Mapping on slope seepage problem using Electrical Resistivity Imaging (ERI)

The stability of slope may influenced by several factors such as its geomaterial properties, geometry and environmental factors. Problematic slope due to seepage phenomenon will influenced the slope strength thus promoting to its failure. In the past, slope seepage mapping suffer from several limitation due to cost, time and data coverage. Conventional engineering tools to detect or mapped the seepage on slope experienced those problems involving large and high elevation of slope design. As a result, this study introduced geophysical tools for slope seepage mapping based on electrical resistivity method. Two spread lines of electrical resistivity imaging were performed on the slope crest using ABEM SAS 4000 equipment. Data acquisition configuration was based on long and short arrangement, schlumberger array and 2.5 m of equal electrode spacing interval. Raw data obtained from data acquisition was analyzed using RES2DINV software. Both of the resistivity results show that the slope studied consists of three different anomalies representing top soil (200 – 1000 Ωm), perched water (10 – 100 Ωm) and hard/dry layer (> 200 Ωm). It was found that seepage problem on slope studied was derived from perched water zones with electrical resistivity value of 10 – 100 Ωm. Perched water zone has been detected at 6 m depth from the ground level with varying thickness at 5 m and over. Resistivity results have shown some good similarity output with reference to borehole data, geological map and site observation thus verified the resistivity results interpretation. Hence, this study has shown that the electrical resistivity imaging was applicable in slope seepage mapping which consider efficient in term of cost, time, data coverage and sustainability

Integral Analysis of Seismic Refraction and Ambient Vibration Survey for Subsurface Profile Evaluation

Geotechnical site investigation as known as subsurface profile evaluation is the process of subsurface layer characteristics determination which finally used for design and construction phase. Traditionally, site investigation was performed using drilling technique thus suffers from several limitation due to cost, time, data coverage and sustainability. In order to overcome those problems, this study adopted surface techniques using seismic refraction and ambient vibration method for subsurface profile depth evaluation. Seismic refraction data acquisition and processing was performed using ABEM Terraloc and OPTIM software respectively. Meanwhile ambient vibration data acquisition and processing was performed using CityShark II, Lennartz and GEOPSY software respectively. It was found that studied area consist of two layers representing overburden and bedrock geomaterials based on p-wave velocity value (vp = 300 – 2500 m/s and vp > 2500 m/s) and natural frequency value (Fo = 3.37 – 3.90 Hz) analyzed. Further analysis found that both methods show some good similarity in term of depth and thickness with percentage accuracy at 60 – 97%. Consequently, this study has demonstrated that the application of seismic refractin and ambient vibration method was applicable in subsurface profile depth and thickness estimation. Moreover, surface technique which consider as non-destructive method adopted in this study was able to compliment conventional drilling method in term of cost, time, data coverage and environmental sustainaibility

Integral application of electrical resistivity tomography, geochemistry and borehole data in groundwater seepage assessment

Electrical resistivity tomography (ERT) has increasingly adopted as an alternative approach in engineering, environmental and archeological studies. In the past, several limitation of conventional method in groundwater mapping was always relative to the high cost, time consuming and limited data coverage. Hence, this study adopted an ERT in order to identify the unknown problematic zone due to the excessive groundwater seepage occurrences. During data acquisition, five (five) ERT spread lines was conducted using ABEM SAS4000 equipment set. Then, field raw data was processed using RES2DINV and ROCKWORKS software to generate 2-D and 3- D of the inverse model resistivity section respectively. Engineering properties and information related to the borehole and geochemistry results was also used for interpretation and verification purposes. Geochemistry test was performed to identify groundwater sources using Atomic Absorption Spectrometer (AAS) and Ion Chromatography (IC) in order to determine the elements of cation (sodium, potassium, calcium and magnesium) and anions (chloride, bicarbonate, nitrate and sulfate) respectively. Based on ERT results, it was found that low electrical resistivity value (10 ~ 100 Ωm) which commonly associated to groundwater was detected at ground surface (0 m) until greater depth (> 10 m). Furthermore, it was found that the groundwater was classified as Ca-HCO that indicates the water was originally come from a typical shallow of the fresh groundwater. Finally, this study has successfully demonstrate that the integral application of ERT, geochemistry and borehole data was applicable to produced comprehensive outcome with particular reference to the problematic groundwater seepage assessment

Optimisation of tapioca peel powder as natural coagulant in removing chemical oxygen demand, ammonia nitrogen, turbidity, colour, and suspended solids from leachate sample

Development of natural coagulant is trending these days, especially among the researchers and the practitioners in the water and wastewater treatment industry. In this study, a natural coagulant made from agro-waste of tapioca peel was developed, and its performance had been tested by applying it on the highly polluted wastewater; leachate. The tapioca peel powder (TPP) was extracted from the white flesh of the peel itself. After several processes, the next step was to sundry the solution, and grind the dried tapioca peel until it became a fine powder. A series of jar test was carried out to study the optimisation processes by considering the concentration of the solution, the coagulant dosage, and the pH of the wastewater. Based on the optimisation process, it was determined that TPP worked optimally at 1% concentration, 1,000 mg/L of dosage, and at pH 3 of leachate by removing out 40.3% of chemical oxygen demand (COD), 18.2% of ammonia nitrogen, 85.7% of turbidity, 80.2% of colour, and 85.5% of suspended solids. Hence, it was denoted that TPP could perform satisfactorily at the right conditions with respective optimisation processes