Geotechnical Design Parameters Research Articles

Determination of soil parameters using in situ soil testing for the design of highway

Determination of soil parameters of any soil is very important before executing highway construction as it gives detailed information of the soil and its various properties which will be useful in the design of the pavement. The paper discusses determination of soil parameters of the ongoing construction work, which includes grain size analysis, consistency test, compaction test, 4 day soaked CBR at 3 energy levels, and field details. Boreholes drilling was done using augers. Using rotary diamond (core) drilling equipment, cores were drilled into the bedrock, and bedrock core samples are then extracted from the cores. Test pits were excavated with hydraulic excavators. This paper summarizes the different geotechnical design parameters for the subsurface conditions at the site to support the highways. A review of rotary drilling and rock coring in terms of the correct handling, transportation, and storage of soil and rock samples in preparation for laboratory testing is also given.

Geotechnical site characterization by DMT and laboratory tests on an unsaturated tropical soil site for slope stability analysis

The slope stability is an important topic because it presents risks of socio-economic losses caused by eventual ruptures. It is necessary to identify the site profile, as well as obtaining soil strength parameters for the slope stability analysis. This paper presents and discusses the use of the Flat Dilatometer Test (DMT) in the geotechnical site characterization for slope stability analysis in an unsaturated tropical soil site. Six DMTs were performed to define the stratigraphical profile and estimate geotechnical parameters. Shear strength parameters were determined in the laboratory using saturated and unsaturated triaxial compression as well as soil water retention curves (SWRC) to support DMT data interpretation. A commercial software was used to perform the slope stability analysis a cut slope with 6.6 m height and a gradient around 55° to illustrate the application of DMT and triaxial test data. The DMT allowed the representative site profile to be identified, as well as estimating the design parameters that compared well to those interpreted from unsaturated triaxial test data for the in-situ soil suction. The DMT can be used as logging test in the preliminary characterization of studied site specially to define the stratigraphical profile, site variability, select the regions to collect disturbed and undisturbed soil samples and as the first attempt to estimate the geotechnical design parameters via correlations. It is important to emphasize that laboratory tests on undisturbed soil samples are essential in the slope stability analysis of unsaturated tropical soil profiles.

Efficacy of Several Design Methods for Predicting the Axial Compressive Capacity of Piles

A variety of design methods for determining piles’ axial compressive load capacity are routinely employed in current practice. These range from methods specified in building codes to proprietary methods developed and employed by an assortment of engineering firms. In this study, the performance of eight commonly used design methods was evaluated using a database of 505 load tests and associated geotechnical design parameters compiled from Professor Olson’s database and that of the Iowa State Department of Transportation. The methods investigated included standard penetration test (SPT)-based methods, such as those recommended by the Federal Highway Administration (FHWA), U.S. Army Corps of Engineers, American Petroleum Institute, and Revised Lambda; and cone penetration test (CPT)-based methods such as those recommended by the Norwegian Geotechnical Institute, Imperial College, Fugro, and University of Western Australia. Pile capacities were calculated using APILE software and were compared with the measured capacities interpreted using the standard Davisson criterion and stored in the databases. The performance of all design methods was evaluated in relation to accuracy, precision, effect of soil type, diameter, and length. Both SPT and CPT methods exhibited similar accuracies, however, CPT-based design methods exhibited significantly better precision compared with SPT-based methods. All methods had shortcomings and appeared to work best under certain conditions, which are documented in this paper. The authors believe that this evaluation will permit practicing engineers and regulating bodies to better understand the efficacy of various design approaches in common use.

Advanced monitoring of tailings dam performance using seismic noise and stress models

Tailings dams retain the waste by-products of mining operations and are among the world’s largest engineered structures. Recent tailings dam failures highlight important gaps in current monitoring methods. Here we demonstrate how ambient noise interferometry can be applied to monitor dam performance at an active tailings dam using a geophone array. Seismic velocity changes of less than 1% correlate strongly with water level changes at the adjacent tailings pond. We implement a power-law relationship between effective stress and shear wave velocity, using the pond level recordings with shear wave velocity profiles obtained from cone penetration tests to model changes in shear wave velocities. The resulting one-dimensional model shows good agreement with the seismic velocity changes. As shear wave velocity provides a direct measure of soil stiffness and can be used to infer numerous other geotechnical design parameters, this method provides important advances in understanding changes in dam performance over time.

