ABSTRACT: Rapid urban development in the hilly terrain of Hong Kong involves the construction of high-rise buildings, many of which are supported on large diameter bored piles. These piles may sometimes have to be founded in slopes and have to resist severe wind loads during typhoon season. In order to minimise the transfer of lateral load from the buildings to the shallow depths of the slopes, an annulus of compressible material (referred to as sleeving) has sometimes been incorporated between the piles and the adjacent soils. In this paper, three-dimensional (3D) numerical analyses were carried out to examine the interactive effects of sleeved piles on slope stability. In the case of a single pile in a slope with a respectable safety margin, the sleeving technique is shown to be capable of minimising the adverse impact of lateral pile loading on local slope instability compared to an unsleeved pile, particularly under high lateral loading. In the case of a marginally stable slope which is vulnerable to external loading, whether the single pile is sleeved or not would make little difference to the global factor of safety. INTRODUCTION Rapid urban development in the hilly terrain of Hong Kong involves the construction of high-rise buildings, many of which are supported on large diameter bored piles. These tall buildings have to resist severe wind loads during the typhoon season each year. Local instability may be associated with the initiation of plastic deformation at the shallow ground in front of the laterally loaded pile, with development of successive cracks being likely to occur in sand (Uto et al., 1985), and large plastic deformation being likely to occur in clay. Global failure may occur if the soil mass supporting the pile develops a slip surface, accompanied by uncontrolled large displacements.

ABSTRACT: In this study, we at tempted to develop methods of evaluating and predicting the risk of failure of rock beds and slopes facing roads in order to improve the efficiency of road disaster management under the limited funds and man power. INTRODUCTION Some areas of Japan face severe topographical and climatic conditions. Therefore, counter measures against natural disasters to ensure safe and reliable conditions throughout the country are indispensable for providing stability to people–s lives and ensuring the sustainable growth of the economy. Roads are a basic social infrastructure, however due to topographical reasons, are often constructed in close proximity to unstable rock beds and slopes that are vulnerable to collapses and failures. Road administrators have implemented disaster prevention measures against failures of rocks and slopes, but more than 100,000 sites still require such disaster prevention measures or management system based on daily inspection. There had been a resistance to active implementation of the concept of risk management in the field of disaster prevention managed by public sector. The reason for this was that administrators were apprehensive about being held responsible for any risk in the facilities controlled by the government, such as roads an driver levees, by disc losing the risk to the public. There is a possibility that the occurrence of negative events is has tally connected to administration errors, as is pointed out by Okada and Kobayashi (1993). However, in order to undertake more effective and efficient road disaster management under the limited funds and manpower, it is necessary to develop the risk evaluation and management technologies that can clarify the effects of disaster prevention investment and improve public accountability. This study therefore attempts to develop methods of evaluating and quantifying the risk of failure of rock beds and slopes in road disaster management.

ABSTRACT: After heavy rainfall at Kangchon-Ri in Korea on 27 July in 1996, an excavated and reinforced slope for condominium construction site was failed. To figure out the cause of the slope failure and to plan remedial works, investigation of rainfall, surface and subsurface geological surveys and monitoring of the slope behavior were carried out. According to this investigation the remedial designs and works were performed. This paper describes the cause of the slope failure, the design and construction of remedial works and the monitoring of the slope behavior after the remedial works. INTRODUCTION The wet season from June through August in Korea is characterized by heavy rainfall. Mt. Kumbong is located at Kangchon-Ri, Choonsung-Gun, Kangwon Province in Korea. An approximately 80m high rock slope in the mountain has been excavated for condominium construction and reinforced with prestressed anchors. There was heavy rainfall in this area after the completion of excavation and reinforcement. Progressive failure occurred in the prestressed anchors with about 30% of the installed anchors broken. Tension cracks and main scarps occurred 60m behind the crest and the former occurred within the excavated slope. A series of investigations to assess the cause of the slope failure such as relationship between rainfall and slope failure, geological survey of surface and subsurface and monitoring of the slope behavior, was carried out. According to the investigation, remedial design and remedial works including instrumentation were performed. This paper describes briefly the investigation, remedial design, remedial works and monitoring results after remedial works. STATE OF THE SLOPE FAILURE Slope failure started from the breakage of anchors. The breakage of the anchors began at the left, center, and right parts of the slope and 30% of the total 284 anchors were broken.

