Geotechnical Investigations Research Articles

Seismic characterisation of the subsoil under a historic building: Cathedral Church of Saint Mary in Murcia case study

This research focuses on the Cathedral Church of Saint Mary in Murcia, Spain, which is located in a moderate-to-high seismic risk zone in the Spanish context. The study uses geophysical techniques and geotechnical investigation to characterise seismic ground models at the building's scale, aiming to understand the real amplification of the ground under seismic effect in historic buildings. Three soil layers (silt, sand with gravel, and gravel) were identified through core borings. Multichannel Analysis of Surface Waves (MASW) profiles and Mini-array profiles revealed Vs values of 305 ± 32 m/s, 296 ± 62 m/s, and 440 ± 38.5 m/s, respectively, for these materials. Seismic Refraction Tomography (SRT) showed Vp values of 586 ± 73 m/s, 700 m/s, and 1466 ± 489 m/s for the corresponding layers. The horizontal-to-vertical spectral ratio (HVSR) approach identified a ground predominant period ranging from 0.37 to 0.38 s. Another significant peak at 2.3 s is observed, probably associated to the Triassic basement. Three seismic events with magnitudes Mw between 4.9 and 5.1 were used as inputs to determine the amplification factor (AF). The results indicate a PGA amplification factor between 1.7 and 2.1. These results contribute to the conservation and mitigation of seismic risk of this cultural heritage generating input data that enables precise computation of the soil-structure interaction.

Limitations in Tunnel Portal Design: An Evaluation Using Numerical Models and Line Surveys

In this study, engineering geology and geotechnical design studies of a highway tunnel project, located on the route of Zonguldak-Amasra-Kurucasile, was expressed. Owing to the low overburden thickness the subjected slope tunnel, especially the right tube in accordance with the project kilometer incremental direction, will be exposed to asymmetrical load after commence of the excavation. Besides, thicknesses between right tube right wall and the slope face in this section has decreased up to 6 m level. Moreover, as the tunnel is passing under the 1st grade archeological protection area, some of the site investigation studies, such as geotechnical drilling and site laboratory works could not have been performed. Thus, this study is explaining the determination of excavation support system of slope tunnel by using engineering geology studies and numerical models. As the tunnel site is located under the 1st grade archeological protection area, any of the required geotechnical site investigation drilling studies and corresponding site testing was not performed on the tunnel axis. Instead of this, line surveys, local sampling, and internationally accepted rock mass classification studies (RMR, Q, GSI) were performed on the rock mass outcrops, which are positioned against to the Black Sea. At the conclusion of these studies, rock mass engineering properties were determined through the utilization of empirical equations that incorporate data derived from site investigation studies and laboratory test results as input.

Correlation of Geotechnical and Mineralogical Properties of Lithomargic Clays in Uttara Kannada Region of South India

The present study explores the intricate relationship between the geotechnical and mineralogical properties of lithomargic clays in the Uttara Kannada region of south India. Lithomargic clays, characterized by their unique composition of clay minerals and calcareous content, play a crucial role in the geotechnical behavior of soils. The study aims to provide a comprehensive understanding of the interplay between the mineralogical composition and engineering characteristics of lithomargic clays, shedding light on their suitability for various construction and infrastructure projects. The research methodology involves a systematic analysis of lithomargic clay samples collected from different locations in the Uttara Kannada region. Geotechnical investigations, including particle size distribution, Atterberg limits, unconfined compressive strength (UCS), California bearing ratio (CBR) and triaxial tests, are conducted to assess the engineering properties of the clays. Concurrently, mineralogical analyses, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), are employed to identify and quantify the clay mineral constituents within the samples. The findings of this study reveal correlations between specific mineralogical features and geotechnical behaviors of lithomargic clays. Understanding these relationships is crucial for predicting the response of these clays to different engineering applications, including slope stability, foundation design and embankment construction. The research contributes valuable insights to the scientific and engineering communities, aiding in the informed utilization of lithomargic clays in geotechnical projects in the Uttara Kannada region and beyond. The outcomes of this investigation, such as the correlation of geotechnical properties with the variation in minerals in various sample locations, enhance our understanding of the complex nature of lithomargic clays, providing a foundation for more sustainable and effective engineering practices in the geologically diverse landscapes of south India.

