Geotechnical Reports Research Articles

DEVELOPMENT OF PEAK GROUND ACCELERATION USING A NON-LINEAR APPROACH TO EVALUATE LIQUEFACTION POTENTIAL IN SEI WAMPU BRIDGE, LANGKAT, NORTH SUMATRA, INDONESIA

The design of building structures requires compliance with seismic codes and all their consequences. Based on geotechnical investigation reports, the construction of Sei Wampu Bridge in Langkat, North Sumatra, Indonesia, is located in an area where the soil layers are predominantly sand with shallow water levels because of its proximity to a river and is a high earthquake zone due to the Semangko fault. That condition will affect the potential of liquefaction occurring. This study aims to identify the liquefaction potential in the Sei Wampu Bridge. Based on Indonesian National Standard (SNI) 1726-2019, sites prone to liquefaction are categorized as site class-specific soil (F) and requires site-specific response analysis (SSRA) methods. Non-linear analysis 1-D is chosen to propagate earthquake waves with the software DEEPSOIL V7. The input parameter for soil movement utilizes an average spectral matching method with a minimum of 7 pairs of soil movement selected from the earthquake recording website, PEER Ground Motion Database. The selection of earthquake considers a 1000-year earthquake load return period, or a 7% probability exceeded within 75 years. Site-specific response analysis (SSRA) resulted in a peak ground acceleration (PGA) value for each borehole depth used in liquefaction potential analysis. Using a historical earthquake scenario with a 6.3 Mw shows that the research location has liquefaction potential at 0 m-15 m deep with high vulnerability levels, where the LPI value reaches 36.21.

Index swelling prediction of clayey soils

In civil engineering, statistical studies are widely used in risk studies of landslides, seismic, swelling-shrinking and other hazard studies. This study deals with a volumetric deformation of the clayey soil by water absorption, which is the phenomenon of swelling. It is a serious problem for lightweight structures such as highways. This phenomenon is characterized by two mechanical parameters measured by an oedometric test carried out in the laboratory, which takes a long time and is expensive, why scientists have always looked for other quick and less expensive alternatives to estimate these parameters. They developed models between classical parameters, easily determined in the laboratory, such as water content, dry density, percent of clay particles, plasticity index and mechanical properties of clay soils. The developed models are based on descriptive statistics, a neural network, or multiple regressions. To estimate the risk of swelling and to verify the applicability of the models of the literature on the Algerian soils, a database was collected from the geotechnical reports carried out on the sites of certain projects in Algeria. The objective of the present study consists of estimating the mechanical parameter of swelling, which is the swelling index from a set of physical tests carried out in the laboratory.

Research on Shear Strength Parameters of the Silty Fine Sand and the Rounded Gravel Layers in Nanning City

The silty fine sand and rounded gravel layers are widely distributed in Nanning City, China. Due to the low clay content, the silty fine sand and rounded gravel layers are prone to disturbance during sampling and transportation, which affects the shear strength test results. The reasonable determination of their shear strength is significant and imperative to the project. The rail transit project in Nanning is under large-scale construction. This work obtained the shear strength of the silty fine sand and the rounded gravel layers by conducting laboratory tests on undisturbed samples from deep foundation pits, combined with large-scale direct shear in situ tests. In addition, geotechnical investigation reports for typical projects in Nanning City were compiled, and the test data for the silty fine sand and the rounded gravel layers were comparatively analyzed using the empirical value. The results show that the shear strength test values of the fine sand layer are consistent with the current standard empirical values, and empirical values can be used for reference. The shear strength test value of the rounded gravel layer has significantly improved compared to the current standard empirical value, with a cohesion (c) value of 0–6.8 kPa and an increase in internal friction angle (φ) of 0%–12.5%. It is recommended to determine the shear strength of the rounded gravel layer based on the actual situation.