ABSTRACT: Acoustic Emission (AE) is one of the nondestructive techniques, which is known as elastic waves generated due to crack initiation, crack formation and crack coalescence. Because AE is known as effective and sensitive for evaluating rock stability, a variety of research papers on AE application to rock monitoring have been reported (Goodman and Blake, 1966; Hardy, 1981; Nakajima et al., 1988). Although great deal of works were carried out in respect to AE monitoring in rock, successful results to evaluate and predict slope failure are quite few. This is partially because AE sensors are usually set in the vicinity of rock surface. To expand monitoring area, AE sensors of such lower resonant frequency characteristics as less than 10 kHz are employed. These surface setup and lower frequency characteristics of AE sensors easily bring remarkable amount of undesirable AE events due to natural phenomena. Since the frequency characteristics of AE waves ranges around 10 kHz (Shiotani et al., 1999c), it is difficult to eliminate such noises from AE data acquired. Moreover, in the case of monitoring rock failure, it is further difficult to completely take into account the state of the pre-existing joint properties, although several surveys on rock characteristics and joint conditions are performed prior to AE monitoring. Because AE waves generated within rock are normally reflected at the joints when they propagate, the existence of the joints would be a great problem to detect AE waves efficiently. Thus, it is necessary for AE monitoring in rock to develop an effective method for detecting AE waves which are not dominantly influenced by such conditions as natural noises and existing joints. In the paper, an installation method of AE sensors for AE monitoring in rock called WEAD is developed.

ABSTRACT: Post-mortem analyses of seven slope failures in rock slope are reported. The analysis is based on simple force equilibrium of a block of rock surrounded with several planes of discontinuity and separated from the neighbouring rock mass in a rock slope. Driven by the own weight of the rock block together with the ground water pressure acting on the planes of discontinuity, the stability of rock mass is maintained by the shear resistance of the materials embedded in the thin clearance forming the slip surface. A slope failure takes place when the shear strength is not strong enough to resist the driving forces. Seven case studies indicate that the simple principle of three dimensional force equilibrium is good enough to estimate the factor of safety in the slopes of rock mass containing the cracks filled with soft clayey materials. INTRODUCTION Rock slope failures are often triggered by the unusual rise of the ground water level caused by heavy rainfalls or rapid snow melting. Rock masses usually contain a number of discontinuities such as cracks and fissures that may become potential slip surfaces especially when thin seams of soft clay lies within them. This paper presents the post-mortem stability analyses of seven sites where slope failures took place. Undisturbed samples taken from the clay seams which happened to play a role as the slip surfaces are subjected to shear box tests under conditions of constant volume during shear. The driving forces in such a category of rock slope failures arise from the own weight of the rock mass as well as from the water pressure acting on the discontinuity planes around the sliding rock mass. The resisting forces arise from the shear resistance of the clay seams lying along the slip surfaces.

ABSTRACT: Remedy of slope failures along mudstone surfaces requires proper understanding of the shear strength characteristics of that material. Results of studies show that the residual strength of mudstones could be as low as 10 degrees in terms of the effective internal friction angle. Depending on the height and the geometry of the slope, stabilization measures include earth buttress, stabilizing berm, pile wall and anchored wall. This paper presents case histories on the application of the above-mentioned measures. INTRODUCTION The Second Northern Freeway is a major transportation development in the northern Taiwan. Extending from Hsihchih to Hsinchu, this 6-lane freeway is 117 km in length. The route comprises 20 interchanges, 40 km of viaduct sections, 8 km of mined tunnels and 70 km of earthwork sections. The construction commenced in 1987 and the freeway became fully operational in 1997. The route runs through the north portion of Western Foothills Area in Taiwan. Major rock formations along the route are composed of the Cholan formation of the late Pliocene and the Toukoshan formation of the early Pleistocene epoch. There are tectonic faults and folds located in close proximity to the route. The Cholan formation is mainly composed of sandstone intercalated with mudstone. The mudstone layer generally has a thickness of less than 1 m. The ground surface is generally covered with a mantle of yellowish brown, highly to completely weathered, sandstone or mudstone which has the thickness of about 10 m. It is commonly recognized that as long as a weak discontinuity of the rock is exposed during excavation, and that the discontinuity is dipping in the same direction as the slope, the overlying block has the tendency of sliding along the weak plane. Provisions of positive preventive measures at the design stage can avoid these unstable conditions.