Optimization of Sand-Bentonite Mixture for the Stable Engineered Barriers using Desirability Optimization Methodology: A Macro-Micro-Evaluation

In this paper, Desirability Optimization Methodology (DOM) is employed to achieve optimum sand bentonite mixture (SBM) based on multiple antagonist macro-geotechnical responses of the compacted SBM prepared using poorly graded sand with the mean grain size around 0.2 mm and bentonite with plasticity index around 157% for the stable engineered barriers (EBs). For this purpose, varying mix designs of SBM compacted at compaction energy of 2,700 kN-m/m3 are initially tested to determine their mechanical properties, volumetric-change behavior, and hydraulic conductivity. The unconfined compressive strength, cohesion, angle of internal fiction, swell pressure, compression index, and hydraulic conductivity are taken as the geotechnical design parameters for the SBM. Mathematical models are developed and statistically validated for these design parameters using sand content (SC) and bentonite content (BC) as the predictors. In addition, models are also developed to predict compression curves for compacted SBMs. Moreover, microstructural evaluation is conducted through scanning electron microscope (SEM) analysis to determine the SBM having a desirable microstructure for stable EB. It is observed that a major shift in the microstructure from medium pores to micro-pores occurs for the BC between 20% and 30%. Afterward, optimization of SBM is carried out by integrating developed models for the geotechnical design parameters in a desirability function (D) algorithm, which is subsequently simulated by setting maximization of strength and minimization of swell pressure, compressibility and hydraulic conductivity of compacted SBM as the goals. A reasonably high D-value is achieved for the SBMs having SC:BC in a range of 74:26 to 78:22 with the highest at 75.63:24.37 against the set goals. This study manifests an effective and pragmatic strategy for designing the SBM for a stable EB considering its antagonist hydraulic, volumetric change, and mechanical responses.

Geotechnical RBDO: Coupling the inverse reliability algorithm with multi-objective reliability-based design optimization of geotechnical systems

The analysis and design of geotechnical engineering inevitably deal with various sources of uncertainties. To further expand the application of reliability methods in geotechnical engineering design works, the inverse reliability algorithm is modified to incorporate unknown geotechnical design parameters in this paper. Based on the established HLRF algorithm for first order reliability analysis, the proposed approach can easily realize traditional single-objective inverse reliability-based design (RBD). Further, the multi-objective inverse reliability design is achieved by combining several single-objective inverse reliability analysis modules through a coupling matrix without seeking for any other surrogate functions. The Nataf transformation is integrated into the method to deal with the correlation of random variables. In addition, the algorithm can be combined with any nonlinear optimization method when the number of design parameters is greater than the number of performance functions, at which point the RBD is extended to reliability-based design optimization (RBDO) with an objective function related to the optimum design purpose. Verifications of the proposed approach are illustrated through several examples, which show that the proposed reliability design optimization framework is effective and can be used as a basic tool for RBDO problems in geotechnical engineering.

Yielding and K 0 Value Variation of Cemented Sand along a K 0 Path

The yield stress and the coefficient of lateral earth pressure at rest, K0, of soil are important parameters for geotechnical design. However, the effect of cementation on the values of yield stress and K0 of artificially cemented sand along a K0 path has not been fully studied, despite the common use of cement mixing for soil improvement. A series of consolidation tests of K0 on artificially cemented sand has been conducted using a plane-strain apparatus. The test results show that the value of K0 of cemented sand is very much affected by the amount of cementation; the lowest value of K0 in a K0 test corresponds to the yield stress provided by cementation. It is established in this study that the yield stress of cemented sand marks the start of a large amount of bond destruction. The value of K0 reduces exponentially with the increase in cement content. One important practical implication is that the lateral earth pressure at rest can be reduced by introducing cementation to soil. This study also shows that Jaky’s equation is no longer applicable for estimating the value of K0 of cemented sand, although it may still provide a rough estimate for clean sand. The value of K0 of cemented sand can be estimated using a combination of Jaky’s equation for clean sand and Jaky’s equation for cement content.