Multivariate probability distributions for index and mechanical clay parameters in Shenzhen

Probabilistic site characterization is the cornerstone of data-centric geotechnics, which underpins the digitalization in geotechnical engineering. The essential aspect of probabilistic site characterization is to reasonably infer the probability density distributions of geotechnical parameters, based on field and laboratory data. In this paper, a clay property database, SZ-CLAY/11/5130, was established by collecting geotechnical investigation reports from 52 engineering projects in Shenzhen city. This SZ-CLAY/11/5130 database was first compared with the global clay database CLAY/10/7490 and the Shanghai clay database SH-CLAY/11/4051, in terms of their sample ranges, correlations, and scatter plots. Then, the multivariate probability distribution of eight clay parameters was established using the training records selected from SZ-CLAY/11/5130, to characterize the generic correlations between multiple clay parameters. Based on Bayesian theory, the posterior distributions of clay mechanical parameters from a construction site in Shenzhen city were updated using both the site-specific correlations and the generic correlations given by SZ-CLAY/11/5130. The constructed multivariate probability density distribution is necessary for this updating step.

Estimating Liquefaction Susceptibility Using Machine Learning Algorithms with a Case of Metro Manila, Philippines

Soil liquefaction is a phenomenon that can occur when soil loses strength and behaves like a liquid during an earthquake. A site investigation is essential for determining a site’s susceptibility to liquefaction, and these investigations frequently generate project-specific geotechnical reports. However, many of these reports are frequently stored unused after construction projects are completed. This study suggests that when these unused reports are consolidated and integrated, they can provide valuable information for identifying potential challenges, such as liquefaction. The study evaluates the susceptibility of liquefaction by considering several geotechnical factors modeled by machine learning algorithms. The study estimated site-specific characteristics, such as ground elevation, groundwater table elevation, SPT N-value, soil type, and fines content. Using a calibrated model represented by an equation, the investigation determined several soil properties, including the unit weight and peak ground acceleration (PGA). The study estimated PGA using a linear model, which revealed a significant positive correlation (R2 = 0.89) between PGA, earthquake magnitude, and distance from the seismic source. On the Marikina West Valley Fault, the study also assessed the liquefaction hazard for an anticipated 7.5 M and delineated a map that was validated by prior studies.

Investigation of parameters affecting vibration patterns generated during excavation by EPB TBMs

Tunnel Boring Machines (TBMs) are widely utilized for infrastructure projects and they should be operated in accordance with the geological conditions for reaching favorable excavation rates. Therefore, recognizing any type of variance in the excavation conditions and responding properly and quickly have great importance. In that aspect, vibrations generated during mechanized excavation by Earth Pressure Balance (EPB) TBMs are analyzed and correlated with some parameters along the alignment in the present study. A special vibration data recording system is developed and installed onto four EPB TBMs, excavating in three different project sites. Vibration data on a total of 6 km tunnel excavation is recorded in three orthogonal directions and the effects of geological conditions including soils and hard rocks, EPB TBM operating parameters (thrust, torque, face pressure, cutterhead rotational speed, penetration rate), cutter damages/breakages, positions and types of accelerometers, and TBM diameters on vibration are investigated. Geotechnical characteristics of the investigated alignment are obtained from the geotechnical reports of the related sites. Following the detailed analysis of vibration characteristics (time domain parameters) and geotechnical data, it is seen that the vibration patterns generated during the excavation are greatly influenced by geological and lithological changes. The vibrations are also influenced by the TBM operational parameters and cutter conditions. It is realized that the broken disc cutters create specific high-amplitude signals. Generally, as the rock strength increases, TBM vibrations increase and the vibrations reduce greatly in weathered rocks and soils. These results indicate that TBM vibrations may be used for the identification of geological conditions and worn / broken cutters. The study can be further improved with additional data.

A Case Study of Thin Concrete Wall Elements Subjected to Ground Loads

Smuggling and warfare tunnels are unique structures that have rarely been studied from an engineering perspective. A notable example is the vast networks of tunnels that were secretly constructed underneath the Gaza Strip. Particularly because these tunnels were not designed and constructed via traditional engineering practice, they constitute an interesting case study. The tunnels are supported by thin precast concrete elements, with the wall elements being the critical structural element. While some instances of structural failure and collapse have been reported in the media, a great number of the tunnels have remained stable. In this paper, we attempt to conduct a forward analysis to estimate the load and response of the wall elements. We estimate the range of problem input parameters based on multiple sources, including media accounts, geological research papers, and geotechnical reports obtained from the vicinity of the Gaza tunnels. The problem is then analyzed using two approaches: (1) a simplified structural analysis based on lateral earth-pressure theory and (2) numerical modeling. Both analysis methods show that the wall elements should fail due to compression even under the most favorable estimates of input parameters, in contrast to actual reality. We discuss possible explanations for this disparity. While it is not possible to pinpoint the exact explanation, we argue that current geotechnical practice is generally biased toward conservatism, even prior to the application of safety factors.