ABSTRACT: Izumi group is a mass of geological strata made basically of sandstone and shale. It is distributed near the southeastern part of Japan and mainly spreads all along the north side of the Median Tectonic Line in Shikoku Region. As expressway in this region is built nearly parallel to the tectonic line, a number of cut slopes in Izumi group suffered a failure despite a very gentle slope angle of about 34o. Observation of the failure pattern and the slope soil characteristics revealed that most of the failed slopes consist of medium hard rocks, whereas many slopes consisting of weathered soft rocks were stable. This typical failure pattern was considered center point of the study in this paper. Soil samples were collected from different cut slope sites of all the three states of soil, i.e., hard rocks, medium hard rocks, and weathered soft rocks. Strength and x-ray diffraction tests were carried out to elucidate the slope failure mechanism. Test results revealed that the shale rock has a small angle of external friction, far smaller than the angle of shearing resistance, and its bedding planes at failure sites make a positive acute angle with the horizontal plane. INTRODUCTION Izumi group in Japan represents the geological strata distributed in southeastern part of the country. Owing to tectonic movements, most of the rocks along this line are in a fractured state that has caused a fragile geology in the area. This fragile geology has resulted in a number of landslides and slope failures, especially during and after the construction of Tokushima-Matsuyama Expressway that has been aligned along Izumi group and the MTL. Izumi group is supposed to have formed by an alteration of sandstone and shale some 64 to 100 million years ago during cretaceous period.

ABSTRACT: A stochastic slope stability method based on a total stress approach is presented with an application to a well - documented experimental excavation site. Undrained strength values are model led as outcomes of a stochastic process. This permits to reproduce the random nature of measured soil properties and the associated spatial variability structure. Variogram analyses indicate that a Stationary Random Function of the second order yields a satisfactory model for spatial variability. Using this model, virtual undrained strength fields that are conditioned to available field measurements are generated through a sequential gaussian simulation technique. Stability analysis for a given slope geometry is then performed for each generated virtual field of a series. This creates a set of factors of safety (Fs) which are realisations of the Fs random variable (RV). These results are then compared to actual field conditions where slope failures have or not been observed. Results show how statistical parameters such as average factor of safety and failure probability are dependent of the geometry of the slope and of the neighbouring conditioning undrained strength profiles. INTRODUCTION The common approach in designing a slope against slide failure is to adopt a set of design parameters and compute a factor of safety (Fs). Selection of a target value for the factor of safety is made in view of the understanding and knowledge of subsoil nature and in particular its variability, problem geometry, and consequences of failure. This design approach is said to be deterministic since it is based on a fixed set of input variables, yielding a unique output for the factor of safety. Although as can be seen, the way design target values are selected is strongly influenced by the stochastic nature of many input variables.

ABSTRACT: A series of laboratory slope failure experiments was conducted to elucidate the initiation of rainfall-induced slope failures from moisture content measurement records. The change in moisture content during the infiltration of rainwater and at initiation of slope failures was monitored by moisture sensors (Amplitude Domain Reflectrometry type). Prior to experiments, numerical unsteady seepage analyses were also conducted to identify the hydraulic response of the soil slope models to rainfall. The experiment results showed that slope failures were initiated by the increase in moisture content of the soil at the toe of the slope. Moisture content of the soil was noted to reach its saturated value at the time of failure. This indicates that rainfall-induced slope failure is a consequence of instability of the toe of the slope induced by saturation process under drained condition, and the major portion of the sliding mass may still be in an unsaturated condition. The experiments reported in this Paper also indicated that the direct measurements of change in moisture content could provide a great possibility in predicting the critical time of the initiation of rainfallinduced slope failures. Therefore, the results of applying any moisture sensors to predict and to monitor slope movements are encouraging. INTRODUCTION Rainfall-induced slope failure is one of the most destructive natural hazards, which can occur in a matter of seconds, and without warning during a prolonged heavy rain. Most slope failures always take place annually in Japan during the rainy season in the month of June when the rainfall intensity can reach up to 100 mm/hr. The disasters have claimed untold numbers of human lives and million dollars in infrastructure losses every year in many parts of the world. In Indonesia, for example, during the last eight years, there have been about 537 lives lost due to slope failures.