Statistical comparative analysis between strength parameters of a bauxite mining tailing through laboratory tests and numerical simulation

Tailings dams are the primary global way to solve the problem of low storage availability for tailings resulting from mining. However, the recent ruptures of this reservoir in Brazil, such Mariana and Brumadinho dams, draw attention to the importance of studies determining the geomechanical characteristics and behavior of mining tailings. With the implementation of Law nº 14066/2020, which establishes the National Dam Safety Policy, there was an increase in demands for the monitoring and inspecting dams and the imposition of bills. Given this, triaxial tests were carried out to characterize the mechanical behavior of bauxite mining tailing from a Brazilian deposit. Confining pressure of 25, 50, 100, and 200 kPa was applied. Moreover, data were obtained for applying numerical simulation modeling based on the parameters determined for this material. Therefore, this paper describes a comparison using exploratory data analysis between the results obtained in the laboratory by the triaxial test and the results obtained by the finite element method (FEM) analysis with the aid of the Abaqus software. Statistical analysis showed a greater discrepancy between laboratory and numerical simulation results. The most significant differences observed between laboratory and numerical simulation results occurred for the lowest stress levels. The greatest differences observed between laboratory and numerical simulation results occurred for the lowest stress levels. The difference was significant also in terms of behavior. This fact highlights the need for extensive geotechnical investigation to characterize the material adequately and obtain parameters to simulate the correct tailing behavior and develop a safe design for storage structures.

Excess Pore Pressure Migration Analysis Due to High Embankment Construction – Case Study East Kalimantan

A 42-inch pipeline traverses a predominantly flat right-of-way (ROW), running from south to north in East Kalimantan. Adjacent to the ROW, a coal mine concession was located on the western side, while the Mahakam River lies a further 3 km to the east. A mining waste dump has been constructed since 2010, situated in an area underlain by soft alluvium soil (Qa). The waste was stacked, reaching heights of up to 75 meters, with its toe approximately 200 m from the edge of the ROW. In 2016, a failure occurred in the ROW, causing the 42-inch pipeline to shift a maximum of 6.8 m horizontally, and rise by 2.0 m within a 300 m span. A geotechnical investigation was then conducted, consisting of 7 CPTu with dissipation testing. The CPTu results indicated high pore pressure, with a layer of soft clay ranging from 15 to 32 m thickness found in the ROW area. A hypothesis was formulated suggesting that the soft clay was not fully consolidated. Hence, the failure of the pipeline was possibly caused by the migration of excess pore water pressure accumulated during the construction of the waste dump. Results of the investigation indicated that the permeability coefficient was 2.5 times greater in the horizontal direction compared to the vertical ones (kh/kv = 2.5), allowing the pore water pressure to migrate more easily in the horizontal direction. This study aims to elucidate how the migration of excess pore water pressure in the horizontal direction influences ground stability. The analysis was conducted using finite element software MIDAS GTS NX, with the kh/kv varying from 2.5 to 100 times to explore excess pore pressure movement behaviors. The results of this study confirm that excess pore pressure migration can occur horizontally if the horizontal permeability coefficient is larger than its vertical counterpart. Thus, this study highlights that the greater the permeability coefficient and the larger the ratio, the further the excess pore pressure travels. Moreover, the horizontal displacement increases with the permeability coefficient ratio.

