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ROCK FALL HAZARD ASSESSMENT AND RISK ZONING OF GUUNG PONDOK, PADANG RENGAS, PERAK

NATURE OF PROJECT: ROCK FALL HAZARD
CLIENT: PERAK HANJOONG SIMEN SDN BHD
LOCATION: PADANG RENGAS, PERAK

INTRODUCTION

Gunung Pondok consists of limestone that could give the risk to the people who live close to the hill. There are several villages nearby the east hill of Gunung Pondok namely Kampung Sungai Ati, Kampung Pondok, Kampung Pulau, and Kampung Padang Rengas.  Light Detection and Ranging (LiDAR) and geological field survey were conducted to assess the physical characteristics of the Gunung Pondok (east hill). The LiDAR field data acquisitions were conducted using Terrestrial Laser Scanning (TLS) and Unmanned Aerial Vehicle (UAV) method. The geological discontinuities mapping, and identification of rock material were conducted using the scanline method and Point Load Index Tests at three outcrops, namely GP1, GP2, and GP3. The surveys were performed from 9th to 22nd September 2016. 

Figure 1: Gunung Pondok Hazard Hill
Figure 1: Gunung Pondok Hazard Hill
Figure 2: Site condition of Gunung Pondok for TLS data capturing
Figure 2: Site condition of Gunung Pondok for TLS data capturing

RESULTS AND DISCUSSION 

i) LiDAR Survey

LiDAR survey that was conducted provides the Digital Elevation Model (DEM) of the hazard hill. Several factor maps were generated such as hillshade map, elevation map, contour map, slope gradient map, slope aspect map as well as aerial photograph. These maps were used in rockfall trajectory analysis to visualize the running distance of the rock. Based on the LiDAR survey, a natural hazard hill estimated dimension of the total unstable rock mass being 100m long, 110m wide and 80m height with estimated weight of 2.38 million ton of limestone rock.   

 

ii) Discontinuity Mapping and Kinematic  Analysis

Discontinuity mapping and kinematic analysis conducted to determine the behavior of rock discontinuities (bedding, joint, fault) that effects the stability of the hill. The potential failures at the site were wedge failure, planar failure and toppling failure. Two (2) cavities were also identified near the base of hazard hill. The results of the analysis utilized in rock mass classifications based on Slope Mass Rating (SMR) method.  

Figure 3: Location of outcrop GP1, GP2 and GP3, Gunung Pondok, Padang Rengas Perak
Figure 3: Location of outcrop GP1, GP2 and GP3, Gunung Pondok, Padang Rengas Perak

iii) Slope Mass Rating (SMR) 

Slope Mass Rating (SMR) assessment was conducted utilizing the results from kinematic analysis, discontinuity mapping and point load test. Based on the analysis, the probability of failure of the slope ranged from 0.2 (stable) to 0.9 (completely unstable).  

Figure 4: Slope stability distribution at eastern hill of Gunung Pondok, Padang Rengas, Perak
Figure 4: Slope stability distribution at eastern hill of Gunung Pondok, Padang Rengas, Perak

iv) Rock Fall Trajectory and Hazard Zoning

The 875m length slope was divided into 43 sections (25m differences) which are CH0 to CH875 to be simulated. The rockfall trajectory analysis conducted based on Colorado Rockfall Simulation Program (CRSP) and Lump Mass Method. The CRSP and Lump Mass Method were developed based on equation of motion to estimate energy, velocity, and height of bouncing of rock.  The analysis shows that the maximum rolling distance for slope ranged from 56m to 440m from slope toe. The rock blocks from slope CH188, CH213, CH475, CH500, CH513, CH525, CH538, CH550, CH563, CH575, CH588, CH688, CH700, CH713, CH725, CH738, CH763, CH775, CH788, CH800, CH813, CH825 and CH838 were simulated to fall toward Kampung Sungai Ati.  

