik, 1992)
Chan and Goh (1995) have shown that in a natural forest ecosystem, the rainfall has to pass through several processes which absorb part of the rainfall, reduces run-off and decrease the speed of the surface run-off. Thus, under natural forests conditions, only a portion of rainfall ends up as surface run-off, the majority of which is absorbed through water uptake by vegetation and soil water recharge. Dense tropical vegetation acts as a "sponge" which soap up much of the rain. On the other hand, under exposed conditions, almost the entire volume of failing rain hits the surface and flows on it as surface run-off in a short time duration. In an exposed area, the topsoil is destroyed and as vegetation which previously held the soil together is cleared, structural weaknesses then occur in the soil. (Chan and Goh, 1995)
In areas with steep slopes, such weaknesses will lead to landslides. Often, the occurrence of landslides precedes or accompanies that of floods as rapid flow of water into restricted channels (which also suffer ill-effects of situation from exposed land development schemes) result in too much water flowing into the river at too short a time and his exceeds the river's discharge capacity, often culminating in flash floods. (Chan, N.W., 1996)
A flow is a mass movement which involves a much greater internal deformation than a slide. The important characteristics of a flow could be obtained through movements taking place on a large number of discrete shear surfaces, or by the water content of the moving mass being so high that it behaved as a fluid, the latter being the case in clay soils at the water contents above the liquid limit. So soils will absorb water readily when disturbed, fractured and cracked by an initial landslide, and this leads to the sliding movements breaking up into earth or mudflows. (E.N Bromhead, 1986)
Slides are often translational in nature, i.e. they involve linear motion, especially if fairly shallow. A rock block may slide down intersecting joint planes which daylight in the face of a cutting, or a block may move down a steeply inclined joint or bedding plane. Where such a block is joint-bounded on its sides, a lateral thrust from water filling some of the joints can push a block even along a low- angle surface. (E.N Bromhead, 1986)
A fall of material, soil or rock, is characteristic of extremely steep slopes. The materials which moves can break away from the parent rock by an initial sliding movement: some shear surfaces may develop in response to gravity stresses and, in moving, the material is projected out from the face of the slope. Alternately, due to undermining at a low level in the slope, an overhang may form. Then, either because the rock is jointed, or because it has insufficient strength en masse, there comes a point at which the undermining causes a fall to occur. When a fall occurs, the material involved will break up: if not while in motion, then on impact. (E.N Bromhead, 1986)
Anchors in soil and rock slopes can be of two types: they can be unstressed and rely purely on a dowelling action to increase the resistance for sliding; or they may be stressed. In this latter type, the axial load in the anchor increases the effective stresses at depth in the soil or rock, improving strength. A vector component of the anchor force may also act to reduce the destabilizing forces and moments. (E.N Bromhead, 1986)
The term 'counterfort drain' is sometimes used to describe trench drains which penetrate into solid ground below the soil which is being drained, and may therefore provide some mechanical buttressing effect as well as their effect on the pore water pressure and hence shear strength in the drained soil. The major use of these trench drains is to stabilize shallow slides and slides of a principally translation character. In these type of slide it is often totally impractical to attempt extensive regarding. Often, the landslide may involve highly disturb soil, mudslide debris or a solifluction sheet, which will have a much larger permeability than underlying undisturbed soil. The seepage pattern in the landslip debris, in between the drains, can then be treated as having an impermeable base.
(E.N Bromhead, 1986)
Geogrids are synthetic soil-reinforcement materials. Typical of these is Tensar, which is manufactured by punching a regular pattern of holes in a sheet of plastics material, and then stretching it to orientate the long chain molecules in the plastic material. The resulting grid can then be incorporate into an embankment fill. The first of these is to consider the reinforcing grid as an anchor. In contrast, a potentially more useful feature of geogrid reinforcement may be used in the control of ground strains, reducing the likelihood of progressive failure in brittle soils, or of excessive plastic deformation in weak foundation materials. Goegrids have also been used effectively to repair small slides in engeneering earthworks. (E.N Bromhead, 1986)
Problem Statement
As a result of rapid economic development in our country, physical systems are disturbed and changed. For example, the modification of the hydrological cycle due to deforestation, urbanization, development of hill slops and other human land use have given rise to increased risks of landslides. In recent years, the collapse of a block of luxury condominiums in Kuala Lumpur, Genting Highland and Pos Dipang landslide strategies as well as other landslide disasters have caused substantial loss of life and damage to property and infrastructure. (Chan, 1998) Thus, the safety of our living environment becomes the major aspect of the development that need to equip with to fulfill the safety of human life. As a result, measures of slope stabilization would be a better solution to prevent this problem.