Conservation-oriented integrated approach for structural stability assessment of complex historic masonry structures

The paper presents a multidisciplinary approach for diagnosing the structural stability of the Takiyya of Ibrahim al-Gulshani in Historic Cairo using geometric and architectural documentation, field survey, laboratory tests, and numerical analyses under static and seismic conditions. The Takiyya, built during the Mamluk period, is an important medieval architectural complex in Egypt and has undergone multiple renovations. The field-testing includes geotechnical and geophysical investigations to evaluate the properties of the bearing soil beneath the monument. A 3D survey using Terrestrial Laser Scanning was employed to record Takiyya’s geometry. Terrestrial photogrammetry and high-resolution images accompanied by an in-situ damage survey were used to document cracking levels, stone weathering, and identification of decay patterns. Laboratory tests were conducted to assess the mineral composition, physical and mechanical properties of the construction materials to enable structural assessments. Data appraisal and integration into architectural drawings was used for mapping degradation patterns and the preservation state of the building. The documentation procedures combined with experiments were then employed to develop a model for structural analysis. Three-dimensional finite element numerical simulations employing macro-modelling approaches were performed for the Takiyya structures under various loading conditions, including modelling the bearing soil, resulting in good agreement with in-situ recorded structure damage patterns. The static and seismic nonlinear analyses helped identify the causes and effects of the current structural deficiencies. The adopted methodologies provided large amounts of information, permitting an improved understanding of existing damage and the assessment of the preservation state of the masonry structure. This project exists thanks to the Egyptian Ministry of Tourism and Antiquities (MoTA) and is funded by World Monument Fund (WMF) through various donors.

The Queensland geotechnical database

The Queensland Geotechnical Database (QGD; qgd.org.au) was launched in October 2017 with the aim of consolidating primarily tax and toll-payer subsidised geotechnical investigation logs into an open platform. The QGD was influenced by public geotechnical databases in the United Kingdom and New Zealand, and the work of Robert Leggett in Canada as summarised in ‘Cities and Geology’ (1973). As of October 2023, the QGD includes over 3100 geotechnical investigation logs authored by over 10 public and private entities, dating back to 1966. It also includes national geological mapping and links to over 400 technical papers related to sites in Australia. This paper summarises the formation of the QGD, which emerged from the Queensland Chapter of the Australian Geomechanics Society (AGS) and originated from a personal database converted to an open format with hosting support from The Open Data Institute Australia. The QGD was later transferred to The University of Queensland and continues there in support of their Sustainable Infrastructure Research Hub (UQ SIRH). The paper explores the evolution of its formation, the legal framework in Australia regarding investigation log ownership, and the licensing scheme adopted for the database. It outlines the technical features and intended practicality of the database, and its alignment with the objectives of the UQ SIRH. The paper concludes with an outline of opportunities for conversion to a nationalised Australian Geotechnical Database and its usage for educational purposes.

Interpolation of non-stationary geo-data using Kriging with sparse representation of covariance function

Interpolation of spatially varying measurements, e.g., spatial variation of a geotechnical property along depths, is often needed in many disciplines, including geotechnical engineering. Among various interpolation methods, geostatistical methods, such as Kriging, are popular since they are able to not only provide the best estimates but also quantify the interpolated uncertainty. However, Kriging relies on an assumption of data stationarity, and a transformation from non-stationary data to stationary data by, e.g., detrending, is required when using Kriging to interpolate non-stationary data. Detrending, however, is a tricky and long-lasting challenge in geo-data analyses. To tackle this challenge, this study develops a novel Kriging method for direct interpolation of spatially non-stationary data without detrending. A sparse representation of covariance function is proposed for Kriging interpolation of spatially non-stationary data, bypassing the tricky detrending process. The proposed Kriging method is particularly appealing for non-stationary geotechnical site investigation data often encountered in geotechnical practice (e.g., spatial variation of soil properties over different soil layers along depth). Equations are derived for the proposed Kriging method, and it is illustrated and validated using numerical examples. Results show that the proposed Kriging method with sparse representation of covariance function is directly applicable to spatially non-stationary data and has the advantages of improved accuracy and reduced interpolation uncertainty when interpolating spatially varying, non-stationary data.

