Andy Anderson Bery

Slope Monitoring Study Using Soil Mechanics Properties and 4-D Electrical Resistivity Tomography Methods

In past applications of electrical resistivity survey, users commonly focussed on the Earths subsurface to locate water table, bedrock, etc. Nowadays, this electrical resistivity method is used by engineers for shallow subsurface investigations. This paper presents the integration of soil mechanics properties with electrical resistivity tomography methods and recommends the proper selection of resistivity array (survey planning) and appropriate inversion constraint parameters (data processing) that are able to deliver optimum resistivity tomography model results. This study identifies the empirical correlations of the soils properties such as shear strength parameters, moisture content, void ratio, porosity, saturation degree, and Atterbergs limits with the electrical resistivity values (resistivity tomography models). A total of 11 undisturbed clayey sand soil samples was collected at different distances, depths, and times and were tested under both infield and laboratory conditions during the slope monitoring period. The soil mechanics properties of the soil samples were obtained right after the electrical resistivity survey was made. It is shown that the electrical resistivity values are greatly influenced by the soil mechanics properties. Thus, the electrical resistivity (4-D) survey using the optimized Wenner-Schlumberger array (high data density) is capable of reliably enhancing the conventional outcome of the Earths subsurface investigation.

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.

Empirical Correlation Between Electrical Resistivity and Engineering Properties of Soils

Soils electrical properties are the parameters of natural and artificially created electrical fields in soil and are influenced by distribution of mobile electrical charges, mostly inorganic ions. We aim to determine practically-applicable relations with which to determine soil moisture content and void ratio based on electrical resistivity measurements taken from two different sites in Penang Island. In this study, analysis was conducted to determine the relationship between soil electrical resistivity, moisture content, and void ratio. Moreover, an initial analysis was conducted to determine the variation between the coefficient of gradation with moisture content and void ratio for all data. The developed empirical correlation found in this study can be used as an initial guideline for the further study of tropical soil.

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.

Merge-Optimization Method of Combined Tomography of Seismic Refraction and Resistivity Data

This paper discussed a novel application called merge-optimization method that combines resistivity and seismic refraction data to provide a detailed knowledge of the studied site. This method is interesting because it is able to show strong accuracy of two geophysical imaging methods based on many of data points collected from the conducted geophysical surveys of disparate data sets based strictly on geophysical models as an aid for model integration for two-dimensional environments. The geophysical methods used are high resolution methods. The resistivity imaging used in this survey is able to resolve the subsurface condition of the studied site with low RMS error (less than 2.0%) and 0.5 metre electrodes interval. For seismic refraction method, high resolution of seismic is used for correlation with resistivity results. Geophones spacing is 1.0 metre and the total number of shot-points is 15, which provides very dense data point. The algorithms of merge-optimization have been applied to two data sets collected at the studied site. The resulting images have been proven to be successful because they satisfy the data and are geometrically similar. The regression coefficient found for conductivity-resistivity correlation is 95.2%.

2-D Electrical Resistivity Tomography (ERT) Assessment of Ground Failure in Urban Area

This study was carried out to assess the foundation defects around an urban area in Selangor, Malaysia using 2-D electrical resistivity tomography (ERT). The affected structure is a three storey houses and having severe foundation-based cracks. Six 2-D ERT survey lines with 5 m minimum electrode spacing using Pole-dipole array were executed parallel to buildings wall. Four boreholes were conducted to identify the depth to competent layer to verify the 2-D ERT results. Inversion model of 2-D resistivity show that the study area consists of two main zones. The first zone is a low resistivity value (<100 Ωm), which appears to be a zone that is fully saturated with sandy silt and this could be an influence factor the increasing water level because sandy silt is highly permeable in nature and alluvium (silt, sand and clay), boulder (1200-3500 Ωm) or highly weathered with the resistivity values of 100-1000 Ωm at 20-70 m depth. The second zone is the granite bedrock of more than 3500 Ωm with depth greater than 70 m. These results were complimented and confirmed by borehole records. The ERT and borehole record suggest that the clay, sand, saturated zone, highly weathered zone and boulders at foundation depths may lead to ground movements which affected the stability of the building.

