The effect of tree induced suction on slope stability analysis

Nowadays, many problems regarding slope failure happened due to cutting down of vegetation. The existence of tree on top of slope is very important to increase soil slope stability. This study explore the influence of active root tree zone (Alstonia Angustiloba) located on top of a slope to reduce soil moisture content thus increase the shear strength of soil slope. Soil matric suction generated at the vicinity of the slope due to tree water uptake is the main focus of this study since it will influence the factor of safety (FOS) of slope. This research employed several approaches i.e field monitoring work for soil suction and rainfall collection, laboratory works for soil classification and determining the shear strength parameters of the soil, subsurface investigation using electrical resistivity imaging (ERI), digital mapping using unmanned aerial vehicle (UAV) and verification of actual soil suction pattern with numerical modelling. Field monitoring works were carried out to obtain soil suction data at the selected slope with two conditions (without and with tree on top of the slope). The unsaturated shear strength behaviour under different stress level was investigated, by conducting consolidated isotropic undrained (CIU) test by replicating the actual matric suction monitored at the study area. From this suction pattern, it was proven that the majority of suction changes were greater at the proximity of the tree trunk (1.1 m) and at a shallow depth of 0.25 m. In addition, Electrical Resistivity Imaging (ERI) was conducted on two layouts (horizontal and vertical) of the slope to obtain the subsurface images of the slope. This ERI survey applies two protocols known as Wenner protocol and Schlumberger protocol. These images from ERI were compared to unsaturated soil suction contour generated using GiD software. This study also implement modern methods for soil slope mapping by using unmanned aerial vehicle (UAV). The findings also applied the safety values (FOS) on 18th February 2018 and 22nd February 2018 into the map to study the daily stability values of the slope and considered as the main novelty of this study. Finally, numerical simulation modelling was applied based on the laboratory results to obtain most appropriate condition to replicate tree water uptake within soil slope during dry period. The factor of safety (FOS) of soil slope in 19th February 2018 with tree on top of it reached up to 53 % higher compare to slope without tree. From the results of comparison between suction contour and ERI contour, soil suction contour proved to be more suitable in term of stability analysis, while the ERI contour is more suitable to detect underlying materials underneath the soil based on the ability of materials to resist or allow electric current flow. This study verified the finding from ERI survey with the soil properties of Pahang Matriculation College. ERI prove the existence of clay in the soil which verified the high clay contents (22.8 %) in the soil itself. Finally, an acceptable agreement has been achieved between simulation of numerical modelling and actual suction collected from field monitoring work with a small difference of 5 % only. This research proved high influenced of single tree on top of soil slope to increase soil slope stability by decreasing the existence moisture in the soil itself

The Application of Unmanned Aerial Vehicle (UAV) For Slope Mapping at Gambang Damai Residents, Pahang: A Case Study

In this paper, the work of slope mapping using unmanned aerial vehicle (UAV) with its perimeter, area and volume of certain selected areas at Perumahan Taman Gambang Damai in Kuantan Pahang are discussed. Previous work of slope mapping using traditional survey equipment considered as time consuming and very challenging especially in hilly regions. This study also focused on determining the potential slope hazard based on slope angle. Modern UAV able to take high quality image which essential for the effectiveness and nature of normal mapping output such as Digital Elevation Model (DEM) and Digital Orthophoto. These photos captured by the UAV will later exported to Agisoft to generate full map of study area. With the help of Global Mapper, the measurement such as perimeter, area and volume of selected study areas can be determined easily and considered as the main interest in this study. Based on the results of the two slopes (slope A and slope B), slope B give a bigger volume which is 1469.7 m3 compare to slope A which is 1382.9 m3. The enclosed area for slope A is 1634.3 m2 which is bigger compare to slope B which is 766.86 m2. Besides, the perimeter of slope A is 162.28 m which is bigger compare to slope B which is 159.45 m. In addition, another outcome of this study is, this modern method of mapping helps researchers and engineers to study the possibility of slope hazard based on their respective slope angle. From the results, the angle for slope A is 47.35⁰ while the angle for slope B is 54.75⁰. Both of the slopes considered as very steep slope. In conclusion, modern technology of UAV proves to be very effective for mapping in geotechnical engineering. Slope mapping using multi-rotor UAV help researchers and engineers to obtain slope measurement within short period of time compare to previous traditional method

The Application of Unmanned Aerial Vehicle (UAV) For Slope Mapping at Gambang Damai Residents, Pahang: A Case Study