Stabilization of Shallow Landslides Induced by Rainwater Infiltration—A Case Study from Northern Croatia

Climate change brings with it phenomena such as large amounts of rainfall in short periods. Infiltration of rainwater into clayey soils is a common trigger for shallow landslides on slopes. In this way, numerous shallow landslides occur in the area of northern Croatia, and a characteristic example is the landslide “Orehovčak”. To stop the sliding of the destabilized slope, it was necessary to solve the drainage of water that infiltrates the landslide body. For this purpose, detailed geotechnical investigations and monitoring were conducted. Many data were collected at the investigation site, especially soil characteristics and groundwater fluctuations. The surface soil on the slope consists of highly plastic clay, and the sliding surface was created in contact with the solid subsoil of marl, the depth of which varies positionally. The analyses confirmed that water is a slip trigger. To solve the problem, excavations and installation of deep drains were performed. The slope safety factor confirms landslide stabilization, whose calculated value after rehabilitation was Fs = 1.645. Inclinometer readings carried out after remediation show that slope slippage stopped. This confirms that the presented remediation method is very applicable to shallow landslides in northern Croatia and similar landslides around the world.

Feature analysis of precipitation-induced subgrade defects on a high-speed rail ballasted track using multiple track inspection data: A case study

Heavy rainfall has posed a great challenge to the service performance of high-speed rail (HSR) substructure, resulting in a reduction in the ride quality and safety of high-speed trains. To carry out proper repair work for the substructure, it is imperative to realize efficient identification of precipitation-induced subgrade defects. To this end, this paper aims to extract the features of typical precipitation-induced subgrade defects from the multiple track inspection data to provide a basis for defect identification. Firstly, the geotechnical site investigation including Ground Penetrating Radar (GPR) detection, moisture content test, and dynamic cone penetration (DCP) test of a typical defective spot is performed to determine the condition of the subgrade after heavy rainfall; then, the analysis methods of track inspection data are introduced; finally, the track geometry data and carbody acceleration data of four typical defective sections are analyzed, and the time-domain, frequency-domain and discrete wavelet transform (DWT)-based features which are highly correlated with the precipitation-induced subgrade defects are extracted. The results show that the feature indexes extracted from track surface irregularity and carbody vertical acceleration increase significantly after heavy rainfall; the long wavelength components (8 m and above) of both track irregularity and carbody vibration are more sensitive to the subgrade defects, which is reflected by the sharp increase of the DWT-based features at some levels corresponding to long wavelength ranges. The results of defect feature extraction based on the track inspection data agree well with the geotechnical site investigation results, which demonstrate the feasibility of utilizing multiple track inspection data to identify the typical precipitation-induced subgrade defects.

Geophysical and Geotechnical Investigations of the Subsurface for Construction Purposes at Federal College of Education Osiele, Abeokuta, Southwestern Nigeria

Knowledge of the surface and subsurface structures are vital for construction procedures. Integrated geophysical and geotechnical methods were applied to image the subsurface for evaluation of the stratigraphy and the competency of each geoelectric layer for construction purposes at the Federal College of Education Osiele, Abeokuta South-western Nigeria. Nine Vertical Electrical Sounding (VES) using Schlumberger electrode configurations were conducted over a current electrode spacing of 200 m. Multi-channel Analysis Surface Wave (MASW) was the seismic technique used for the geotechnical analysis of the study area and laboratory analysis was performed to investigate, Atterberg limit, particle size distribution, compaction test, specific gravity, and California bearing ratio. Results from the geophysical investigation revealed four to five geoelectric layers: topsoil, clayey sand, sandy clay, laterite, and fresh basement. The MASW results have s-wave velocities range of 40–500 m/s and analysis showed four layers. The laboratory analysis revealed that all the ten traverses have specific gravity, which is out of limit except sample 8 which is 2.80, plastic index and Atterberg limits of liquid were within permissible values of 12% and 35% respectively except samples 9 and 10, and California Bearing Ratio within specified limits. Geophysical and geotechnical investigation of the subsurface carried out in the study area for construction purposes revealed that the foundation of a heavy structure should be targeted at around 20 m into the subsurface.