Figure 5: Example of rockfall run out analysis conducted by using Rocfall software
Figure 5: Example of rockfall run out analysis conducted by using Rocfall software

The hazard zones were determined based on the results of rock fall analysis and Guideline by JMG (2013). The hazard zones divided into three (3) zones which are high hazard zone, intermediate hazard zone and low hazard zone. Distance of high hazard zone, intermediate hazard zone and low hazard zone in entire study areas were ranging from 56 m to 440 m, 12 m to 473 m and 381 m to 566 m. The distance of high hazard zone is the maximum rolling distance. The distance of intermediate hazard zone was calculated by minus the 1.5 times of height of slope (1.5H) with maximum rolling distance of rock fall. The distance of low hazard zone is equal to the 1.5 times of height of slope, H. 

Figure 6: Hazard zones and slope stability distribution for Gunung Pondok, Padang Rengas, Perak
Figure 6: Hazard zones and slope stability distribution for Gunung Pondok, Padang Rengas, Perak

SUGGESTION AND RECOMMENDATION

The results of the analysis have been presented to the State’s Exco in 2016. The state together with the Perak Hanjong management are on negotiation to choose the best method to avoid harm to the people.  As for GMT, based on the results and analysis, the long-term best mitigation measure to reduce the risk from the hazard hill is to establish and demarcate a buffer zone around the hazard hill.   

CONCLUSION 

The hazard assessments of 49 slopes (875 m) using Slope Mass Rating (SMR) rock mass classification suggested that the probability of failure of slopes at study area ranging from 0.2 to 0.9. The total width of slope with probability of failure of 0.2, 0.4, 0.6 and 0.9 are 200.25 m, 337.25 m, 281.25 m and 56.25 m respectively. The stability of slopes varies from Completely Unstable to Stable. The rock fall analysis recommended that the maximum rolling distances for slope ranging from 56 m to 440 m from slope toe. The rock fall simulation results suggested that the distance of high hazard zone, intermediate hazard zone and low hazard zone in this study area were ranging from 56 m to 440 m, 12 m to 473 m and 381 m to 566 m. 

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ENGINEERING GEOLOGY ASSESSMENT FOR PROPOSED PERMANENT STABILIZATION FOR GRANITE ROCK SLOPE IN MALAYSIA

NATURE OF PROJECT: ENGINEERING GEOLOGY AND ROCK SLOPE STABILITY ASSESSMENT
DURATION: 4 MONTHS
DURATION: AUG 2018

BACKGROUND AND METHODOLOGY

Geomapping Technology Sdn. Bhd. undertook the assessment on engineering geological assessement and rock slope stability mapping at Bukit Lanjan, Selangor. The lithology of the cut slope consists of granitic rock mass with weathering Grade I to Grade III. Due to the nature of the outcrop, engineering geology assessments is conducted to obtain optimal engineering geological data for comprehensive analysis for rock slope stability. The engineering geological survey methods are: 

  • Discontinuity Survey: Scanline survey and Terrestrial Laser Scanning (TLS) 
  • Airborne survey using UAV/drone 
  • Kinematic analysis 
  • Rock Mass Rating (RMR) and Slope Mass Rating (SMR) 
  • Modified Geological Strength Index (GSI) 

RESULTS AND DISCUSSION 

Based on discontinuity mapping, multiple potential failures were identified using kinematic analysis which was represented potential instabilities on site. The demarcated potential failure is depicted as the major potential failure mode. Each major potential failure blocks were labeled with unique ID and analyzed with limit equilibrium method.  

Rock masses were assigned   RMR and SMR rating based on the parameters acquired from the mapping survey. The orientations of potential failure plane were used in readjustment factor in SMR analysis. Based on SMR classification, the slopes were identified as Class II (Stable), Class III (Partially Stable) and Class IV (Potentially Unstable).