Uncertainty Characterization for Soil Cohesion in a Project Site in Nasiriyah Using Bayesian Methods

High uncertainties arias through the characterization of soil parameters because of the lack of data obtained from geotechnical reports. Reducing these uncertainties may improve the characteristic values of soil parameters. This research aims to probabilistically characterize a soil's cohesion parameter in Nasiriyah. The Bayesian approach has been applied to soil data obtained through a project in Nasiriyah. The soil at the site is classified as lean clay, and the soil cohesion has been evaluated using two Bayesian methods: the ordinary, normal distribution method (OND) and the Marcove Chain Monte Carlo-based Bayesian approach (MCMC) method. The previous knowledge utilized in the Bayesian approach was based on 20 boreholes, and the subjective probability approach has functioned in the prior probability distribution. The OND method deduced a mean value of cohesion of (195.9 kPa) and a standard deviation of (14.68 kPa), (COV) 7.49%. It was noted that the probability distribution has a more significant effect than the previous distribution on the posterior distribution. The MCMC method summarized the probabilistic description of the soil characteristic, through which it reached the mean and the subsequent standard deviation (167.49) kPa (109.8) kPa, respectively, and the coefficient of Variation (COV) was 65.6%. It is considered the most appropriate and common method, especially in high-dimensional data when the results are not well known because it can provide a probabilistic value for the not well-known data.

Geotechnical correlations of soil properties in Hilla City – Iraq

AbstractIn this research, the geotechnical properties of the soil profile in Hilla city within Babylon Governorate in the middle parts of Iraq are described. The geotechnical data at the specific sites were collected from some geotechnical investigation reports performed at some selected locations. This article is devoted to studying the distribution of soil properties (the physical and mechanical) in the horizontal and vertical directions. Moreover, a correlation between different physical and mechanical properties is performed. The correlation is executed using statistical analysis by Microsoft Excel Software (2016). From the regression results, it was found that the nature of the soil is cohesive up to 15 m under the natural ground level, and the soil will change to noncohesive. The new line in the plasticity chart has been drawn parallel to A-line especially for the investigated region, the shear strength parameters depend on the consistency of the soil and the depth, and finally, there is a direct correlation between mechanical and physical parameters. Using these correlations with some available information help to predict the value of shear strength and consolidation parameters.

Empirical Correlation between Standard Penetration Resistance (SPT-N) and Shear Wave Velocity (Vs) for Soils in Metro Manila, Philippines

The measurement of the shear wave velocities (Vs) of soils is an important aspect of geotechnical and earthquake engineering, due to its direct relation to the shear modulus (G), which in turn influences the stress–strain behavior of geomaterials. Vs can be directly measured or estimated using a variety of onsite tests or in a laboratory. Methods such as downhole PS logging require boreholes and may not be logistically and economically feasible in all situations. Many researchers have estimated Vs from other geotechnical parameters, such as standard penetration test resistance (SPT-N), by means of empirical correlations. This paper aimed to contribute to this subject by developing an empirical relationship between Vs and SPT-N. Data from twenty sites in Metro Manila were obtained from geotechnical investigation reports. Vs profiles of the same sites were also acquired using the refraction microtremor method. New empirical relationships were developed for all, sandy, and clayey soil types, using a non-linear regression method that is applicable for Metro Manila soils. Statistical evaluation and comparison of the proposed correlations with other previous works suggested the viability of the empirical model.