Back analysis of cohesion and friction angle of failed slopes using probabilistic approach: two case studies

In general, geotechnical investigations deal with the back analysis of the geotechnical parameters on the basis of the field observation. According to the back analysis method introduced in the present study, geometry of a number of failed slopes have been carefully mapped and then statistical features of the groundwater level, the bulk unit weight and other measurable parameters have been determined. After that, a series of two-dimensional models for back analysis of the failures have been established. Moreover, statistical analyses based on probabilistic approaches have been utilized to estimate the variation ranges of the shear strength variables. The study provided the probabilistic back analysis of the slope failure with the two case studies in the copper mines of Anjerd and Daraloo. Results indicated that the approach to the probabilistic back analysis has been effective in the analysis of the slope failures wherein considerable uncertainty has been observed in the shear strength and other influential variables. Furthermore, the probabilistic back analysis presented a lot of information in comparison to the approach to the deterministic back analysis and thus had more reasonable matching with the practice of geotechnical engineering in the real world. Therefore, this method would be beneficial and practical for stability analysis, redesigning the slopes, designing the new slopes under the same geotechnical conditions and promote the construction safety. The probabilistic back analysis could be also used to estimate the shear parameters and analyze the stability of slopes as a cost-effective and high reliability method.

Destructive impact of successive high magnitude earthquakes occurred in Türkiye’s Kahramanmaraş on February 6, 2023

AbstractTwo successive earthquakes with moment magnitudes of Mw = 7.7 (focal depth = 8.6 km) and Mw = 7.6 (focal depth = 7 km) occurred approximately within 9 h on February 6, 2023, in Türkiye, respectively. The epicenters were the Pazarcık and Elbistan districts of Kahramanmaraş. Both earthquakes occurred in the East Anatolian Fault Zone, one of Türkiye’s two major active fault systems. Between these two severe earthquakes, there was one more big aftershock with a moment magnitude of 6.6, the epicenter of which was in the Nurdağı District of Gaziantep. Then, on February 20, 2023, another aftershock earthquake with a magnitude of Mw = 6.4 occurred in Yayladağı district of Hatay. As a result of the earthquakes, severe damage occurred in several provinces and districts with a population of around 15 million, and more than 50,000 people have lost their lives. This study presents on-site geotechnical and structural investigations by a team of researchers after the Kahramanmaraş earthquakes. It summarizes the performance of the building environments as a result of on-site assessments, taking into account observed structural damage, local site conditions, and strong ground motion data. The possible causes of the observed damage are addressed in detail. These earthquakes once again revealed the common deficiencies of existing reinforced concrete structures in Türkiye, such as poor material quality, poor workmanship, unsuitability of reinforcement detailing, and inadequate earthquake-resistant construction techniques. Precast concrete and masonry structures in the region were also severely damaged during the earthquakes due to insufficient engineering service, poor materials, deficiencies during construction, etc.

Sinkhole stability chart for geotechnical investigation

Sinkholes are a common geohazard in karst areas where soluble carbonate bedrock is present. Active groundwater flow causes internal soil erosion that creates cavities in the overburden soil layer. The subsurface cavity propagates upward due to the continuous erosion process, and ultimately, they reach to the ground surface, resulting in a sudden collapse. This cover-collapse type is generally a sudden event, particularly in the area where a thick cohesive soil layer is embedded. In this study, a sinkhole stability chart was developed to quantitatively evaluate the safety against the collapse-type sinkhole. Finite-element (FE) modeling was used to simulate the collapse of sinkhole. Field testing data collected from multiple sinkhole sites were used as input to the FE model. To simulate the progress of sinkhole activity, a number of different scenarios with varied size of cavity, strength of overburden soil were simulated, and the corresponding safety factors were determined. Even though each site has varied soil profile, a general trend of the safety factor was observed. The envelopes of safety factors (or equal-safety lines) were statistically determined by using a multivariate regression method. The chart that quantitatively evaluate the stability of sinkhole is used as a decision-making tool for further engineering investigation or mitigation.