Figure 1: Oblique aerial photograph showing identified potential instabilities and it is given ID.
Figure 1: Oblique aerial photograph showing identified potential instabilities and it is given ID.

The rock masses were also analysed using modified GSI method and the results shows good correlation with RMR (Bieniawski,1989). 

Figure 2: Results of TLS point cloud data processed in Coltop3D showing characterized discontinuity sets.
Figure 2: Results of TLS point cloud data processed in Coltop3D showing characterized discontinuity sets.

CONCLUSION 

Empirical method and rating systems such as kinematic analysis, Rock Mass Rating, Slope Mass Rating, and Geological Strength Index are very useful in determine the rock mass rating for mitigation works. However, limit equilibrium analysis will provide more information on slope stability in specific condition. 

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BOULDER MAPPING FOR ELEVATED HIGHWAY CONSTRUCTION IN GRANITE HILL AT AMPANG JAYA

NATURE OF PROJECT: GEOLOGICAL & GEOHAZARDS ASSESSMENT
CLIENT: PROJEK LINTASAN SUNGAI BESI – ULU KELANG SDN BHD
DURATION: DEC 2017 – MAR 2018

INTRODUCTION 

SUKE is a 24.4km, three-lane, dual-carriageway, elevated expressway running from Sri Petaling to Ulu Kelang. It has 14 interchanges and reaches out to over 60 residential areas as well as connects to major highways and roads in Kuala Lumpur. SUKE will serve as a viable alternative to MRR2 highway by minimizing traffic congestion in Cheras, Pandan Indah, and Ampang, as a direct link for a new greater growth city such as Kajang, Segambut, and Kepong and as an effective and high capacity traffic dispersal scheme for eastern Klang Valley areas. At package CB1 (B7 & B8), the proposed highway alignment is in close distance with the residential houses of Taman Saga. Boulder fall hazard is one of the geological problems encountered at this location.  

Figure 1: The highway alignment in close distance with residential houses.
Figure 1: The highway alignment in close distance with residential houses.

BOULDER MAPPING 

Boulder mapping was conducted on hilly terrain with several streams flow down the slope towards depression areas close to Taman Saga. The boulder mapping was conducted to map the location and condition of the boulders and recommend suitable remedial type. The mapping methodology was adopted from the suggestion of Au and Chan (1991) and  engineering judgment based on available records. Besides, the field observation is important to study the hazard posed by the boulders.  Six (6) criteria were considered for this boulder mapping which are; i) Boulder location, ii) Embedded depth, iii) Boulder shape, iv) Boulder size, v) Local slope angle, and vi) Vegetation density.  

RESULTS 

There are two (2) areas of boulders accumulation exist in the project site which are; i) The boulders on the slope face near to Taman Saga: which have the potential of boulders fall as its located on the slope steeper than 35°. In fact, there also incidents of boulders fall during construction due to excavation works. ii) The boulders located along the stream channels in the forest reserve which prone to debris flow hazards. 

Figure 2: Distribution of boulders on the slope face and along stream channel
Figure 2: Distribution of boulders on the slope face and along stream channel

RECOMMENDATIONS 

Conceptual recommendations were suggested at this particular area such as stabilization/scaling (boulders on a slope) and installation of flexible protection net (boulders along the streams) to mitigate this issue as shown in Figure 3. Hence, the boulder mapping execution is very crucial at any locations that face the same problems with Taman Saga, especially on granitic rocks area. 