A Fully-Self-Adaptive Harmony Search GMDH-Type Neural Network Algorithm to Estimate Shear-Wave Velocity in Porous Media

Shear wave velocity (VS) is one of the most important parameters in deep and surface studies and the estimation of geotechnical design parameters. This parameter is widely utilized to determine permeability and porosity, lithology, rock mechanical parameters, and fracture assessment. However, measuring this important parameter is either impossible or difficult due to the challenges related to horizontal and deviation wells or the difficulty in reaching cores. Artificial Intelligence (AI) techniques, especially Machine Learning (ML), have emerged as efficient approaches for dealing with such challenges. Therefore, considering the advantage of the ML, the current research proposes a novel Fully-Self-Adaptive Harmony Search—Group Method of Data Handling (GMDH)-type neural network, named FSHS-GMDH, to estimate the VS parameter. In this way, the Harmony Memory Consideration Rate (HMCR) and Pitch Adjustment Rate (PAR) parameters are calculated automatically. A novel method is also introduced to adjust the value of the Bandwidth (BW) parameter based on the cosine wave and each decision variable values. In addition, a variable-size harmony memory is proposed to enhance both the diversification and intensification. Our proposed FSHS-GMDH algorithm quickly explores the problem space and exploits the best regions at the late iterations. This algorithm allows for the training of the prediction model based on the P-wave velocity (VP) and the bulk density of rock (RHOB). Applying the proposed algorithm to a carbonate petroleum reservoir in the Persian Gulf demonstrates that it is capable of accurately estimating the VS parameter better than state-of-the-art machine learning methods in terms of the coefficient of determination (R2), Mean Square Error (MSE), and Root Mean Square Error (RMSE).

A Practical Approach To Bridge Foundation Design

This paper aims to provide guidance on a process for the design of bridge foundations. It sets out a brief explanation of bridge terminology, and afterwards discusses aspects of the geotechnical investigation, foundation design, and construction specification for bridges. It is intended to assist engineers who may not be familiar with bridge design in gaining a working knowledge of the basic design principles and requirements. It is not intended as a detailed step-by-step procedure for foundation design itself, but rather as a framework for a systematic process of design. Among the aspects that are emphasized are the process of assessment of geotechnical design parameters, and the means by which the outputs from geotechnical analyses can be most effectively communicated to others involved in the design process, especially the structural engineers.

Engineering approaches for road construction projects and determination of geotechnical design parameters: Road network improvement of Northern Iraq

Transport in Northern Iraq become an important issue in terms of trading due to its geographical position. Road construction between Darbandikhan and Kalar villages in the northern part of Iraq is crucial for the connection of Erbil and Suleymaniye to northeast. The planned road construction requires a detailed environmental and geotechnical study in order to determine geo-engineering parameters of ground conditions. For this purpose this study is carried out to highlight the engineering geological and geotechnical features considering the groundwater conditions of the Darbandikhan - Kalar Road route section. In this context, field and laboratory works were performed along the projected route. Within the scope of field studies, an engineering geology map was generated, a suitable routing was specified and drilling and in-situ testing was completed. Seven boreholes and total 196,5 m geotechnical purposed drilling works performed along the planned route section. The core samples obtained from drilling works are utilized for laboratory testing. As a result of this study information about the bearing capacity, slope stability and basic soil parameters were determined and no problems were encountered.

