Performance Testing for Slope Instability due to Suffusion via Site-Specific Response Analysis with Incorporation of Electrical Resistivity Tomography

Azrin, Ahmad (2024) Performance Testing for Slope Instability due to Suffusion via Site-Specific Response Analysis with Incorporation of Electrical Resistivity Tomography. PhD thesis, Faculty of Engineering.

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Abstract

Soil instability had caused concerned in geotechnical engineering due to its consequences of failure and its effects to the structures above or surrounding it. The instability of soil is caused by either water, critical stress condition, or perilous void within the soil properties. The lack of proper consideration of critical void in soil or suffusion phenomenon causes soil defects and failures in cut-slopes that subsequently damaging to the economy and ecology. Many researches correlated internal soil instability with water or hydraulic conductivity. This research aims to investigate on internal soil instability caused by void limit state and migration of fines characterized by vibration specifically seismic soil amplification that resemble failure criterion caused by hydraulic load. Soil amplification obtained from sensible conversion of apparent resistivity (ohm.m) to shear wave velocity (m/s) captured by electrical resistivity tomography (ERT) experimental result at specific sites with cut slopes at Pan Borneo Highway, Sarawak, has been studied. Archie’s law which determines porosity is used in this study, where correlation with experimental results have shown its reliability, proving that volume of void over total volume of soil (VV/VT) from soil phase diagram is attainable with ERT and it is equivalent to liquid limit of soil. Energy based analysis is used to actuate synthetic earthquake from underneath and simulates soil amplification, whether it exceeds design response spectra or within limit. Simplified amplitude limit of failure has been developed to alternate Fourier amplitude to propose ERT data collection and new approach to develop serviceability limit state (SLS) or design response limit. Data acquisition via ERT that sensibly converted to shear wave velocity and soil shear strength has been verified its compliance with the existing guideline for slope design from the public works department of Malaysia. Output of this research improved the reliability of design safety factor for any constructions by integrating advanced technology application. As a result, ERT raw soil properties data that correlated well with soil liquid limit where volume of void over total void (VV/VT) is in equivalent and soil conductivity (σ) over soil resistivity (Ω) is consistent with liquidity index. This research also discovered that electrical conductivity against electrical resistivity, 1/Sigma (Σ-1) ÷ Ohm (Ω) = 1 and is a threshold index of soil instability. It is also discovered that when the soil instability index higher than 1 the site-specific soil is unstable. Further research on the instability index is potential and beneficial to the geotechnical engineering industry for geo-hazard identification. In conclusion, this research is focused to give clear interpretation to ERT result and proved that it is useful for future diagnostic of soil stability and its optimum treatment required for future land use.

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