Geotechnical Methods Research Articles

Improving the reliability of calculations of bases and soil massifs based on geotechnical control methods

The article is devoted to the study of geotechnical monitoring during the construction and reconstruction of buildings and structures. The parameters of geotechnical control and the methods necessary for its implementation are considered. Installation of beacons on cracks, periodic measurement of the crack opening width by deformers, microscopes; application of automated systems for measuring crack opening in hard-to-reach places. Geotechnical monitoring is carried out in accordance with the program, which should determine the composition, scope of work, frequency, timing and methods of work that are assigned in relation to the construction or reconstruction object under consideration.

Reliability of CPT measurements in sand – influence of spacing

Geotechnical methods, such as cone penetration tests (CPTs), standard penetration tests (SPTs) and seismic cone penetration tests (sCPTs), are widely used to characterise the in situ properties of soil. In studies where more than one in situ method in close spacing is used, it is important for geotechnical engineers to balance between soil heterogeneity and the artefacts of disturbed testing zones. The same applies if detailed information about the subsoil is required and one in situ method is used in close spacing. There is no consensus on how to define the minimum spacing between testing zones and no study on the effect of disturbance caused by in situ tests. In this study, 33 CPTs were performed in natural sediments in northern Germany and a spacing threshold was defined at which cone resistance is affected by soil disturbance from previously performed CPTs. The CPTs were performed sequentially by successively refining the grid spacing, starting with a spacing of 119 cone diameters between CPTs, to a fine grid spacing of seven cone diameters. The cone resistance is affected by previous CPT measurements below a spacing threshold of 24 cone diameters in medium-dense sands. Silt and clay layers showed no reduction in the cone resistance for the minimum grid spacing of seven cone diameters.

RELATIONSHIP BETWEEN SOIL ENGINEERING PROPERTIES AND CORROSION RATE IN ANDESITIC VOLCANIC SOILS, WEST LAMPUNG, SUMATRA, INDONESIA

Soil is the most diverse environment that can cause metal corrosion. Many researchers claim that soil is a corrosive environment that has complexity compared to other environments. With a background knowledge of soil engineering properties in a specific area and their effects on the metal corrosion process then corrosion problems can be prevented. This paper presents the relationship between andesitic volcanic soil engineering properties with an average corrosion rate based on geotechnical and statistical methods. In this paper, we propose a new average corrosion rate per year on that soil. The study area took place on the Sekincau-Way Tenong Transect Road, West Lampung, Sumatra, Indonesia. This area was composed of silty clay to clayey silt soils which weathering products from andesitic-basaltic volcanic breccia. This soil can store water that is moderate to high and has high plastic properties. Based on the statistical approach, it can be concluded that the corrosion rate in andesitic volcanic soils is 1.132 mm/yr. Soil engineering properties (water content, index plasticity, and clay content) simultaneously affect the average corrosion rate. The effective contribution of each independent variable (soil engineering properties) to the corrosion rate is a plasticity index of 39.5%, the water content of 24.79%, and clay content of 26.04%. Index plasticity and water content were found to raise the average corrosion rate at the soil samples, while clay content was on the side that lowered the average corrosion rate.

Integrated Study of Geotechnical and Geophysical Methods to Assess the Soil Corrosion Potential for Construction Site

Corrosion of subsurface steel structures is very critical issue especially in moisture subsoil. The use ofphysiochemical properties such as pH, salts concentration, electrical resistivity is very common to quantify corrosivenature of subsoil. However, the laboratory measurements of these parameters are quite difficult due to time and budgetconstraints. In this work soil corrosion potential of a power plant site was evaluated using geophysical and geotechnicalinvestigations. Soil samples were collected from 15 boreholes drilled up-to 50 m depth for laboratory testing whereas 3probes of four electrodes vertical electrical sounding (VES) using Wenner configuration were also performed tomeasure the electrical resistivity of the subsurface soil up to 50 m depth. According to the USCS soil system silty clay(CL-ML) was interpreted as dominant material in all boreholes as shallow depth. Poorly graded sand (SP) including silt(SM) was found of variable depth in almost each borehole. The true resistivity values at the depth of 30 meters liesbetween the 19.9 ohm- meters to 59.8 ohm meters. All observation points of electrical resistivity survey VES-I, VES-IIand VES-III near-surface material show moderate soil corrosion potential which is favorable for design of earthing. Upto depth of 4 m, the values of resistivity 52.6 to 59.8 ohm-meters shows adequate estimation of corrosion. According tothe International standard these curves belong to bell type or K type curve of resistivity model. Their resistivity valueswith respect to depth show low to moderate corrosion potential which is satisfactory for construction at this depth afterapplying the nominal cathodic protections. Thus, electric pipe lines may be installed at this depth.