Figure 3: Suggested recommendations for the boulders hazard
Figure 3: Suggested recommendations for the boulders hazard
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GROUNDWATER MODELING IN SG MUDA BASIN, KEDAH

NATURE OF PROJECT: BASIN SCALE MODELLING FOR GROUNDWATER RESOURCE DEVELOPMENT
CLIENT: JABATAN MINERAL DAN GEOSAINS MALAYSIA (JMG) KEDAH / PERLIS / PULAU PINANG
DURATION: JUNE – NOV 2018

INTRODUCTION 

Muda Basin in Kedah and its neighboring states of Pulau Pinang as well as a part of the state of Perlis are faced with the problem of water shortage which persist year in year out. Jabatan Mineral Dan Geosains Malaysia (JMG) is faced with the task to resolve the problem.  Systematical evaluation of the groundwater potentials in the Basin is carried out by JMG. For this purpose, JMG Kedah/Perlis/Pulau Pinang awarded the groundwater modelling project to Geomapping Technology (GMT) Sdn. Bhd. to develop a groundwater flow model for the aquifer at Sungai Muda Basin (4,210 km2). The primary objective is to estimate the groundwater reserve and maximum sustainable extractions from the aquifer to support technical decision for planning and groundwater resource development of the Basin.

METHODOLOGY 

The approach used in this study include: 

  • Desktop review and previous data gathering 
  • Data processing and management using state-of-the-art software e.g. ArcGIS, Rockworks, Surfer and Aquifer Test to aid groundwater development.
  • Numerical Modelling  

 The three-dimensional numerical code, Modular finite-differential flow (MODFLOW) by U.S. Geological Survey was used for finite differential solutions for the reserve estimates, ZONE BUDGET was used to assess the availability of groundwater in six (6) zones and sub-catchment. Data were integrated on the platform of Visual MODFLOW flex software. 

CONCEPTUAL MODEL 

Three (3) hydrostratigraphic unit were considered for Muda Basin. This comprises of two aquifer system: (i) upper aquifer and (ii) fractured bedrock aquifer. The layers are: one unconfined layer at the top of the model (Layer 1:Quarternary Alluvium), one semi-confined layer (convertible from confined to unconfined) that defines the main Muda Basin aquifer (Layer 2:coarse sands and weathered rocks) and lastly one confined, underlying fractured bedrock aquifer (Layer 3) from Semanggol (sandstone/siltstone, shale), Mahang (shale, sandstone) Baling (shale, siltstone, sandstone , limestone) and Granite Formations.  

Figure 1: Conceptual site model of Muda River Basin Kedah overlain with photo map of the study area
Figure 1: Conceptual site model of Muda River Basin Kedah overlain with photo map of the study area

RESULT & DISCUSSION 

(i) The model performed well with standard error of estimate at 0.29 m, RMSE (9.8 m) and correlation coefficient of 0.92. The regional trend of groundwater is north-southwest towards the coast (Strait of Melaka). (ii) The total flow of groundwater through the Muda Basin is ≈14.1 million m3/day. Groundwater storage (∆s) is ≈11.7 million m3/day (11,766,812.45 m3/day). The Basin is recharge at 180 mm/yr (7.2 % of average annual rainfall of 2477.78mm/yr).  The bulk of recharge comes from rainfall (2,098,631.00 m3/day).  

CONCLUSION 

For groundwater development to be sustainable in the basin, maximum sustainable extraction (safe yield) for Muda River Basin is by making all abstraction less than 50 % of natural recharge. 

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RESERVE ASSESSMENT STUDY OF UNDERGROUND WATER RESOURCES IN SG KELANG BASIN, SELANGOR

NATURE OF PROJECT: BASIN SCALE MODELLING FOR GROUNDWATER RESOURCE DEVELOPMENT
CLIENT: JABATAN MINERAL DAN GEOSAINS MALAYSIA (JMG) SELANGOR / WILAYAH PERSEKUTUAN
DURATION: JUNE – NOV 2018

INTRODUCTION 

Selangor State in Malaysia have reached a decision that a quick fix to the water deficit  is to develop groundwater as supplementary raw water supply for various users. Groundwater modelling is considered the most valuable and powerful management tool that is useful to effectively perform the complex task. For the basin scale groundwater modelling, Jabatan Mineral Dan Geosains (JMG) Selangor, Malaysia awarded the groundwater modelling project to Geomapping Technology (GMT) Sdn. Bhd. to develop a regional groundwater flow model for the aquifer at Sungai Kelang Basin (1,288 km2). The primary objective is to estimate the groundwater reserve and maximum sustainable extractions from the aquifer to support technical decision for planning and groundwater resource development of the Basin.  