Buried Man-made Structure Imaging using 2-D Resistivity Inversion

This study is carried out with the objective to determine the suitable resistivity inversion method for buried man-made structure (bunker). This study was carried out with two stages. The first stage is suitable array determination using 2-D computerized modeling method. One suitable array is used for the infield resistivity survey to determine the dimension and location of the target. The 2-D resistivity inversion results showed that robust inversion method is suitable to resolve the top and bottom part of the buried bunker as target. In addition, the dimension of the buried bunker is successfully determined with height of 7 m and length of 20 m. The location of this target is located at -10 m until 10 m of the infield resistivity survey line. The 2-D resistivity inversion results obtained in this study showed that the parameters selection is important in order to give the optimum results. These parameters are array type, survey geometry and inversion method used in data processing.

Application of 2-D Resistivity Imaging and Seismic Refraction Method in Identifying the Structural Geological Contact of Sedimentary Lithologies

The interest of this study was to prove the existence of geological contact to field models with presences of outcrops as references. The physical relief of the outcrops can be determined by geological events of faulting, fracture, and folding. Geological contact plays important roles in environmental studies. 2-D resistivity imaging is the best method used for identifying the geological structures of study area located in Guar Jentik, Perlis and Bukit Kukus, Kedah. Besides that, seismic refraction method also applied at the study area. Results from both methods were integrated to get data correlation. There is good correlation produced which have successfully proved the existence of the faults and contact zones in study areas. Resistivity result shows that first study area has two main zones, red mudstone with resistivity value of 1 Ωm – 100 Ωm, sandstone with resistivity value of 2000 Ωm – 9000 Ωm, and Seismic refraction has provided the result on velocity of each zone, mudstone zone is 200 m/s -1800 m/s and sandstone zone is >2000 m/s. The geological contact of fault is determined between the red mudstone zone and sandstone zone. In the second study area, the fracture was found within chert zone and contact zone is located between the chert zone and mudstone zone. In addition, the fold is found to form in the chert zone. Mudstone zone has resistivity value of 1 Ωm – 1500 m/s and chert zone has resistivity value of 2600 Ωm – 35000 Ωm. The first layer of the seismic section is consisting of mudstone with a velocity of 1200 m/s is interpreted as chert zones.

Joint-interpretation of 2-D electrical resistivity method and borehole data for subsurface lithology identification

There have been improvement in the subsurface investigation using non-destructive geophysical method. These were supported by improvement in data inversion method for 2-D resistivity imaging method. This geophysical method have been used for many environmental and engineering studies, such as slope monitoring, cavities detection, buried man-made structures and so on. This paper present the 2-D data inversion in electrical resistivity method which was carried out in Penang, Malaysia. This non-destructive method is used to image the subsurface for soil’s lithology purpose. In addition, two inline boreholes were used to validate and verify the obtained results of electrical resistivity imaging. Based on the electrical resistivity imaging, the subsurface is made up of four type of materials. They are sandy silt, silty sand, sand and lastly weathered granite. Sandy silt and silty sand soils give resistivity values of 65-220 Ωm and 120-770 Ωm. Meanwhile for sand and weathered granite materials, their resistivity values are 220-1400 Ωm and 410-2600 Ω.m respectively. Beside than electrical resistivity imaging, this work also present the distribution of conductivity for the investigated subsurface via the 2-D conductivity model. In conclusion, the used of the non-destructive geophysical method in this study is successful in image the investigated subsurface lithology and the investigation coverage area is enhanced instead of information from two discrete points of the geotechnical boreh oles. Therefore, the joint-interpretation of these two technical methods is capable and reliable to give information about the Earth’s subsurface lithology.There have been improvement in the subsurface investigation using non-destructive geophysical method. These were supported by improvement in data inversion method for 2-D resistivity imaging method. This geophysical method have been used for many environmental and engineering studies, such as slope monitoring, cavities detection, buried man-made structures and so on. This paper present the 2-D data inversion in electrical resistivity method which was carried out in Penang, Malaysia. This non-destructive method is used to image the subsurface for soil’s lithology purpose. In addition, two inline boreholes were used to validate and verify the obtained results of electrical resistivity imaging. Based on the electrical resistivity imaging, the subsurface is made up of four type of materials. They are sandy silt, silty sand, sand and lastly weathered granite. Sandy silt and silty sand soils give resistivity values of 65-220 Ωm and 120-770 Ωm. Meanwhile for sand and weathered granite materials, their resistivit...