ABSTRACT: The stability of slopes characterised by colluvium presents major challenges to developers, engineers and government authorities. The risk of slope failures is higher in areas characterised by high altitudes and high intensity and prolonged rainfalls. Unfortunately, the routine methods of geotechnical investigation and analysis normally adopted for steeply sloping sites may not be applicable, largely due to the composition and characteristics of colluvium. Practical experience and innovative engineering is therefore required. This paper presents a discussion on the available site investigation techniques for assessing colluvium slopes. The usefulness of in situ and laboratory tests is reviewed, together with the applicability of the derived soil parameters for the engineering analysis. The effects of rainfalls on the stability of a slope and precautionary measures for ensuring adequate long-term stability are discussed. INTRODUCTION Scarcity of suitable development lands within metropolitan areas, and unique views offered by mountainous regions are among contributing factors to hillside developments in many parts of the world. Unfortunately, such regions are usually associated with potential slope failures. The risk of slope instability is significantly increased where the site is characterised by colluvium. There is a general tendency to classify sites characterised by colluvium as unsuitable for residential development. In Australia, and the Gold Coast in particular, the process of site classification by the residential slabs and footings code (AS2870, 1996) may preclude the identification of the presence of colluvium. If appropriately engineered, the presence of colluvium may not preclude development. However, there could be drilling rig accessibility problem due to site topography. Also there could be exploration difficulties associated with subsurface characteristics and material composition of the colluvium. ORIGIN AND CHARACTERISTICS OF COLLUVIUM Lansford (1999) described colluvium as landslide debris, which has slowly accumulated, on the long slopes of mountains

ABSTRACT: Field and laboratory investigations as well as slope hydrodynamic simulations were carried out to observe the mechanism of landslide at Puncak Area in West Java, Indonesia. Monitoring on water level fluctuations in piezometers were conducted to calibrate the simulation results. It was found that the inducement of landslide was started from the lower part of middle slope. The seepage from upper slope as well as back-up migration of saturation front in response to rainfall played an important role in triggering the slope failure. Indeed, the largest increment of pore water pressure occurred in blue clay under the lower part of middle slope in which the failure surface developed. INTRODUCTION Landslide occurred at Puncak area in West Java, Indonesia (Figure 1) in February 1984 after the heavy rainfall and destroyed a highway section as well as several houses. Such landslide was located at the lower part of Mount Megamendung (Figure 2) and resulted in the translational movement of colluvial deposit (clay - silt layer), and sand layer (Figure Ib). These deposits were underlain by blue clay which was investigated as the failure surface (Sugalang, 1989). Such clay was montmorillonite and interpreted as the lake deposit, originated from tuffaceous sediments (Karnawati 1999). FACTORS ENCOURAGING PUNCAK LANDSLIDE According to field observation as well as the evaluation on geological data and rainfall record, the interaction of rain precipitation, morphology, geology, hydrogeology, and existing landuse conditions were considered as factors encouraging landslide. The landslide occurred on a gentle slope which was only about 15 0 (Figure 5), when the monthly precipitation was high (exceeding 770 mm as illustrated in Figure 3). This gentle slope should be stable, however it was located on the foot of mountains which was surrounded by higher mountainous and hilly morphology (Figure 2).

ABSTRACT: Compacted clay fill is a widely accepted construction material with measurable properties and predictable performance. This paper explores weakening of an adequately compacted clay fill that resulted in slope failures. Raby Bay Canal Estate is situated on the southeast Queensland coastline as a staged development of cut-to-fill earthworks in high plasticity clay soils. Final canal banks consist of various zones of compacted clay material overlying residual clays. Revetments consist of low concrete retaining walls with rockfill mattresses extending down to lowest tide level. During construction some failures occurred during excavation of slopes in fissured residual clays. More widespread post-construction slope failures have occurred in several stages of the estate, with repairs including piled support for the concrete walls. Initially there was reluctance to accept that these failures developed in compacted clay that had passed testing in accordance with specifications. Investigations were undertaken to identify weakening and potential future failures, with field and laboratory tests including simple wetting-up procedures. The processes leading to failure are not completely understood but involve clay mineralogy, initial fabric, and drying and wetting effects on plasticity. The constructed slope batter angle is almost identical to the softened peak friction angle, while the residual friction angle is significantly lower. The as-compacted clay fill fabric must be virtually free of defects, which is not easy to achieve at edges and between layers using typical construction specifications. INTRODUCTION Many residential canal estates have been developed along the southeast Queensland coast, a region of rapid population growth and urbanisation. During and since this time there have been several areas of canal bank failure, some during construction but many developing after several years. The local government authority maintains the canalside of the concrete headwalls of the revetments, and was concerned about potential future failures.