Introducing Tree-Based-Regression Models for Prediction of Hard Rock TBM Performance with Consideration of Rock Type

Prediction of machine performance is a fundamental step for planning, cost estimation/control and selection of the machine type when using a tunnel boring machine (TBM). Penetration rate (PR) and machine utilization (U) are the two principal measures of TBM performance for evaluating the feasibility of using a machine in a given ground condition. However, despite the widespread use of TBMs and established track records, accurate estimation of machine performance could still be a challenge, particularly in complex geological conditions. Since different types of rocks have varied texture (cementation and grain size), and respond differently to cutting forces in the TBM tunnelling, incorporating the effects of rock type in performance prediction models can improve the accuracy of the estimates. The aim of this study was to develop models for predicting penetration rate of hard rock TBMs in different types of rock based on field penetration index (FPI), using multivariable regression analysis and machine learning algorithm, including classification and regression tree (CART). The proposed models offer estimated FPIs in different rock types, rock strength, and rock mass properties in the form of graphs (diagrams), which can be used to estimate TBM penetration rate. The proposed models have been developed based on the analysis of a comprehensive database of TBM performance in various rock types and offers more accurate estimates of machine performance by incorporating many of the key parameters available in typical geotechnical reports and contract documents. The models also exhibit sensitivity to rock mass parameters for predicting the penetration rate.

Landslide Susceptibility Assessment of Heraklion Prefecture in Crete, Greece

The purpose of this particular study is the assessment of landslide susceptibility of Heraklion prefecture area of Crete Island through geospatial analysis in order to present the general susceptibility zonation, so that it may be used as a basis in future extensive and detailed landslide susceptibility research, which will lead to the prevention of possible future landslides. In order to accomplish this task, it is essential to study the geological, geomorphological, geotectonic, hydrological and hydrogeological characteristics of the area, as well as the land use and compare this information with real landslide occurrence data from the study area. Based on this study it became clear that the area is defined by medium to very steep slopes and a geotechnical and geological setting that are extremely favorable for landslides. These reasons, as well as the fact that this prefecture is known to be the most densely populated prefecture of Crete Island created great interest in this area for research of this kind to prevent the loss of human life and the structural damage of properties. In order to study the landslide susceptibility of Heraklion prefecture, firstly, a geodatabase, which includes the landslide inventory, was created. The landslide inventory is consisted of previous landslides, which were collected from related geotechnical reports with all the essential spatial and descriptive information (such as locations and causes of the landslides). Furthermore, the necessary raster and vector data for the geospatial analysis of the area were obtained. Because the landslide susceptibility is a multifactorial problem it was decided to use a relating method to the problem’s nature, which was the methodology of the Analytical Hierarchy Process (AHP), as it is a simple and widely used method for similar studies, which makes it a great tool for this introductory study. In addition, this method was implemented in a GIS environment. For the purpose of the study, ten (10) triggering factors that cause landslides were defined, followed by the creation of a landslide susceptibility assessment map of the study area, depending on the influence of each factor. In accordance with this map, the highest susceptibility mostly corresponds to the mountainous regions of the prefecture. Finally, the success evaluation of the landslide susceptibility model was determined based on the frequency of landslide occurrences of the medium, high, and very high susceptibility zones. Consequently, the model was characterized as 90.48% successful, according to bibliography and the landslide inventory.

Urban geology from a GIS-based geotechnical system: a case study in a medium-sized city (Oviedo, NW Spain)

This paper describes the development of a GIS-based geotechnical system designed to face challenges on urban geology in a Spanish mid-sized city. Its multipurpose nature is based on a relational database that holds a wide variety of georeferenced ground data, mostly extracted from geotechnical reports or acquired during fieldwork. At present it includes, among other unpublished information, more than 2000 site investigations and the results from 5000 tests carried out on rock, soil and groundwater samples. This desk tool provides a better understanding of the bedrock and superficial geology through the spatial analysis of the collected subsurface data. The main achievements include the classification and mapping of man-made grounds, fluvial sediments and residual soils; the identification of unreported faults; the review and detailed study of geotechnical parameters and properties of the rocks and soils; and the hydrogeological characterization of the permeable units. It also provided the surface geological mapping of the urban area; the development of a geo-engineering map based on lithological, geotechnical and construction criteria; and the creation of a preliminary 3D layer-based ground model of the city centre, where the subsurface contains stone used for heritage buildings listed by UNESCO.