Development characteristics and formation analysis of the Liangjia Village earth fissure in the Weihe Basin, China

Liangjia Village earth fissure, one of the 79 earth fissures along the Kouzhen-Guanshan fault located in the northern Weihe Basin, causes severe damage to buildings and farmlands. Since the late 1950s, 40 earth fissures have occurred in a similar east-west (EW) direction parallel to the Kouzhen-Guanshan fault, and a further 39 earth fissures have occurred with north-west, east-north, or north-east orientations intersecting the fault. In this study, a case study of Liangjia Village earth fissure was conducted to investigate the mechanisms of fissure generation in detail. Geotechnical and geophysical methods including measurements, trenching, drilling, and seismic exploration were used to reveal the basic characteristics, geological background, and origin model of the Liangjia Village earth fissure. This earth fissure, with a total length of 800 m in 2014, runs EW parallel to the Kouzhen-Guanshan fault, and it has damaged buildings and farmlands by forming sinkholes, gullies, subsidence, and a scarp. The trenching results indicated that this fissure underwent multi-phase activity. Analysis of geological drilling and shallow seismic profiling results showed that the fissure also possessed characteristics of a synsedimentary fault. Regarding its genesis, the fissure was formed through the combined actions of three factors: an earthquake created the fissure, the Kouzhen-Guanshan fault controlled its development, and loess erosion and groundwater runoff subsequently enlarged the fissure. Regional extension first generated many buried faults along the hanging wall of the Kouzhen-Guanshan fault before seismic activity caused the buried faults to propagate to the surface, where loess erosion and ground-water runoff promoted the formation of the current earth fissure.

Modelling and monitoring of security unique underground structures of the sewerage system of major towns in difficult ground conditions

On the basis of many years of experience in the construction, reconstruction and operation of underground engineering infrastructure of the metropolis developed the concept and philosophy of the creation and operation of Geomonitoring security system of the tunnel collector. The philosophy of construction of space-time structure of Geomonitoring is described. The article presents the experience of modeling, monitoring and taking protective measures aimed at ensuring the safety of tunnel reservoirs located in the area exposed to the geotechnical effects of underground and high-rise construction. The analysis of calculation and experimental data and the results of long-term monitoring aimed at ensuring the safety of underground drainage and treatment facilities of megepolis. The special protection against technogenic influence is required for long-operated tunnel sewage collectors. This paper, based on the extensive data of studying the work of the tunnel collectors in conditions of soft soils and intense technogenic influences, describes new methods of diagnosing, the features of defects, and the results of modeling joint interaction of the “tunnel – soil bulk” as well as experimental data on experimental objects. The geotechnical methods for protecting the long-operated tunnel collectors have been developed, and there has been given the unique experience of their application in the objects of St. Petersburg together with their monitoring support.

The Methods Used in Monitoring of Large Dams in Turkey

Turkey is a very rich country in terms of water resources. However, in order to use these resources efficiently, water must be stored safely. In this context, the best form of storage is the construction of dams. In our country, large dams, which are among the world's important dams, are being built. Although there are many advantages of large dams, the loss of life and property will be so great in case of a possible deformation or destruction. The fact that dams are under the influence of various forces, as well as being located in the earthquake zone of our country, necessitates continuous monitoring of our dams. Dams are generally monitored using geodetic methods and geotechnical devices. However, mostly details of these two methods are evaluated separately in dam monitoring. Evaluating the results of both methods together is very important for the comprehensive monitoring of the dam and the correct interpretation of possible deformations. In this study, large dams in our country and monitoring studies carried out by using geodetic and geotechnical methods in these dams are given in detail.

