Rosli Saad

Soil resistivity measurements to predict moisture content and density in loose and dense soil

In the past, most of the soil electrical resistivity charts were developed based on stand-alone geomaterial classification with minimal contribution to its relationship to some of geotechnical parameters. Furthermore, the values cited a very wide range of resistivity with sometimes overlapping values and having little significance to specific soil condition. As a result, it created some ambiguities during the interpretation of observations which were traditionally based on qualitative anomaly judgments of experts and experienced people. Hence, this study presents soil resistivity values based on laboratory experiment with a view to predict the soil moisture content and density in loose and dense soils. This study used a soil box and a resistivity meter to test a clayey silt soil, increasing its water usage from 1-3% based on 1500 gram of dry soil. All the moisture contents and density data were observed concurrently with 25 electrical soil resistance observations being made on the soil. All testing and formula used were in accordance with that specified in BS1377 (1990). It was apparent that the soil resistivity value was different under loose (L) and compact (C) condition with moisture content (w) and density (ρbulk) correlations being established as follows; ρbulk(C) = 2.5991ρ-0.037, ρbulk (L) = -0.111 ln (ρ) + 1.7605, w(L) = 109.98ρ-0.268, and w(C) = 121.88ρ-0.363 with determination coefficients, R2 that ranged between 0.69 0.89. This research therefore contributes a means of predicting these geotechnical parameters by related persons such as geophysicist, engineers and geologist who use these resistivity techniques in ground exploration.

Correlation Analysis Between Field Electrical Resistivity Value (ERV) and Basic Geotechnical Properties (BGP)

Past applications of electrical resistivity surveying have particularly focused on areas of subsurface ground investigations to locate boulder, bedrock, water table, etc. Traditionally, electrical resistivity surveys were directed by an expert geophysicist for data acquisition, processing and interpretation. The final outcome from the electrical resistivity technique was an anomaly image that helped describe and demarcate zones of challenging ground conditions. The anomalies highlighted uncertain geotechnical conditions that were often irregular and dependent on individual site condition, yielding a site-dependent electrical resistivity value (ERV) for the ground. This study therefore identifies co-relationships between ERV and some basic geotechnical properties (BGP) such as soil moisture content, grain size of geomaterial, density, porosity, void ratio, and Atterberg limit. Different soil samples were collected and tested under both field and laboratory conditions. Basic geotechnical properties of the samples were obtained immediately after the electrical resistivity measurements were made. It was shown that the electrical resistivity value was greatly influenced by the geotechnical properties, and thus the resistivity surveying technique is applicable to support and enhance the conventional stand-alone anomaly outcome that is traditionally used in ground investigation interpretation.

Soil moisture content and density prediction using laboratory resistivity experiment

Natural soils are an intimate mixture of solid, liquid and gas phases. This study establishes a correlation for moisture content and density of a soil with its electrical resistivity. In the past, most of the conventional geotechnical site investigation required bulky and heavy equipment to determine the geotechnical parameters necessary for design and construction purposes. Consequentially, time and cost of the project is increased especially when dealing with some difficult site such as on mountainous terrain. This study is based on laboratory soil box resistivity meter observations made on soils mixed with additions of consistent increments of 1-5 % of water to 1500 gram of remolded soils in loose condition. At least 24 repetitive resistivity test observations were made and the moisture content and soil density was determined concurrently for each of the tests. The observations showed that the electrical resistivity variation decreased in a curvilinear manner with increasing percentage of moisture content. A regression equation and coefficient of determination, R2 for moisture content against soil electrical resistivity value was established by moisture content, w = 152.87ρ-0.312 (ρ = soil electrical resistivity) and R2 = 0.7718 respectively. While a regression equation and R2 value for bulk density versus soil electrical resistivity value was observed to be ρbulk = -0.107 ln (ρ) + 1.7249 and 0.7016 respectively. Hence, a viable method is demonstrated where the electrical resistivity value was applicable and has a great potential for geotechnical data prediction of parameters such as moisture content and soil density.

The Influence of Basic Physical Properties of Soil on its Electrical Resistivity Value under Loose and Dense Condition

Electrical resistivity technique has become a famous alternative tool in subsurface characterization. In the past, several interpretations of electrical resistivity results were unable to be delivered in a strong justification due to lack of appreciation of soil mechanics. Traditionally, interpreters will come out with different conclusion which commonly from qualitative point of view thus creating some uncertainty regarding the result reliability. Most engineers desire to apply any techniques in their project which are able to provide some clear justification with strong, reliable and meaningful results. In order to reduce the problem, this study presents the influence of basic physical properties of soil due to the electrical resistivity value under loose and dense condition. Two different conditions of soil embankment model were tested under electrical resistivity test and basic geotechnical test. It was found that the electrical resistivity value (ERV, ρ) was highly influenced by the variations of soil basic physical properties (BPP) with particular reference to moisture content (w), densities (ρbulk/dry), void ratio (e), porosity (η) and particle grain fraction (d) of soil. Strong relationship between ERV and BPP can be clearly presents such as ρ ∞ 1/w, ρ ∞ 1/ρbulk/dry, ρ ∞ e and ρ ∞ η. This study therefore contributes a means of ERV data interpretation using BPP in order to reduce ambiguity of ERV result and interpretation discussed among related persons such as geophysicist, engineers and geologist who applied these electrical resistivity techniques in subsurface profile assessment.