Drone as a tool for geotechnical investigation

Natural slopes are naturally exposed to instability due to accidents involving landslides and erosion. In general, access to these areas is difficult due to the uneven profile and inconsistency of the terrain, presenting a risk of accidents. However, for a careful assessment of the level of geological risk to which the slopes are subjected, accurate and detailed topographic and photographic surveys are necessary. In this sense, drone mapping has proven to be an effective tool, as it allows obtaining digital topographic maps supported by photographic documentation in excellent resolution, allowing the identification of the geological features of the surveyed areas. The Mackenzie School of Engineering in partnership with the Francisco Morato city hall carried out a geotechnical investigation and topographic record through photointerpretation of slopes in an advanced process of erosion. As mapping products, the following were generated: the Digital Surface Model (DSM), the Digital Terrain Model (DTM), the 3D Model (mesh), the photo orthomosaic and the contour lines, among others. The detailed evaluation of these products will enable the elaboration of a recovery project for the area.

Geophysical and geotechnical investigations of the site of a collapsed two-storey building in Modomo, Ile-Ife, Southwestern Nigeria

Geophysical and the geotechnical methods were used to study the site of a collapsed two-storey building in orderto determine the sequence and competence of the subsurface layers and determine the cause of the collapse of the building. The geophysical method employed the electrical resistivity method involving one dimensional (1D) Vertical Electrical Sounding (VES) and the two dimensional (2D) imaging techniques. Three VES stations were occupied using Schlumberger electrode configuration. 2D imaging data were acquired along four traverses using dipole-dipole electrode configuration. The geotechnical method involved Cone Penetration Test (CPT). CPT data was acquired at two points with the aid of 2.5 ton Dutch CPT machine. The results showed four subsurface layers based on the 1D VES results and 2D imaging results namely: topsoil, weathered layer, fractured basement rock and fresh basement rock. The topsoil resistivity varied from 116 Ωm to 191 Ωm and has thickness of about 1.5 m. It was classified as moderately competent. The second layer is weathered rock with resistivity varying between 92 Ωm and 327 Ωm and of about 8 m to 13 m thickness. This layer is also moderately competent. The third layer is fractured basement rock. It underlies the weathered rock and have resistivity varying from 391 Ωm to 405 Ωm. Its thickness varied from about 2 m to 20 m. This layer is competent. The fourth layer is the fresh basement rock having resistivity varying from 1365 Ωm to 12348 Ωm and is highly competent. The subsurface materials in the area are competent and can sustain the foundation of the building. Hence, the study concluded that the building collapse did not result from incompetent subsurface materials. Factors other than incompetent subsoil material that is human factors are believed to be responsible. This study has demonstrated the effectiveness of geophysical and geotechnical investigations in determining the competence of subsurface materials at engineering sites.

Optimizing Terrain Classification Methods for the Determination of Bedrock Depth and the Average Shear Wave Velocity of Soil

The advancement of remote sensing has enabled the creation of high-resolution Digital Elevation Models (DEMs). Topographic features such as slope gradient (SG), local convexity (LC), and surface texture (ST), derived from DEMs, are related to subsurface geological conditions. In South Korea, bedrock depth (Dbedrock) and the average shear wave velocity of soil (VSsoil) serve as metrics for determining the site class, which represents the degree of site amplification in seismic design criteria. These metrics, typically measured through geotechnical and geophysical investigations, require predictive methods for preliminary estimation over large areas. Previous studies developed an automatic terrain classification (AC) scheme using SG, LC, and ST, and subsequent research revealed that terrain classification effectively represents subsurface conditions such as Dbedrcok and average shear wave velocity down to 30 m depth. However, AC intrinsically depends on the regional features of DEMs, dividing regions based on nested means of topographic features (SG, LC, and ST). In this study, we developed two terrain classification methods to determine the thresholds of class divisions, aiming to optimize Dbedrock and VSsoil predictions: Sequentially Optimized Classification (SOC) and Non-Sequentially Optimized Classification (NOC). Through the study of the sensitivity of terrain classification methods, smoothing levels, and threshold levels for terrain class generation, we identified the best classification method by comparing it with the geological and mountainous region distribution. Subsequently, we developed DEM-dependent regression models for each class to enhance the accuracy of predicting Dbedrock and VSsoil. The main findings of this study are: (1) the terrain class map suggested in this study represents the distribution of alluvial plane and mountainous regions well, and (2) the DEM calibration for each class provides increased accuracy of Dbedrock and VSsoil predictions in South Korea. We anticipate that the terrain class map, along with Dbedrock and VSsoil maps, will be effectively utilized in geological interpretations and land-use planning for seismic design.