Geoelectrical and geotechnical investigation of foundation failure in and around Oroke high school, Akungba- Akoko, southwestern Nigeria

Engineering structures are designed and constructed with an air of lifelong expectancy. Moreover, building foundation may experience failure due to presence of concealed geologic features such as cavity and shear zones which can lead to subsurface subsidence. Hence, it is imperative, prior to building construction, to investigate the physical properties of foundation soils and determine its suitability for design and construction of building structures. In the light of this, a geoelectric survey, involving three (3) electrical dipole - dipole array and geotechnical analysis methods were carried out around a distressed building at Oroke High School, opposite Adekunle Ajasin University, Akungba Akoko to establish the cause of failure for the structures foundation via delineating the subsurface structural features. The field electrical data were plotted on log –log graph sheets and the resulting curves were interpreted qualitatively by visual inspection, and quantitatively via partial curve matching and computer iteration techniques. For the geotechnical analysis, a total of twelve (12) soil samples were taken from different locations of about 30 meters intervals, at the depth of 1.5 meters. The pseudo – section and electrical sections indicate that the subsurface is heterogeneous in geological composition. The 2D dipole- dipole resistivity and pseudo – section delineated zones having resistivity values ranging from 200 to 700ohm meter, and those approaching infinity all within a depth of 0-5 m, the resistivity values of 27 to 139ohm meter suggest the presence of clay. The geoelectric section identified three subsurface geologic layers comprising clay /sandy, clay top soil / sub grade soil, clay / sandy clay and sand weathered layer and the basement (fresh) beneath the failed segment. Additionally, prominent fractures were discovered within some areas on the pseudo-sections. The results of the laboratory tests also included those of natural moisture content, specific gravity, grain size distribution curves, Atterberg limit, compaction test and California Bearing Ratio (CBR). In conclusion, electrical resistivity method was found to be an effective measure or tool in the site characterization. The soil/rock in these zones may require reinforcement in order to enhance its bearing capacity and increase the life span of the engineering foundation. Â

Study on geotechnical engineering investigation method of strong karst deep backfill area in mountain area

Guizhou Province is characterized as mountainous with few flat lands. It also features undulating terrains; widespread karst strata; large karst troughs; karst depressions and falling water caves; and well-developed underground karst caves, karst pipelines, and underground rivers. In such mountainous areas, large-scale construction of karst sites requires large-scale excavation and backfilling. The study site comprises several backfilled layers of 550 m thickness and features complex components and large thickness variations. The influence of the long-term seepage of surface water and groundwater is also apparent. However, the study site also exhibits an uneven settlement of deep backfilled layers and unstable karst foundation. The conventional survey method cannot identify effectively and comprehensively existing problems in engineering geology and hydrogeology according to the problems found in the investigation of large-scale building areas, municipal roads, urban rail transit, and university campuses. Through the combination of building engineering methods, such as new and old topographic and geomorphologic contrast methods, on-site geological surveys, karst hydrogeological surveys, borehole layout principle, drilling method, effective physical exploration test, field in-situ test, and indoor test, the scale and characteristics of karst development in the study site, changes in backfill thickness and material composition, and physical and mechanical properties of rock and soil mass are determined. The results provide comprehensive geotechnical data for the type selection, arrangement, and foundation scheme selection of structures. Through comprehensive analysis and summary, this work establishes a set of comprehensive geotechnical investigation methods for strong backfilled karst areas in mountainous regions. The results are expected to be applicable to other similar sites.