In this paper, the work of slope mapping using unmanned aerial vehicle (UAV) with its perimeter, area and volume of certain selected areas at Perumahan Taman Gambang Damai in Kuantan Pahang are discussed. Previous work of slope mapping using traditional survey equipment considered as time consuming and very challenging especially in hilly regions. This study also focused on determining the potential slope hazard based on slope angle. Modern UAV able to take high quality image which essential for the effectiveness and nature of normal mapping output such as Digital Elevation Model (DEM) and Digital Orthophoto. These photos captured by the UAV will later exported to Agisoft to generate full map of study area. With the help of Global Mapper, the measurement such as perimeter, area and volume of selected study areas can be determined easily and considered as the main interest in this study. Based on the results of the two slopes (slope A and slope B), slope B give a bigger volume which is 1469.7 m3 compare to slope A which is 1382.9 m3. The enclosed area for slope A is 1634.3 m2 which is bigger compare to slope B which is 766.86 m2. Besides, the perimeter of slope A is 162.28 m which is bigger compare to slope B which is 159.45 m. In addition, another outcome of this study is, this modern method of mapping helps researchers and engineers to study the possibility of slope hazard based on their respective slope angle. From the results, the angle for slope A is 47.35⁰ while the angle for slope B is 54.75⁰. Both of the slopes considered as very steep slope. In conclusion, modern technology of UAV proves to be very effective for mapping in geotechnical engineering. Slope mapping using multi-rotor UAV help researchers and engineers to obtain slope measurement within short period of time compare to previous traditional method

Forensic assessment on landfills leachate through electrical resistivity imaging at Simpang Renggam in Johor, Malaysia

From years to years, the usage of electrical resistivity imaging (ERI) method dominated by geophysicist has increased tremendously in geotechnical engineering application owing to the efficiency and effectiveness of the method in term of time, cost and also data coverage. The forensic assessment performed with respect to the particular reference to ERI in assessing the landfills leachate at Simpang Renggam, Malaysia. There were two lines of ERI performed at the study area by using ABEM Terrameter LS 2 set of equipment based on Schlumberger array. Furthermore, the analysis made based on the electrical resistivity anomaly managed to detect the presence of chemical contaminants in the soil with particular reference to the chemicals resistivity values which was associated to low resistivity anomaly. Besides, the heterogeneous of the subsurface material presented in the paper by using integrated ERI analysis enabled forensic assessment of the leachate. The leachate from the landfills was believed to occur owing to the failure of the systems in accommodating and treating the waste which became worst with the present of heavy rainfall. In retrospect, the ERI result was applicable to be adopted in detecting the leachate and thus can assist the authority in taking immediate measure to prevent the frequent water disruptions at the study area

Urban landfills investigation for leachate assessment using electrical resistivity imaging in Johor, Malaysia

The use of the electrical resistivity imaging (ERI) approach has expanded dramatically in engineering applications over the years due to the efficiency of the technique in terms of time, expense, and data coverage. The assessment was carried out using ERI to assess the landfill leachate's pollution level at Simpang Renggam, Johor, Malaysia. The ERI survey was carried out in the research region, utilizing the ABEM Terrameter LS 2 equipment using the Schlumberger electrode configuration. Besides, seven (7) parameters of leachate characterization such as Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5), Suspended Solid (SS), Power of Hydrogen (pH), Ammonia Hydrogen (NH3-N), Turbidity and Biodegradability Ratio (BOD5/COD) were also performed to identify and evaluate the current leachate condition of the landfill. Furthermore, the study, which involves the measurement of the apparent resistivity of the subsurface materials were able to determine the existence of chemical pollutants in the soil at 1.5 m to 4.0 m depth, with special reference to the chemically apparent resistivity linked with the low resistivity anomalies of 1 – 10 Ωm. Based on the investigations conducted, the physiochemical and microbial analysis of the Simpang Renggam leachate site was found to be 1633 mg/L (Chemical Oxygen Demand), 137.41 mg/L (Biological Oxygen Demand), 359.8 mg/L (Suspended Solid), 7.61 (Power of Hydrogen), 385.29 (Ammonia Hydrogen), 117.65 (Turbidity) and 0.07 (Biodegradability Ratio) which shows that all of the parameter's value exceeded the value as stated in the local standard which is Environmental Quality Act (1974) except for the pH value which is within the range value as stated in the standard. The leachate from dumps was thought to arise due to system failures in accepting and managing trash, which was exacerbated by the recent high rains. In hindsight, the ERI result was practical for identifying leachate and, therefore, can benefit the authorities in immediate action to halt the extensive water disturbance at the research region

Influence of Alstonia Angustiloba tree water uptake on slope stability: A case study at the unsaturated slope, Pahang, Malaysia

Although previous research has significantly enhanced our understanding of problematic and unsaturated soil behaviour and interaction with structures, there is still an urgent need to address the difficult scenarios that are met with problematic and unsaturated soils. This study examines the effects of tree water uptake at different depths and distances on the improvement of induced water uptakes caused by transpiration via mature Alstonia Angustiloba tree. This study is performed to examine the tree water uptake profile in a vegetated slope with the existence of mature Alstonia Angustiloba tree at the top and the stability of the slope during various precipitation penetration events by which the data of the tree water uptake produced within this section of the slope is recorded and implemented to evaluate the factor of safety (FOS). Slope stability analysis is further conducted to explore how plant transpiration affects slope stability. The results indicate that higher tree water uptake lead to the greatest increase of FOS of the slope up to 53% (from 2.17 to 4.57). The highest tree water uptake recorded was at the slope station with Alstonia Angustiloba tree with a depth of 0.25 m and a distance of 1.1 m from the tree. The tree water uptake utilized in this study can contribute to a carbon-free and eco-friendly approach which can be implemented globally to prevent slope failures