Investigating stone column effectiveness for sabkha soil improvement: field tests and numerical model

This study explores the application of stone columns to improve the bearing capacity of sabkha soil for the construction of a Lattice Communication Tower foundation in the Eastern Province of Saudi Arabia. Geotechnical investigation report, an on-site footing loading test to evaluate the foundation's bearing capacity and settlement behavior following stone column installation, and post-cone penetration tests (CPT) to assess soil densification are all part of the study data. The uppermost 4 m of the soil profile comprise a medium to dense layer of sand with silt, followed by a 12-m layer of weak sabkha soil (SPT, N less than 4). Below the sabkha layer, the strata exhibit varying densities, ranging from medium to dense and very dense layers, extending to the maximum depth of investigation. The comparison of Pre- and Post-CPT data revealed significant improvements in the sand and silt layer above the sabkha layer, as well as moderate improvements in the upper portion of the sabkha layer. However, the majority of the sabkha soils and underlying soil layers did not show significant improvement. Plaxis 3D numerical models were employed to provide insights into the performance of the composite area encompassing stone columns and the surrounding soil. Comparing field tests and numerical models showed that neglecting stone column installation effects in numerical models led to overestimating settlements. However, when examining the field data and numerical results with a raised coefficient of lateral earth pressure when of K∘=2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{^\\circ }=2$$\\end{document}, a distinct alignment between settlement values consistent with those derived from field testing. The findings highlight the importance of including site-specific conditions and installation effects in numerical modeling to accurately predict the behavior of stone columns in sabkha soils.

Cyclic resistance evaluation of marine clay based on CPTu data: a case study of Shaba Wind Farm

The offshore wind farm industry has recently experienced significant global growth. This study presents a thorough site investigation and analysis of the cyclic resistance of marine clay for offshore foundation design, using the Shaba wind farm in southern China as a case study. In-situ cone penetrometer (CPTu) tests and borehole sampling are conducted to explore the geotechnical characteristics of the soils. However, the soil conditions are characterized by multiple layers and complex sedimentary components. The classification and mechanical properties, such as water content and cyclic resistances, are compared through CPTu interpretation and laboratory tests. The findings indicated that a single physical indicator cannot determine cyclic resistance. In addition, the well-established method in existing literature proved unsuitable for marine clay. Consequently, multiple regression analysis shows that a linear relationship exist between cyclic resistance and depth-corrected CPTu index [EXP(qE/fs)0.3/H], hence a new evaluation method is developed to predict the cyclic resistance of marine clay based on CPTu data. This research aims to provide more reliable guidance for geotechnical investigations, supporting the rapid expansion of offshore wind farms.

Correlation Analysis and Prediction of the Physical and Mechanical Properties of Coastal Soft Soil in the Jiangdong New District, Haikou, China

The compressibility and shear strength of soil play a crucial role in engineering design and construction. For this study, samples were collected from the indoor geotechnical tests conducted on the fourth layer of the third series of the Haikou Formation. By conducting a correlation analysis of various physical properties of soil and utilizing the random forest algorithm, we developed a predictive model for the compressibility and shear strength of coastal soft soil. Initially, we proposed an empirical formula that utilizes mathematical statistical analysis methods to characterize the correlation between the indicators of this soil. Subsequently, we employed the feature selection guided by the aforementioned data analysis results to establish a random forest model. This model predicts the compressive modulus, compressibility coefficient, cohesion, and internal friction angle of the soil. The results indicate that the established model exhibits strong predictive capabilities, with the mean squared error values of compression modulus (0.012), compression coefficient (1.21× 10−6), cohesion (0.081), and internal friction angle (0.003). The data analysis methods, fitting parameters, empirical formulas, and random forest model employed in this study hold substantial value in guiding the preliminary evaluation stage of engineering projects with limited data. This study helps to save time and cost of geotechnical investigation for soft soils in the area.