Geophysical Methods and their Applications in Dam Safety Monitoring

The use of geophysical methods in dam sites investigations and safety monitory has proved their good value and versatility in many earthfill dam sites as early as the 1920s. In the following years great development has occurred in the methods, application procedures and tools used. They may be considered today as good ways for carrying out observation tasks on existing dams in non-intrusive and much faster and cheaper ways than the traditional geotechnical methods. It is possible using them to discover anomalies in the dam body or its foundation at an early stage and allowing quick intervention repair works. These methods seek to register and present variations in the basic geotechnical material properties in dams such as; bulk density, moisture content, elasticity, mechanical properties of rocks, electrical resistivity and mineralogy and magnetic properties and so forth. Such variations can indicate increasing seepage flow, progression in cracks’ sizes, formation of voids, caverns and other instability manifestations. Depending on how any investigation is carried out and the targeted anomaly, there is now selection of these methods such as: Electromagnetic Profiling (EM), Electrical Resistivity Tomography (ERT), SelfPotential (SP), Ground Penetration Radar (GPR), variety of Seismic Methods (SM) which can be applied using such equipment as in Seismic refraction, Seismic Reflection, Multi Analysis of Rayleigh surface waves (MASW) instruments, or using Refraction Micrometer (ReMi), macro-gravity method, and Cross-Hole Seismic Tomography. In addition, Temperature Measurements and other less used methods can be used like Microgravity measurement, Magnetic Profiling and Radio Magnetotelluric methods. An attempt is made here to cover the details of these methods, their advantages and limitations and to prove their usefulness in many dam sites all over the world. One observed issue is their adaptability to embankment dams more than to concrete dams and their popularity for checking seepage related problems and material changes within dam bodies and their foundations such as formation of voids and sinkholes.

Determination of geological structures by geophysical and geotechnical techniques in Kırklartepe Dam Site (Turkey)

In foundation research of engineering structures, application of geophysics methods before drilling work allows not only more economical studies but also a more detailed determination of underground sections. Especially in pre-feasibility studies on long tunnel routes, dam sites and lake areas, it has a vital importance in terms of structural safety to determine possible underground buried fault lines, lithology changes, anticlinal-synclinal structures and underground openings. By considering these effective factors, the alluvium/bedrock border and the positions of potential buried faults in the dam site and lake area in the Kırklartepe area of the province of Bayburt in northeastern Turkey were determined by comparison with geophysical and geotechnical methods. First of all, the resistivity of the dam axis location and the change of the Vp wave velocity by depth were determined by comparing the results between geophysical methods of electrical resistivity tomography (ERT) and seismic refraction tomography (SRT), respectively. Afterwards, from the foundation boreholes opened in the dam axis location, joint frequency and the other parameters determined by observations were obtained. With these parameters, 2-dimensional zoning profiles of the dam axis location were formed, and the alluvium-bedrock border and the locations of the buried faults were determined. Two potential faults in the NW-SE direction relative to the location of the dam axis were clearly revealed in the zoning profiles obtained in the ERT and SRT measurements. Additionally, the presence of these faults was determined as a result of examining the separation and joint frequency parameters from the drilling core samples collected from the BH_3 and BH_5 boreholes opened in the investigated area based on changes in the vertical and horizontal directions. In addition to these, in the ERT study, two potential faults other than the determined two were also detected. It was seen in the zoning profiles that these faults corresponded to right under the BH_2 borehole and 60 m SW of the BH_6 drilling. Consequently, in the zoning studies conducted at the examined site, the change in the lithology at the dam axis by depth (alluvium-bedrock border), lateral correlations of boreholes and potential faults were determined. It was recommended for the selected dam axis location to be constructed at a more suitable place in the NW direction in terms of engineering. Furthermore, with this study, it was revealed once again that it is highly essential to use geophysical and geotechnical together in conceptualizing large engineering structure projects.