METHODOLOGY 

The approach used in this study include: 

  • Desktop review and previous data gathering 
  • Data processing and management  
  • Field investigation for new data capture
  • Numerical Modelling  

 Modular finite-differential flow (MODFLOW) by U.S. Geological Survey was used for finite differential solutions for the reserve estimates, MODPATH (modular finite differential path lines) and ZONE BUDGET was used to assess the availability of groundwater in five (5) zones and sub-catchment areas.  

REGIONAL CONCEPTUAL MODEL OF KELANG BASIN 

Kelang Basin was modelled as three (3) main hydrostratigraphic unit and comprise of two aquifer system (upper aquifer and fractured bedrock aquifer). The layers comprise of one unconfined layer (Layer 1), one confined upper aquifer (Layer 2) and semi-confined fractured bedrock aquifer (Layer 3).  Layer 1 is Quaternary Alluvium/completely weathered soil (sandy clay /sandy silt). Average thickness is estimated to be 12.3 m. Layer 2 (Alluvium clayey sand/silty sand) is the upper aquifer (10.7 m). Layer 3 is fractured bedrock and comprises of relatively less permeable Kuala Lumpur Limestone Formation, Kenny Hill Formation (mainly sandstone) and Hawthornden Schist Formation (schist, and phyllite). Assumed thickness for the fractured bedrock is 250 m. 

Figure 1: Conceptual site model of Kelang River Basin
Figure 1: Conceptual site model of Kelang River Basin

RESULT & DISCUSSION 

(i) The model calibration performed well: standard error of estimate is 0.47 m, RMSE: 9.56 m and correlation coefficient: 0.78. The regional movement o of groundwater is northwest-southwest towards the west coast (Strait of Melaka). (ii) Total inflow of fresh groundwater to the Basin is ≈6.1 million m3/day (6,132,655 m3/day). Groundwater reserve (∆s) is 589,422.25 m3/day). The Basin is recharged at 260 mm/yr (10.5 % of average annual rainfall of 2465mm/yr).  The bulk of recharge to the aquifer comes from rainfall (918,899.06 m3/day).  

CONCLUSION 

For groundwater development to be sustainable, maximum sustainable extraction for the Basin is recommended at 50 % of natural recharge. 

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NUMERICAL GROUNDWATER FLOW AND SOLUTE TRANSPORT MODELLING AT FELDA BUKIT GOH, PAHANG

NATURE OF PROJECT: GROUNDWATER FLOW & TRANSPORT MODELLING TO ASSESS THE HYDROGEOCHEMICAL RESPONSE OF ENGINEERED BUFFER (CONDISOIL-BM) IN GROUNDWATER
CLIENT: INDUSTRY CENTRE OF EXCELLENCE (UNIVERSITY MALAYSIA PAHANG)
DURATION: OCT 2017 – FEB 2018

INTRODUCTION 

Groundwater flow and solute transport modelling was conducted on site at FELDA Bukit Goh. The model was used to support an extensive investigation on the applicability of a residue formulation (Condisoil-BM) to be used as an alternative backfill and engineering buffer/soil conditioner for agriculture purposes. There are two main objectives for the groundwater modelling: (i) to provide information on groundwater flow characteristics at the site, (ii) to model the rate and transport of contaminants [Calcium (Ca) and Yttrium (Y)] that may leach from Condisoil-BM. 

Figure 1: Aerial photo (Orthophoto) of study area. Red arrow indicates the excavated area for the emplacement of Condisoil -BM.
Figure 1: Aerial photo (Orthophoto) of study area. Red arrow indicates the excavated area for the emplacement of Condisoil -BM.