Aim
To conduct a study into the slope stabilization methods that can be used to prevent the occurrence of slope failures.
Objectives
To find out the causes of slope failures and how it occur in our country.
To find out the types of slope failures.
To establish more details study on the slope stabilization methods that can be used to solve this problem.
Research Question
What are the factors that trigger slope failures in Malaysia?
How many types of slope failures existed?
What are the measures that can be used to solve this problem?
Research Methodology
To ensure the validity and accuracy of this study, I will try to get the information from a lot of resource. The methods in collecting the information are classified into two categories which are primary and secondary sources.
For the primary data, the case study method will be choosing in order to collect the required information because this method is more reliable and precise if compared to other methods. Case study enables researcher to have a direct observation into the project. Thus, information can be collected by direct observing the site condition. The data such as causes of slope failures and the prevention methods can be determined. Thus, a stabilization method can be mapped out due to the suitability in order to solve the problem effectively.
For the secondary data, this study will comprehensive review some of the literatures which are related to the slope failure, the causes and prevention methods of slope failures. The information gets from the secondary data normally through article, journal, reference book, magazine, newspaper and thesis. All of this information is obtained from internet, library and book store. Besides that, the college e-learning also provide many relevant information regarding slope failure to continue my research.
Anticipated findings and contribution
This research will enable me to find out the factors that trigger the occurrence of slope failure in our country. Massive hill developments like deforestation, quarrying, housing development, highway construction and farming at hilling areas without proper planning and management have directly caused slope failure to happen. Meanwhile, after read through the journal, I am found out that mostly of the slope failure can occur in different ways in response to the types of soil as well as the location of the places. Meanwhile, the tragedies of slope failures in our country can also be knew after read through the related journal.
Besides, effects caused by slope failure bring a lot of damages to property and environment as well as human lives. Thus, the effective management in controlling this problem can be justified in the research. The measures can be in term of structural (engineering based measures) as well as non-structural (non-engineering measures) which can be employed to prevent this incidence. This research will contribute to reduce the occurrence of slope failures.
Working program and timetable
Task to be completed
Week
1
2
3
4
5
6
7
8
9
10
11
12
13
Briefing about research
methodology
Finding the research topic
Meet with supervisor and
finalise a research topic
Searching for related article
Prepared proposal outline
Typing down propasal item
accordingly and systematically
Prepare presentation slide show
Presentation of research topic
and submission of first draft
Prepare final draft
Submission of final draft
Overall Structure and Planned Organisation of Dissertation
Chapter 1 Introduction
This chapter is an introduction to the slope failures. In this chapter, it will look into the aims, objectives, hypothesis, and problem statement, background, importance and benefits of the study, scope of study and methodology of the research.
Chapter 2 Literature Review
This chapter will explain the objectives of the research. The relevant information will be collected from primary data and secondary data. From the primary data such as journal, article, reference books and internet, I will able to find out the information that related to the causes, types of slope failures and the prevention method available. On the other hands, secondary data such as case study and interview, it helps to get better understanding on the types of measures used to prevent slope failures.
Chapter 3 Research methodology
Case study will be conducted to collect the data that contribute to my research. From the case study, I can research in depth to the objectives and thus I gain my knowledge in doing this study.
Chapter 4 Data Analysis
The data collected will be analysed and presented in a table or graph. Data analysis can be the comparison between two case studies. Therefore, the data analysed and the result presented will help the findings present in a more concise way.
Chapter 5 Conclusion and Recommendation
This chapter is to conclude the overall dissertation. The aims, objectives, hypothesis and problem statement that established in the Chapter 1 will be identified. After that, some recommendation will be introduced to make an improvement to this study.