ABSTRACT: Debris flows and slope failures have frequently occurred in the Ryugamizu cliff, located in southern Kyushu, Japan, during every rainy season. Gushing of groundwater from the cliff slope and rapid increasing of discharge rate in ravines just after a series of heavy downpours are major factor for triggering the debris flows in this area. The cliff is composed of various volcanic and pyroclastic rocks with thin sedimentary layers, which form hydrogeological anisotropy. Because top of the cliff is topographically low relief, such groundwater is mostly supplied from the rainwater on the top. To obtain effective warning indices for the occurrence of debris flows, rainfall, groundwater depth, and discharge rate in ravines have been monitored, and the relationship between them has been analyzed in addition to determining hydrogeological conditions of the cliff. Expressing the relationship as a simple tank model, temporal changes of the discharge rate can be estimated from the records of 10-min rainfall and groundwater depth. Assuming a proper threshold value of discharge rate, a combination of values of rainfall and groundwater depth may become an effective warning index for the occurrence of debris flows. INTRODUCTION Frequent occurrence of debris flows during every rainy season is one of socially serious problems in monsoon affected countries including Japan. They result in large damages to houses, roads and railways, and sometimes loss many lives. To mitigate such damages due to debris flows, constructing effective systems or indices for warning has been required for the government and people living there. The Ryugamizu cliff located in southern Kyushu, Japan (Figure 1) is one of such regions. Debris flows frequently occur in poorly dissected ravines from June to September. On Since the disaster, the governments and traffic agencies have required to establish more effective indices of warning for the occurrence of debris flows.

ABSTRACT: Southern Thailand was subjected to an intense rainfall in November, 1988. This rainfall triggered thousands of slope failures in the Khao Luang Mountain Range and caused widespread flooding in southern Thailand. The landslides, debris flows and flooding caused the deaths of 370 people and damage to properties estimated at about US$ 300 million. Landslides and debris flows are expected in the Khao Luang Mountain Range because of the disturbed slope materials, land-use pattern, intense seasonal rainfall and the geomorphic development in the area. This paper investigates the mechanism of debris flow initiation in the Lham Nah Creek Basin (Study Area) in the Khao Luang Mountain Range by analysing the properties of materials involved in debris flows. INTRODUCTION Southern Thailand, particularly the Khao Luang Mountain Range, was subjected to an intense rainfall during the period 19th to 23rd November, 1988. This rainfall triggered thousands of slope failures in the Khao Luang Mountain Range and caused widespread flooding in southern Thailand. The landslides, debris flows and flooding caused the deaths of 370 people and damage to properties estimated to be in the order of US$ 300 million (HANSON, 1989). The location of the Khao Luang Mountain Range, rivers emanating from the mountain range and places severely effected by landslides and debris flows during November 1988 storm are shown in Figure 1. Landslides and debris flows are expected in the Khao Luang Mountain Range because of the disturbed slope materials, land-use pattern, intense seasonal rainfall and the geomorphic development in the area (HANSON, 1989). If adequate mitigative measures are not implemented, the casualties and cost of possible future landslides and debris flows are likely to be very high. The risk is increased because of population growth and economic developments in the area.