Usefulness of Compiled Geophysical Prospecting Surveys in Groundwater Research in the Metropolitan District of Quito in Northern Ecuador

As in other large Andean cities, the population in the Metropolitan District of Quito (MDQ) in northern Ecuador is growing, and groundwater is becoming essential to meet the increasing urban water demand. Quito’s Public Water Supply Company (EPMAPS) is promoting groundwater research for sustainable water supply, and geophysical prospecting surveys are used to define aquifer geometry and certain transient groundwater features. This paper examines the usefulness of existing geophysical prospecting surveys in groundwater research in the MDQ. A database was built using 23 representative geophysical prospecting surveys compiled from EPMAPS’ public repository, official geotechnical research reports, and the scientific literature. Fifteen EPMAPS-promoted surveys used near-surface electrical techniques (seven used electrical resistivity tomography and eight used vertical electrical sounding) to explore Holocene and Pleistocene sedimentary and volcano-sedimentary formations in the 25–500-m prospecting depth range, some of which form shallow aquifers used for water supply. Four other surveys used near-surface seismic techniques (refraction microtremor) for geotechnical research in civil works. These surveys have been reinterpreted to define shallow aquifer geometry. Finally, four surveys compiled from the scientific literature used electromagnetic techniques (magnetotelluric sounding and other very low-frequency methods) to explore Holocene to late Pliocene formations, some of which form thick regional aquifers catalogued as the larger freshwater reservoirs in the MDQ. However, no geophysical prospecting surveys exploring the complete saturated thickness of the Pliocene aquifers could be compiled. Geophysical prospecting surveys with greater penetration depth are proposed to bridge this research gap, which prevents the accurate assessment of the renewable groundwater fraction of the regional aquifers in the MDQ that can be exploited sustainably.

A geotechnical stratigraphy for the shallow subsurface in the Southern Central Graben, North Sea

The Integration of conventional 3D seismic data with high-resolution 2D seismic data and cone penetration test (CPT) data from geotechnical jack-up foundation reports has enabled a new late Quaternary geotechnical stratigraphy for the Southern Danish Central Graben area in the North Sea. The shallow subsurface has been subdivided into geotechnical units based on seismic appearance and soil behaviour type. The lateral thickness and geotechnical property variations have been mapped and associated with the existing stratigraphies from adjacent areas in the German and British sectors. The geotechnical variations have also been related to geomorphological features in the subsurface that are a result of the changing glacial conditions over the last 120.000 years. Particularly, buried valleys produce unpredictable geotechnical conditions that require additional evaluation and possibly borehole investigations as well as CPTs. The study synthesizes data from multiple geotechnical surveys and extrapolates the local knowledge from the different sites, providing a better regional understanding of the geology and the geotechnical behaviour of the shallow subsurface. • A geotechnical stratigraphy based on seismics and CPT data. • Correlation of seismic facies and geotechnical property distributions. • Regional stratigraphic input to improve risk assessment in offshore construction. • Geotechnical data improves geological evolution models.

Investigation of the factors affecting the ultimate bearing capacity of bridge piles in limestone with a calibrated 3D FEM

In this study, we investigated the behavior of a pile constructed on limestone rock under axial loading using a numerical approach. A parametric study was performed based on the full-scale pile load test results and the geotechnical reports on the site. Different values of unconfined compressive strength were implemented to investigate the pile’s behavior in relation to skin friction resistance only and the combination of end bearing and skin friction resistance. Additionally, we studied the effects of the length/diameter ratio on the pile’s capacity using nine pile load models. Numerical analysis showed that, in the initial loading stage, the applied load was transferred by skin friction only, until a certain displacement value, after which end bearing resistance shared the transferred load with skin friction resistance. Furthermore, there was a strong correlation between the load values measured using the finite element method and the values predicted from other methods used in the literature.