Automatic control method of construction quality of geological survey in geotechnical engineering

In view of the low efficiency and low automation of the traditional geotechnical engineering geological survey construction quality control method, this paper puts forward the construction quality automatic control method of geotechnical engineering geological survey. The finite element model of geotechnical engineering geological investigation is established by using CRM geological model transformation method. According to the numerical analysis method, the boundary area is cut, and according to the characteristics of the geological model, the volume mesh model is generated by multi-spatial domain method, and the generated model is imported into the finite element analysis system. The finite element model of automatic control platform of full hydraulic core drilling machine is designed. The drilling pressure control method is used to control the drilling pressure in the process of measurement, and the rammed expanded pile with composite carrier is used for construction. The experimental results show that the method can establish the finite element model with high speed and precision on the basis of realizing the automatic control of the construction quality of geological survey in geotechnical engineering. The utility model has the advantages of high precision, small size, strong anti-interference ability, and low cost.

A Robust and Efficient Method of Designing Piles for Landslide Stabilization

ABSTRACT Stabilizing pile is a widely used method to reduce the development of large-scale landslides. Optimizing the pile geometry is a great challenge in the design of stabilizing piles with the purpose of cost-effectiveness, especially for soil strength parameters with large uncertainty. The objective of this study is to propose a robust and efficient method of designing piles for landslide stabilization with the consideration of the safety of slope, uncertainty of soil parameters, and cost of stabilizing piles. A new response surface, which incorporates soil parameters and stabilizing force into a quadratic polynomial function, is first proposed. Unknown coefficients of the quadratic polynomial function are solved with a numerical method at typical sampling points. Based on the solved quadratic polynomial function, the mean and standard deviation of factor of safety (FOS) of the pile-stabilized slope as well as the signal-to-noise factor are then calculated in order to evaluate the design robustness. A framework based on the concept of robust geotechnical design is presented, and its feasibility is illustrated by two cases of soil slopes. The results indicate that the proposed robust geotechnical design method could be used to optimize the design of landslide-stabilizing piles.

Analysis of parallel spatial partitioning algorithms for GPU based DEM

Abstract The capability of solving a geotechnical discrete element method (DEM) applications is determined by the complexity of the simulation and its computational requirements. Collision detection algorithms are fundamental to resolve the mechanical collisions between millions of particles efficiently. These algorithms are a bottleneck for many DEM applications resulting in excessive memory usage or poor computational performance. In particular, for GPU based DEM, there are many factors for a user to consider when deciding on an algorithm. This study discusses a set of diverse classes of geotechnical problems and the impact of algorithm choice. Four factors were considered: i) the world domain size, number of particles and particle density, ii) polydispersity in size, iii) the time evolution and iv) the particle shape. This study shows that for spherical particles, the choice of broad-phase collision detection algorithm has the most impact on computational performance. The computational cost for convex polyhedral particles is dominated by the selection of the particles’ bounding volumes and their intersection tests over the selection of the broad-phase collision detection algorithm. On average for convex polyhedral particles, the broad-phase occupies at most 1.3% of the total runtime, while the narrow-phase collision detection and collision response require more than 87% of the runtime. A combination of bounding spheres and axis-aligned bounding boxes for use as bounding volumes of particles showed the best performance reducing the computational cost by 20%. This study serves as a guide for further research in the field of GPU based DEM collision detection and the application in geotechnics.

Study of Soil Layer Stratigraphy Based on Georesistivity and Geological Techniques

The purpose of study was to determine the structure of the studied soil layer based on measurement of geo-resistivity with the Wenner configuration and geotechnical drilling method. Geotechnical drilling was one way of soil/rock investigations to determine the parameters soil layers. Based on the objective, field tests and laboratory tests were carried out to support scientific investigations. The results of measurements in the field using geo-resistivity were performed to a depth of 23 meters, resulted in 2 types of soil sediment layers namely clay and sand. At a depth of approx. 8 meters, the groundwater level was found and through laboratory tests, the results of geotechnical drilling gave 2 types of soil classification to a depth of 15 meters, i.e CH and ML. In general, the results of the geo-electrical and drilling tests represented the soil real conditions in developing the stratigraphy of the subsurface layer of the soil. It showed that in the first layer, the sediment layer resulting from the breakdown of the initial rock or sediment layer which had undergone transportation of sedimentary layers in the form of clay, silt or sand and did not experience compaction so that it has a large resistivity value. The next layer associated with regional geological maps are dominated by sand.