ABSTRACT: Landslides are a common feature of the basalt terrain or north eastern New South Wales. Failures typically occur through residual soil layers, at strength between the peak soil substance strength, and typical residual strength values. Shear strength on soil fissures approach residual strength. Failure therefore seems to occur through a combination of turbulent or rolling shear of the soil substance and sliding shear on fissure surfaces. Fissure properties such as surface condition continuity, spacing and orientation need to be observed when investigating sites in the area, or in similar geological terrains to allow consideration of the likely influence on overall soil mass strength. INTRODUCTION North eastern New South Wales is a region of rapid growth. The geology of the region consists of an accumulated sequence of interlayered basalt flows, overlying Tertiary/sediments, sedimentary rocks, minor volcanics, and a metamorphic basement. Mass movements are common on the slopes surrounding the remnants of the basaltic shield resulting in urban development, and major transport and communication links being constructed on potentially unstable slopes. Two predominant soil groups have formed from the basaltic rocks, the pedalferic krasnozem soils, and the pedovocalic brown soils. The krasnozems are locally referred to as ‘red’ soils, and are generally found to the east of Lismore. These are strongly structured clay soils with little horizon differentiation. The brown soils occur predominantly to the west of Lismore and are characterised by chocolately brown colour, and a clayey, cohesive texture and often heavily fissured structure. The boundary between the eastern and western soil types is sharp, and correlates well with rainfall patterns. The purpose of this study was to evaluate data from twelve case study sites, with the aim of identifying mechanisms of strength loss in the soils, and slope processes which work to promote strength loss and ultimately initiate failure.

ABSTRACT: Slope cuts in granitic bedrock areas expose weathering profiles that can be differentiated into three broad morphological zones. The topmost Zone I comprises stiff to very stiff, gravelly sandy clays with indistinct relict bedrock textures, whilst the middle Zone II consists of medium to very dense, gravelly silty sands showing distinct relict textures and structures, and also containing coreboulders. The bottom Zone III of bedrock only shows effects of weathering along and between structural discontinuity planes. At steep cuts and benches (> 60o) exposing Zone I, small earth falls and shallow slips can occur during rainfall due to saturation and loss of strength with time. At steep benches (> 55o) exposing Zone II with day-lighting relict discontinuity planes, wedge failures can occur due to saturation and low shear strengths. During periods of intense or continuous daily rainfall, slumps, slump-flows and debris flows can occur at moderately to steeply sloping (> 45o) cuts exposing Zones I and II, as a result of rainwater induced saturation and loss of suction within the slope materials. Where steep benches (> 55o) expose Zone III, block slides, slab slides, wedge and toppling failures can occur as a result of favourably oriented discontinuity planes having low shear strengths. Rock falls occur where the bedrock is closely fractured. INTRODUCTION Deep weathering profiles are found over granitic bedrock in Peninsular Malaysia as a result of favourable environmental and tectonic conditions that have facilitated intense and pervasive chemical weathering (Raj, 1982). These profiles are found in undulating to hilly and mountainous areas and are well exposed at slope cuts excavated during the construction of transport routes. Prior to these discussions is a generalized description of the earth materials into which the cuts are excavated by reference to a typical weathering profile developed over granitic bedrock.

ABSTRACT: In September 1998, a natural slope failure in weathered sedimentary rocks occurred in Mt. Keummu, which is located at the southeast part of the Korean peninsula, due to the heavy rainfall. To find general characteristics of the natural slope failure, detailed geological survey, ground penetration radar (GPR) investigation, two boring tests, laboratory tests, and analyses using commercial computer programs were performed. The site is composed of sandstone, conglomerate, and shale, and the sliding surface is developed along the bedding plane. The ground penetration radar prospecting and boring tests confirmed that the location of the sliding surface near the head of sliding mass is at 3.3m. Based on the result of computer analyses it is concluded that the slope becomes unstable when the ground water table rises near the surface by heavy rainfall. A planar failure along one of the joint sets is also expected when the angle of internal friction is less than 20°. The effect of construction of an access route for forest watch is minor, and high water table is found to cause considerable displacements, especially at the toe of slumped mass. INTRODUCTION In Korea, natural and excavated slope failures are one of the leading natural disaster types that result in the loss of human lives; 103 persons died by landslides in 1998. This number indicates that 26.8% out of a total of 384 natural-disaster-related deaths were caused by the slope stability related problems. Most of the landslides occurred during the period between July and August; part of the monsoon season. The majority of the landslides during this period can be categorized as flow type. A geological survey, ground penetration radar (GPR) prospecting, two boring tests, laboratory tests, and analyses using commercial computer programs were performed.