MODELLING OF THE SITE

Bukit Goh site is considered as hydrostratigraphic unit comprising one aquifer. Layer 1 (sandy clayey SILT/ silty CLAY) is the top layer. Average thickness is 9m. This is the layer of emplaced Condisoil -BM and the layer assumed to be the unit providing rainfall recharge to the underlying aquifer at Layer 2. The area of emplaced Condisoil-BM has dimensions: 25 x 25m, depth is from 0- 4.85 m bgl. Layer 2 (silty SAND) is the aquifer at the Bukit Goh site and 9m thick.  

Figure 2: Four main hydrostratigraphic unit at Bukit Goh with one aquifer (Layer 2) and Condisoil-BM at the Layer 1 upper section
Figure 2: Four main hydrostratigraphic unit at Bukit Goh with one aquifer (Layer 2) and Condisoil-BM at the Layer 1 upper section

RESULT & DISCUSSION 

The flow at the site generally trend northwest – southeast towards the direction of a local river located outside the boundary of the study area.

Figure 3: simulated groundwater head contours in the Layer 1 (sandy clayey SILT/ silty CLAY, Scenario II -after Condisoil-BM emplacement)
Figure 3: simulated groundwater head contours in the Layer 1 (sandy clayey SILT/ silty CLAY, Scenario II -after Condisoil-BM emplacement)
Figure 4: Transport of Ca contained within the Condisoil-BM location (Layer 1) after 7300 days (20 years).
Figure 4: Transport of Ca contained within the Condisoil-BM location (Layer 1) after 7300 days (20 years).

CONCLUSION 

Ca will reach the aquifer after 20 years (7300 days) under an assumption of zero sorption). The emplaced Condisoil–BM is relatively impermeable and able to restrain the movement of contaminants from reaching the groundwater zones. 

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NUMERICAL GROUNDWATER FLOW AND SOLUTE TRANSPORT MODELLING FOR THE PROPOSED ONSITE SECURED LANDFILL

NATURE OF PROJECT: GROUNDWATER FLOW & TRANSPORT MODELLING FOR LANDFILL DESIGN / ENVIRONMENT IMPACT ASSESSMENT
CLIENT: LYNAS MALAYSIA SDN BHD
DURATION: FEB – MAR 2019

BACKGROUND AND METHODOLOGY 

Numerical Groundwater flow and solute transport modelling was used to establish the (i) groundwater flow characteristics, (ii) migration of contaminants (Pb, Cr, Zn, Ba and Hg) from the proposed onsite secured Landfill (Prescribed Premise) for Neutralized Underflow (NUF) solids at  Kuantan Malaysia.  

(i) Numerical Modelling Approach – The study applies the advanced method of using computer modelling technique, numerical code Modular finite-differential flow (MODFLOW) for assessment. The transient-state model was used to simulate a worst-case scenario under various assumptions: (i) secured landfills at the site are unlined (non -engineered type), (ii) contaminant are non-reactive i.e. adsorption process is negligible and contaminants are expected to migrate at maximum concentration to groundwater. 

(ii) Model Development – Six hydrostratigraphic layers were modelled comprising of two aquifer systems: 

Table 1: Hydrostratigraphic layers of the area.
Table 1: Hydrostratigraphic layers of the area.

RESULT & DISCUSSION 

Figure 1: Six (6) layers of hydrostratigraphic unit at LAMP site that was used in the model
Figure 1: Six (6) layers of hydrostratigraphic unit at LAMP site that was used in the model

(i) Groundwater movement is northeast –southwest, and north-south towards the earthen waste water retention pond at the site. The flow is outwardly discharging to the South China Sea at the southern part of LAMP site. 

Figure 2: groundwater movement towards the waste water retention pond at the site. The pond is hydraulically connected with the aquifers..
Figure 2: groundwater movement towards the waste water retention pond at the site. The pond is hydraulically connected with the aquifers..