The sediment record of the Unicorn Cave, southern Harz Mountains, Germany

We demonstrate the utility of a multi-pronged approach to geomorphological studies. We show how the synthesis of results from 3-D imaging, varied geotechnical methods, and dating, reveals hitherto unknown features of a cave and of its sediment infill, and elucidates its geomorphological history. The Unicorn Cave (Einhornhöhle, southern Harz Mountains, Germany), long famous for its cave bear, lion, and mammoth fossils, is a dry vadose trunk cave high above base level, characterized by large rooms connected by shallow passages, and filled with sediments up to 40 m thick. The sediment is an archive for natural and anthropogenic environmental change: the succession of river gravels, breccia, and silts and sands provides a paleo-geomorphic and climatic archive; while human artefacts from the Paleolithic period provide information about early settlement phases. Here we derive a detailed description of the Unicorn Cave and its sediment infill by utilising several sources: (i) We synthesise data from the literature into a comprehensive picture of the sediment infill; (ii) We present new geophysical measurements of the sediments in the large room Leibnizhalle, and discuss these new measurements in view of our older findings; (iii) We map the larger chambers with the photogrammetric structure-from-motion method to build three-dimensional models; (iv) We present new age estimates from speleothem samples in the cave and discuss them with other, published, age estimates. Finally we use our newly collected evidence to reconstruct the evolution of the entire Unicorn Cave (including the newly-revealed, not-yet-accessible passages and their pristine sediment infill, as yet undisturbed by fossil hunters). The main period of speleogenesis ended with base-level incision in the mid-Pleistocene; the deposition of basal river gravels, probably in the late Cromerian, was followed by a sequence of clays and loams, capped by speleothem at ~MIS 3; the dates suggest at least two bone beds (MIS 3, and MIS 5e), along with bone material older than MIS 7.

Subsurface void mapping using geophysical and geotechnical techniques with uncertainties estimation: case study of Kinta Valley, Perak, Malaysia

In this study, an assessment of the subsurface conditions was carried out using both the geophysical and geotechnical methods for delineating lithology units and mapping cavities in the subsurface. In light of this, geo-electrical vertical electrical soundings (VES) technique and drilling tests from which in situ standard penetration tests (SPT-N) and particle size distribution (PSD) analysis on some selected samples were carried out. Additionally, accuracy assessment of the field measurements was carried out statistically using coverage factor and uncertainty analysis at 95% confidence level in justification of the relationship between the estimated depth of the cavity and the resistivity values. The results of VES and 2D resistivity imaging show that three layers are delineated. The weathered bedrock with resistivity of about 500 Ωm hosts the cavity which is air-filled at shallow depth and saturated with fluid or clay with low resistivity of about 127 Ωm at deeper depth. The SPT N-values obtained ranges between 0–5 and 10–20 corresponding to weak/unconsolidated zone and consolidated sediments, respectively. The SPT N-values from the boreholes drilled agreed with the inferred lithology units from electrical resistivity survey. The results of the PSD suggest that sand/gravel sediments with grain sizes more than 0.075 mm dominated the study area. A combination of both the geophysical and geotechnical data shows good agreement and their relevance in addressing subsurface problems.

Subsoil Characterization for Foundation Stability Using Geophysical and Geotechnical Methods