The Application of Unmanned Aerial Vehicles (UAV) for Slope Mapping with the Determination of Potential Slope Hazards

In our modern world, the application of small unmanned aerial vehicles (UAV) for monitoring work or slope mapping expanded and is widely used by people in the construction field and researchers. Slope mapping can be considered challenging when using traditional surveying methods since most slopes especially in forest regions are high and considered risky if monitored by human themselves. Other than that, mapping by using UAV need a lower number of manpower to operate the device itself which is more than enough to be conducted by a single person only. This paper discusses the applications of unmanned aerial vehicles for mapping and also its important parameters including perimeter, area and also volume of certain selected area. With the development of modern technology, the utilization of UAV to gather data for geological mapping is becoming easier as it is quick, reliable, precise, cost-effective and also easy to operate. High imagery quality and high-resolution images are essential for the effectiveness and nature of normal mapping output such as digital elevation model (DEM) and also orthoimages. With the help of established software, the parameters of three selected study areas (stockpile, slope A and slope B) can be determined easily which can be considered as one of the main interest in this study. In addition to that, the horizontal and vertical cross section of every selected area can be obtained which help to determine the highest and lowest point of each area. From this cross section, the slope path profile can be determined. Other than that, from this path profile, the potential slope hazard will be determined based on the slope angle (slope classes) as suggested by the United States Department of Agriculture (USDA). Overall, the application of unmanned aerial vehicles for photogrammetry together with slope mapping and slope hazard monitoring can be considered as a reliable modern technology which ease the work with proper assurance of analysis due to its advancement and powerful technology. This modern surveying device helps workers and researchers to simplify and fasten their work

Compressibility Behaviour On Carbonation of Ground Granulated Blast Furnace Slag (GGBS) Treated Kaolin

With the growing worry over pollution in the environment, the necessity to comprehend this phenomenon has multiplied. Not only that, the economic gain made in the last decade, along with the fast growth of the world population, has come at a huge environmental cost. One of the never-ending issues is carbon dioxide emission and notably, the construction sector is no exception to mean to contribute through many development activities. Therefore, this study focuses on the compressibility behaviour of Ground Granulated Blast Furnace Slag (GGBS) treated kaolin clay due to carbonation. This study discusses the effect of carbonation on GGBS-treated kaolin as an effort to use sustainable materials which able to improve the geotechnical properties of soil and safe to say, help to reduce the emission of CO2. Testing program via one-dimensional consolidation test found that the compressibility characteristics improved as increased the GGBS content. Overall, the results illustrate that higher GGBS content and longer curing period gives lower compressibility characteristic. It was also found that the carbonated kaolin sample further improve the compressibility characteristics as compared to ambient condition of treated kaolin sample. In conclusion, GGBS can improve the compressibility characteristic of kaolin with carbonation consideration

Exploration of Method for Slope Stabilization Influenced by Unsaturated Soil

This study will lead to the analysis of unsaturated soil using Bishop’s Simplified method which is one method to analyze slope stability in method of slices. Bishop’s original formula of saturated soil was modified by adding the element of matric suction, ( ) a w together with unsaturated friction angle,b which is applicable for the analysis of unsaturated soil. In this study, 40 kPa of matric suctions was applied in the analysis for both Bishop and Fellenius methods. From the analysis, the results indicate that the factor of safety (FOS) value of Bishop’s Simplified method was 4.41 % higher than Fellenius’s method for 40 kPa suction, as the soil is in unsaturated condition. The reason for the relative accuracy of Bishop’s Simplified method is that in considering only the vertical equilibrium of any slice, there is no need to account for the horizontal components of the inter-slice forces

Exploration of Methods for Slope Stabilization Influence by Unsaturated Soil

This study will lead to the analysis of unsaturated soil using Bishop’s Simplified method which is one method to analyse slope stability in method of slices. In this study, the original formula for Bishop’s Simplified method of saturated soil were modified by adding the element of matric suction, together with unsaturated friction angle, which was applicable for the analysis of unsaturated soil. In this study, 0 kPa and 20 kPa of matric suctions were applied in the analysis for both methods. From the analysis, the result indicates that the factor of safety (FOS) value of Bishop’s Simplified method was 8.82 % higher than Fellenius’s method for 0 kPa suction, which means that the soil is in saturated condition. For 20 kPa of suction, the FOS of Bishop (1955) was 6.84 % higher than Fellenius (1936). It can be concluded that, the reason for the relative accuracy of the Bishop’s Simplified method is that in considering only the vertical equilibrium of any slice, there is no need to account for the horizontal components of the interslice forces