(ii) Contaminant (Pb, Cr, Ba, Hg) will reach the upper aquifer after 3650 days (10 yrs.) of migration and Zn will reach after 730 days (2yrs) under assumptions of unlined landfill (no liner systems).  

Figure 3: Pb migration after 10950 days (30 years) in (Model 2).
Figure 3: Pb migration after 10950 days (30 years) in (Model 2).

CONCLUSION 

The model demonstrates that there is minimal negative impact associated with the landfill design to the environment and surrounding rivers due to double liners, moderate permeability of the aquifer and clay layer absorptive properties to retard the contaminants. 

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SHORT PILES AND ARBITRATION CASE OVER KARSTIC FORMATION

NATURE OF PROJECT: INDEPENDENT TECHNICAL REVIEW REPORT OF PROPOSED MIXED DEVELOPMENT OF LAND
CLIENT: EK INTEGRATED CONSTRUCTION SDN BHD
DURATION: MAY 2018 – CURRENT

INTRODUCTION

Independent technical review report was prepared by Geomapping Technology Sdn. Bhd. for the used of EK Integrated Construction Sdn. Bhd. to review the foundation design and construction of proposed mixed development of residential areas located at Kepong, Selangor.  

Dispute in construction is triggered due to technical disagreement of pile foundation that shows subsequent settlement issues on post-construction phase. 

The preparation of the technical report was produced based on the existing documents received from the Client. 

ARBITRATION ACTS IN MALAYSIA 

Arbitration Act 1952 had been governed for a long period of time until it is replaced by the Arbitration Act 2005 which enforced on 15th March, 2006. Latest Arbitration Act recognised the requirement of minute court interference and the need for finality of the dispute resolution. 

In addition, arbitration is regarded the ultimate mechanism to resolve dispute accompany by some attractive features such as confidentiality, fast, elasticity and selection of the arbitrator. 

CONSTRUCTION ISSUES 

The settlement of foundation structures at the study area may occur due to the formation of cavities beneath the soil layers. The placement of the pile structure above the cavity parts may induce instability of the pile foundation. The strength of the roof segments in cavities may not able to withstand the overburden loads from the soils and foundation structures.  

Figure 1: Placing of pile structure on cavity.
Figure 1: Placing of pile structure on cavity.

Inclined bedrock surfaces may lead to the pile foundation failure. Distortion, bending, and breakage are several examples which related to the driving of pile into karstic bedrock surface. The damage of the pile tip and poor placing of the pile tips into the bearing layer also may occur during piling works due to uneven substratum surface. 

Figure 2: Formation of karstic bedrock surface in Kuala Lumpur area (after Yeap, 1985).
Figure 2: Formation of karstic bedrock surface in Kuala Lumpur area (after Yeap, 1985).

CONCLUSION 

The design and construction of pile foundation in limestone formation pose great challenges which may affect the integrity of the pile structure. Proper site investigation procedure and good geological and geotechnical interpretation must be implemented into practice to avoid post-construction failures. 

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CONSTRUCTION OF ENGINEERED SANITARY LANDFILL IN GEBENG INDUSTRIAL AREA, PAHANG

NATURE OF PROJECT: CONTRUCTION OF SANITARY LANDFILL
DURATION: NOV 2018 – MAY 2019

BACKGROUND

Construction of engineered sanitary landfill was designed and supervised by Geomapping Technology Team. Environmental impact of leachate and hazardous materials can be reduced exponentially with proper engineered sanitary landfill. The sanitary landfill was required to store and contain the Water Leached Purification residues. 

CONSTRUCTION OF STORAGE FACILITY 

Embankment Construction

The perimeter embankment was constructed at RL 8 having height of 3 metres. The gradient of the perimeter embankment is 1V:2H. The purpose of this structure is to contain the residue materials. Construction works utilized the earthfill materials mostly collected from local borrow sources.  