An Integrated geophysical and geotechnical subsoil characterization of parts of the new stadium complex, Akure, southwestern Nigeria had been carried out with a view to characterize the subsoil materials for stability of proposed engineering foundation. Five (5) magnetic and three (3) dipole-dipole profiling were carried out at station separation of 10 m along the traverses. Twenty one (21) Vertical Electrical Sounding (VES) measurements were made at selected locations along the traverses. A total of five (5) soil samples were collected from a dug pit at a depth of 1.0 m for laboratory analysis. The magnetic profiles delineated characteristic one to two negative peak amplitude anomalies that are typical of thin dipping dyke models (suspected to be fractures, shear zones, faults or geological contacts) along Traverses 1-5. The 2-D geomagnetic section delineated overburden thicknesses ranging from 5 – 15 m along the Traverses. The subsurface geologic units delineated by the geoelectric sections and the 2-D resistivity images consisting of the topsoil, weathered layer, partly weathered/fractured basement and fresh bedrock. Part of the topsoil and the weathered layer are characterized by low resistivity values suggestive of the presence of clay and or weak geomaterials at a depth range of 1 – 4 m within which civil engineering foundation are usually placed. These zones and the fractured/fault zones delineated by the magnetic methods constitute weak geomaterials that are considered to be inimical to civil engineering structures within the study area. Results of geotechnical analysis of soil samples adjudged plasticity indices of samples A, C and D to be of high index and were characterized by high plasticity/compressibility and consequently of low engineering competence. Samples B and E were classified as low-medium plasticity/compressibility, and are rated moderate–high engineering competence. However, it was observed that soil with higher liquid limits or plasticity index have lower electrical resistivity values and hence were adjudged low in engineering foundation competence. Based on the analysis of the results obtained from this study, the engineering foundation suitability of the soil were generally classified as good (B and E), fair (D) and poor (A and C). It can therefore be concluded that the subsoil in the investigated area are generally of low to high civil engineering competence. Keywords: Geophysical; Geotechnical; Subsoil; Competence; Characterization; Foundation, Stability. DOI: 10.7176/JEES/10-6-08 Publication date: June 30 th 2020

PREDICTION OF SOIL LIQUEFACTION PHENOMENON IN BANDA ACEH AND ACEH BESAR, INDONESIA USING ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT)

One of the global geohazard issues discuss among scientists is soil liquefaction phenomenon. The incidents occurred at Palu in September 2018 and Aceh in December 2004, triggered soil liquefaction phenomenon which lead severe damages and lives. The common research on the geohazard issue include geotechnical methods (SPT and CPT) and geophysical methods (MASW and seismic). This study was conducted at Meuraxa district (Banda Aceh) and Baitussalam district (Aceh Besar) to introduce the capability of Electrical Resistivity Tomography (ERT) to predict the soil liquefaction phenomenon. The 2-D resistivity data were process using res2dinv inversion software to produce resistivity inversion models which then correlated with published results. The study identified that the resistivity values of 0.1 – 10 Ωm is a soil saturated zone which affected by seawater intrusion and concludes that the study areas predicted by ERT have a high potential of soil liquefaction phenomenon to be occurred.

In-situ foundation characterization and design in Ese Odo Local Government Area of Ondo State, Southwestern Nigeria

This study aims at assessing and characterizing the subsoil types/profile to determine the engineering characteristics of the underlying soils and provide appropriate foundation design alternatives, in Ese Odo area of Ondo State, Nigeria using geophysical and geotechnical methods. The geophysical method involved six vertical electrical soundings (VES) and complemented by two cone penetrometer tests and eight trial pits/boring where representative soil samples were obtained and analyzed in the laboratory, in accordance with relevant geotechnical engineering standards. The VES shows a predominant HK and KHK curve types which account for 33.3 % each. The upper 5 m is characterized by moderate thickness (3.3 – 9.6 m) which could dissipate the influence of structural load effectively and high resistivity values (380 – 2439 ohm-m) to sustain the structural load. The average bearing capacity of 100 KN/m2 is recommended for design of bases/footings for shallow foundation at a depth not less than 2.8 m in the area with the total settlement less than 50 mm tolerable limit, for foundation width ranging from 0.5 to 3.0 m. The recommended range of allowable bearing capacity for strip foundation is 221 - 459 KN/m2, while square is 352 - 641 KN/m2. For driven pile at 5 m, 10 m, and 15 m, the adopted allowable capacity varies between 66 – 118 KN, 212 – 357 KN, and 440 – 717 KN respectively. The allowable bearing capacity for bored pile ranges from 35 – 71 KN, 88 – 170 KN, and 159 – 297 at depth levels of 5 m, 10 m, and 15 m respectively.