The Influence of Electrical Resistivity Array on its Soil Electrical Resistivity Value

Electrical resistivity technique has become a popular alternative tool by the geotechnical engineers in subsurface investigation. This study presents the influence of soil electrical resistivity value (ERV) due to the different types of electrical resistivity array used in practice. The dissimilarity of ERV was become a popular debate by the engineers which posses less fundamental knowledge in this area. In the past, the theory of electrical resistivity technique was less being discovered by the engineer which creates lots of black boxes during the utilization of electrical resistivity method (ERM) in engineering purposes. Hence, the result which produced from the ERM was difficult to deliver in a sound of definitive ways due to lack of knowledge and experienced of most engineers. Hence, this study presents the influence of soil ERV due to the different types of array used with particular reference to as Dipole-dipole and Pole-dipole. A line of electrical resistivity imaging was performed on small embankment of sandy and lateritic soil with different types of array using ABEM SAS (4000) equipment. Three in line of soil samples were tested for moisture content (w) test immediately after the electrical resistivity data acquisition was completely measured. Moreover, particle size distribution test also was performed for all soil samples in order to support the findings. It was found that the ERV was never be the same for each types of array used even on the same particular location of the survey line. However, it was found that there was a consistent relationship between ERV and moisture content for both types of soil tested which can be represent by ERV 1/w. Hence, it was found that ERV produced was relative to the types of array used during the field measurement. Each types of array were applicable to be used in subsurface profiling and its selection was subjected to the target of interest.

Volumetric Assessment of Leachate from Solid Waste Using 2D and 3D Electrical Resistivity Imaging

This paper presents an approach to estimate volume of leachate from municipal solid waste using 2D and 3D electrical resistivity imaging. This process is a deviation from Water Balance Method (WBM) that is commonly used for leachate quantification at landfill sites. While the WBM emphasis is on generating rate, this geophysical approach estimates the in-situ total quantity of leachate. Five 100m profiles were used to generate five 2D inverted pseudo-sections and a 3D inverted section using RES2DINV and RES3DINV programs respectively. The resistivity of inverted pseudo-sections clearly delineated the contaminant leachate plume (ρ < 5 Ωm), which facilitated its volume estimation. The effective porosity values of clay (0.15) and sand/gravel (0.28) deduced from lithology logs were used in calculating the imaged volume of the leachate. To confirm the measured resistivity variation in the saturated subsurface around the dumpsite, in-situ electrical conductivity values of 1782 μS/cm and 4521 μS/cm were determined for uncontaminated and contaminated zones respectively. A total leachate volume of 2.21 x 103 was estimated for the 1600 survey area.

Enhancement in Electrical Resistivity Tomography Resolution for Environmental and Engineering Geophysical Study

The Geophysical surveys, including electrical resistivity tomography, are an ideal for many environmental and engineering geophysical studies about the Earth’s subsurface characterizations. This paper present application of electrical resistivity tomography method in two different sites condition and sites investigation purpose. The first investigation site is located in Penang Island and the second investigation site in Perak, Malaysia. There are two different optimized arrays used in our data acquisition, which are wenner-schlumberger array and pole-dipole array. In this study, we are using single channel for the wenner-schlumberger array and multi-channel system for the pole-dipole array. Interestingly, we have used merge data level technique for these two arrays in order to aim for better improvement in electrical resistivity tomography resolution results known as inverse modeling models. As we are considering electrical resistivity tomography results with the geological reference such as borehole record, it shows that the technique is applicable and has their technical merit. The accuracy and their technical viability can be assured by the electrical resistivity tomography result models and thus it is applicable in environmental and engineering geophysical studies.

Enhanced Horizontal and Vertical Resolution in 4-D Electrical Resistivity Tomography for Environmental Slope Study in Penang Island

This paper presents 4-D high resolution electrical resistivity tomography study for slope monitoring using two optimized (modified) arrays of the Wenner-Schlumberger and Pole-Dipole. These optimized resistivity arrays give a total of 2052 number of datum points from each data acquisition set. These two optimized were used because they have more datum points compared to their original arrays. Perhaps these optimized arrays were able to resolve the subsurface structures from surface areas. Inversion results from the computer (mathematical models) suggested that these optimized arrays were able to give in imaging the Earth’s subsurface structures and characterization at different period of time. Furthermore, in this paper, we are presented merging data levels in order to give high resolution in electrical resistivity tomography. Even though the time taken for data acquisition using this technique is twice, the outcome is compromised and reliable which helpful in the Earth’s subsurface interpretation.

Enhancement in resistivity resolution based on the data sets amalgamation technique at Bukit Bunuh, Perak, Malaysia

In this paper, we have carried out a study with the main objective to enhance the resolution of the electrical resistivity inversion model by introducing the data sets amalgamation technique to be used in the data processing stage. Based on the model resistivity with topography results, the data sets amalgamation technique for pole-dipole and wenner- schlumberger arrays are successful in identifying the boundary or interface of the overburden and weathered granite. Although the electrical resistivity method is well known, the proper selection of an array and appropriate inversion parameters setting such as damping factors are important in order to achieve the study objective and to image the target at the Earths subsurface characterizations.

Excavatability Assessment of Weathered Sedimentary Rock Mass Using Seismic Velocity Method

Seismic refraction method is one of the most popular methods in assessing surface excavation. The main objective of the seismic data acquisition is to delineate the subsurface into velocity profiles as different velocity can be correlated to identify different materials. The physical principal used for the determination of excavatability is that seismic waves travel faster through denser material as compared to less consolidated material. In general, a lower velocity indicates material that is soft and a higher velocity indicates more difficult to be excavated. However, a few researchers have noted that seismic velocity method alone does not correlate well with the excavatability of the material. In this study, a seismic velocity method was used in Nusajaya, Johor to assess the accuracy of this seismic velocity method with excavatability of the weathered sedimentary rock mass. A direct ripping run by monitoring the actual production of ripping has been employed at later stage and compared to the ripper ma...