Seismic risk and loss estimation for the building stock in Isfahan: part II—hazard analysis and risk assessment

The second part of a seismic risk assessment study for the Iranian city of Isfahan is presented, focusing on the description of the hazard, the risk analysis, and the discussion of the results. This study utilizes the building exposure model, the fragility and the vulnerability curves illustrated in the companion paper. The earthquake occurrence source model adopted is based on the EMME14 hazard study. The site effects accounting for the soil nonlinear behavior are modeled by means of a Vs30 map derived from the topographical slope. The validity of this map is tested based on the local surface geology and geotechnical reports. The probabilistic seismic hazard maps for different return periods that account for site effects are generated and compared with the design spectra mandated by the Iranian national seismic design code. In addition, direct seismic monetary and human losses are estimated for two earthquake scenarios and also for 100- and 475-year return periods. We show loss maps and loss curves, offering insights on the most vulnerable building classes and the spatial distribution of the estimated losses. The results provide a basis for pre- and post-disaster emergency planning, for global and local urban planning, as well as for conceiving adequate risk mitigation strategies including devising fair earthquake insurance policies. This study may also serve as a blueprint for carrying out similar work in other urban areas of the Middle East.

Geotechnical Baseline Reports – ground models you can just make up?

Geotechnical Baseline Reports (GBRs) are a purely commercial form of ground model, used to allocate ownership of unforeseen ground risk in a construction contract. They are used at tender to provide a common basis for pricing risk and they are used during construction to provide an efficient means of managing claims involving potentially unforeseen ground conditions. One of the ways in which GBRs are different from conventional ground models is that they do not necessarily have to present objective data-based truths about the ground. This possibility arises because clients have varying appetites and abilities to take on construction risk. GBRs can be difficult to write because they are focused on encounters with the ground during construction and these experiences are often indirect and significantly different to encounters in ground investigations. This construction knowledge and the commercial nature of GBRs mean a multi-disciplinary approach to writing GBRs is preferred. The profession best able to characterize the risk inherent in the ground is the engineering geologist through knowledge of ground models. GBR ground models can be considered to be a distinct commercial variant and development of the engineering ground models described in the IAEG's CS25 report on the subject. Thematic collection: This article is part of the Ground models in engineering geology and hydrogeology collection available at: https://www.lyellcollection.org/cc/Ground-models-in-engineering-geology-and-hydrogeology

Digitalization of mechanical and physical properties of Singapore Bukit Timah granite rocks based on borehole data from four sites

The Bukit Timah Granite (BTG) formation is widely distributed in the central and northern parts of Singapore Island. The BTG rocks in the formation vary from granite to granodiorite. Several hybrid rocks and dykes are also present in the BTG. The granite is in various states of fracturing and weathering, ranging from residual soils to intact, unweathered fresh rock. This paper presents some mechanical and physical properties of Singapore BTG rocks, based on data from the Factual Geotechnical Reports of more than 200 boreholes from Downtown Line stage II (DTL2) sites of Cashew, Hillview, Bukit Panjang and Beauty World. The variations of the parameters, including the unconfined compressive strength (UCS), the point-load strength index (Is50), the Cerchar abrasivity index (CAI), and the slake-durability index are derived from laboratory tests on samples from borelogs of different depths. The empirical correlations between the UCS and Is50 and between the CAI and the strength parameters (UCS and Is50) are derived and validated against the commonly adopted equations. Statistical information, including the average values, the standard deviations, and the coefficients of variation, are provided for these parameters. These statistics provide a useful reference for numerical simulations and future projects involving BTG rocks.

British military geology breaks new ground: geologists and geology-related maps used by the Allies in the Italian Campaign of 1943-1945

British armed forces made professional use of only two military geologists as staff officers in World War I, and only two in World War II until June 1943, when appointment of Captain (later Major) J.V. Stephens broke new ground. Stephens landed in Sicily on 10 July 1943, D-Day of the Allied invasion. He served successively in Sicily and mainland Italy, as Staff Officer (Geology) at the headquarters of the Allied armies, assisting planning for advances into enemy-occupied terrain (‘operations’) and development of a military infrastructure within regions when held by the Allies (‘works’). Another geologist staff officer, Major W.A. Macfadyen, arrived in Italy in July 1944, with Allied Forces headquarters for the Mediterranean Theatre of Operations. His duties included fieldwork in Lampedusa, Pantelleria, Corsica and Sicily. The Allies used Italian geological maps reprinted by the Geographical Section General Staff of the British Army; geotechnical maps and reports compiled in England by the Inter- Service Topographical Department; and maps/reports generated in the USA by the Military Geology Unit of the US Geological Survey.