ABSTRACT: Urban geology relates to the application of geological studies to urban development. The role of geology in urban development cannot be over-emphasised. The development of urban centres and its associated problems are dictated by and large by the geologic settings of the areas concerned. In Malaysia, this is clearly illustrated by the major urban centres in the country, such as the capital city of Kuala Lumpur, Ipoh, Penang, Kuantan, Johor Baru and Kuching. This paper discusses and provides a comparative study of the urban geology of these six major urban centres in Malaysia. Kuala Lumpur and Ipoh provide good case studies on the influence of geology on urban construction and development. As both cities have rather similar geology with limestone as the dominant bedrock, construction problems and associated geohazards such as subsidence and sinkholes are strikingly similar indeed. In contrast, Penang is underlain by granitic rocks which form hilly terrains - thus it experiences marked landslide, rockfalls and other slope instability problems associated with hillside development. In the case of Kuantan where large areas are covered by basaltic soils forming low, undulating hills, landslide problems are minimal. Johor Baru, on the other hand, has the Old Alluvium as a unique soil deposit underlying much of the city and vicinities. The Old Alluvium forms mostly low-lying hillocks and has been sourced for construction fill materials. Finally, the East Malaysian city of Kuching lies on mainly flat, alluvial plains and peat swamps and has to contend with soft soil problems (consolidation settlement, etc.) and river-bank instability problems. Nevertheless, the few small hills in Kuching which are underlain by sedimentary rocks and river terrace deposits have been the subject of recent studies on slope instability/slope failures as water reservoirs or storage tanks are sited on these hills.

ABSTRACT: Mechanisms of slope movements are always the result of a complex stress-strain field induced by factors depends on soil properties and initial conditions and is categorised by different landslide styles. The major aim of this report is to stress the relationship existing between mechanisms and mechanics of slope movements induced by changes of boundary conditions. FOREWORD The word mechanism in the context of slope stability is generally used to describe the modes of deformation and rupture of slopes. It is hence essentially related to geomorphological features of slopes and to their changes induced by movements. For this reason, even if devoted to the mechanisms of slope movements, this paper is also mechanically based, because it deals with the quantitative stress-strain-time response of slopes to changes ofi i) stress boundary conditions (e.g. by erosion, static and dynamic loading or unloading etc.); ii) hydraulic boundary conditions (e.g. by rainfall, snowmelting etc.); iii) environmental conditions (e.g. by weathering, climatic changes, infiltration of pollutant waters etc.), which determine a change of soil properties. To stress these aspects, in this report the word mechanics will be also widely used. The main topic of the report is the relationship existing between mechanisms and mechanics of slope movements in fine grained soils (stiff fissured or jointed clays, clay shales and indurated fine grained soils, as mudrocks, degradable marls etc.). In particular, it will be shown that the main landslide styles described by well known geomorphological classifications (slides, earthflows, spreads etc.) have a bearing in the mechanics of processes which develop as a consequence of changes of boundary conditions. This goal will be pursued through examples, sometimes taken from the experience of the writer, concerning well documented cases of landslides, numerical analyses of slope behaviour and any other element useful to clarify such a relationship.

ABSTRACT: Rock slopes with heights approaching 1000 m are now being designed and excavated in various open pit mining and civil engineering projects around the world. The economic impact of excessively conservative designs or of failures in these slopes can be very large and every effort has to be made to optimise their design. Their size means that they will almost always contain a number of significant structural features and a variety of geological materials. The input required for these models includes a comprehensive geological data base that contains both structural geology and lithological information, an hydrogeological model that permits water pressures to be estimated throughout the slope, estimates of rock mass and discontinuity strength and deformation properties and an understanding of external forces, such as those due to earthquakes, that may be imposed on the slope. Site investigation techniques that can be used to obtain this information and the methods, that can be used to estimate rock discontinuity and mass properties, are reviewed in this paper. Developments in limit equilibrium and numerical modelling techniques are reviewed and their applicability to the design of these large slopes is presented. Practical examples from large projects around the world are presented. 1.0 THE GEOLOGICAL MODEL A comprehensive geological model is absolutely fundamental to any slope design. Without such a model, slope designers have to resort to crude empiricism and the usefulness of such designs, except possibly for very simple pre-feasibility evaluations, is highly questionable. In open pit mining a great deal of effort is devoted to defining a reliable geological model in order to quantify ore reserves. Therefore a reliable geological model exists and, provided that there is good cooperation between the geological and geotechnical departments of the mine, a small amount of additional effort will produce a sound geotechnical model.