Figure 1: Clearing and grubbing process in action. Removing plants and flattening the ground level.
Figure 1: Clearing and grubbing process in action. Removing plants and flattening the ground level.

Under Liner Leak Detection (ULLD) System

The ULLD system was constructed purposely to detect seepage through the liner system. Basin areas were contoured to ensure a minimal fall of 1V:250H towards the ULLD pit. 

Figure 2: Geofabric arrangement for Under Liner Leak Detection (ULLD) system.
Figure 2: Geofabric arrangement for Under Liner Leak Detection (ULLD) system.

Leachate Collection System

Leachate collection system is a network of perforated HDPE pipes arranged in a herring bone pattern at 1V:250H gradient, purposely to collect and remove leachate material out of the landfill cell. 

Figure 3: Leachate collection system.
Figure 3: Leachate collection system.

CONCLUSION 

Good construction planning must be implemented into practice to make sure the sustainability of the sanitary landfill. 

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LiDAR-DERIVED GEOHAZARD ASSESSMENT FOR THE SUKE HIGHWAY, ULU KELANG, SELANGOR

NATURE OF PROJECT: GEOLOGICAL & GEOHAZARDS ASSESSMENT
CLIENT: PROJEK LINTASAN SUNGAI BESI – ULU KELANG SDN BHD
DURATION: MARCH 2019 – JULY 2019

INTRODUCTION

SUKE is a 24.4km, three-lane, dual-carriageway, elevated expressway running from Sri Petaling to Ulu Kelang. It has 14 interchanges and reaches out to over 60 residential areas as well as connects to major highways and roads in Kuala Lumpur. Initial assessment on 2018 proved that there is a need to conduct a detailed study on the landslide-prone area along the designated package due to the proximity to the residential houses as well as considering the potential hazard to the highway itself. Thus, GMT has conducted LiDAR survey to detect potential landslide additionally sources from outside the ROW of the highway.  

LiDAR data acquisition was done along the designated package of the SUKE highway stretch on 11th April 2019. Several products from LiDAR were generated such as Georeferenced Orthomosaic model, classified point cloud, Digital Surface Model (DSM), Digital Terrain Model (DTM) and Contour Map. Interpretations were made based on aerial imagery (orthomosaic) and LiDAR DTM data. Several factors were identified based on the published methodology, with conceptual model generated for geohazards within the designated study area.  

Guidelines for Natural Terrain Hazard Studies by Ho and Roberts (2016) were used to analyzed the parameter such as i) Catchment characteristics, ii) Surface Geology, iii) Bedrock Geology, iv) Landslide Scars and Slope Features, v) Anthropogenic Features, vi) Erosion and vii) land use.  

RESULT 

The assessments are focused on three main type of geohazards, namely landslide, debris flow and rock fall.  

Recent landslides, dormant landslides, flow-path of potential debris flow as well as the potential rock fall area are identified. From the assessment, there are 19 locations identified to potentially of geohazard occurrences where six (6) locations for landslides, nine (9) locations for debris flow and four (4) locations for rock fall. Figure 1 shows some of the identified geohazard locations that are tabulated in the Geohazard Risk Register Map. Apart from the assessment, proposed mitigation measure also suggested to overcome the potential problem.  

Figure 1: Some of the identified geohazard at the designated package of the highway. Potential landslide is labelled as L, debris flow as DF while rockfall as RF.
Figure 1: Some of the identified geohazard at the designated package of the highway. Potential landslide is labelled as L, debris flow as DF while rockfall as RF.

CONCLUSION 

LiDAR data is a useful method in geohazard study. The data that capture wide area in limited time useful especially for any project area that are inaccessible and have time constraint. However, there are also some limitation of the technology especially for the area with very thick vegetation cover and forest canopy. The interpretation of geohazard shall be conducted by the Professional Geologist (P.Geol) or geologist under direct supervision of the Professional Geologist.  

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