Integrating uncertainty into geotechnical design of underground openings in tectonically undisturbed but lithologically varied sedimentary environments

A systematic but straightforward probabilistic approach was adopted for the preliminary design using a tunnel case in Egnatia Odos Highway. This tunnel was excavated in a heterogenous molassic formation in Northern Greece, and more specifically in tectonically undisturbed but lithologically varied sedimentary series. This research aimed to identify sources of uncertainty and evaluate its governance during the selection of the geotechnical design parameters. Rigorous analyses of the critical parameters and factors were undertaken following a standardised method for designing underground structures based on the probability theory. Initially, the statistical analysis of the intact rock strength parameters and project-specific geological and geotechnical factors allowed the development of understanding in determining these sources of uncertainty and assisted in quantifying them. The lithological units encountered in the tunnel alignment were classified into first, Geological Units and, secondly, into Rock Mass Types (Geotechnical Units). Finally, the latter were grouped into anticipated Rock Mass Behaviour Types, which were numerically investigated using RS2 for the Finite Element Method analysis and Unwedge to assess these Rock Mass Types' failure modes. For this purpose, the Point Estimate Method was used in the FEM analysis to evaluate the effect of uncertainty in the strength parameters. Ultimately, the numerical analysis results subsequently led to the preliminary design of the respective support sections. Although this investigation was limited by the geotechnical information provided, it was concluded that the approach followed proved to be adequate in identifying the primary sources of uncertainty and its impact on geotechnical design. It was also noted that with more detailed geological information, this probabilistic approach could be used to produce a robust final support tunnel design.

Estimating the Small Strain Stiffness of Peat Soil Using Geophysical Methods

Geotechnical design commonly requires that the in-situ stiffness, strength and permeability of the ground be obtained. Laboratory based investigation often related with risk of sample disturbance and difficulties to replicate the in-situ stress condition which results in overestimation or underestimation. Application of geophysical methods in geotechnical investigation previously was limited to targeting and dimensioning sub-surface features due to lack of resolution. However, rapid developments of geophysical methods result in the application of these methods in providing geotechnical design parameters. Multichannel analysis of surface waves (MASW) and seismic refraction were among the geophysical methods capable of obtaining stiffness parameters including the maximum shear modulus (Gmax) and maximum elastic modulus (Emax). The study revealed the efficiency of these methods to measure the small strain stiffness of peat soil with high accuracy as the results obtained were found to be similar to those obtained by previous researchers. Overall, the Gmax and Emax values of peat soil obtained range from 0.49 to 1.72 MPa and 1.46 to 5.15 MPa respectively. The Gmax and Emax values obtained shows significant increase with depth governed primarily by the effective stress. Other parameters such as degree of decomposition and peat thickness also shows potential influence on the Gmax and Emax values obtained.

Application of Boosting-Based Ensemble Learning Method for the Prediction of Compression Index

Obtaining geotechnical design parameters by conducting in situ or laboratory testing has always been challenging because of difficulty involved with handling, transportation, release of overburden pressure and poor laboratory conditions. Engineers thus depend on empiricism. Over the decades, many empirical correlations have been proposed to relate index properties of soils with geotechnical design parameters. Conventionally, regression-based methods have been applied to build these empirical relationships. These models though simple, often are not flexible enough to capture more complex relationships between the dependent and the independent variables. Also adding the right interaction terms or polynomials can be tricky and time-consuming. In recent years, advances in the field of data mining have produced robust and efficient ensemble machine learning algorithms like boosting methods, which not only can learn nonlinear relationships but also have strong boundaries in terms of generalization performance. However, boosting methods are yet to be used in regression problems in the field of geotechnical engineering. In this paper, a recently developed boosting method called extra gradient boosting method (XGBoost) is applied to predict the compression index of normally consolidated soils. An efficient grid search algorithm in combination with a three-way hold out technique is used to tune the hyperparameters of the XGBoost algorithm. This study suggests that application of XGBoost in combination with the grid search technique leads to an improvement of 8–11% in prediction accuracies compared to published results that used single- and multi-variable regression, artificial neural network for prediction of compression index. Consequently, XGBoost has potential applicability in estimation of soil properties.

Compressibility Behaviour of Peat Reinforced with Single and Multiple Deep Soil Mixing (DSM) Columns

Peat represents an extreme form of soft soil and it poses serious problems in construction due to its long-term consolidation settlement even when subjected to a moderate load. Hence, suitable geotechnical design parameters and construction techniques are needed for this type of ground condition. Deep soil mixing (DSM) method is one of the widely used chemical methods of ground improvement for soft clay. However, DSM technique is quiet new for peat. Hence, aim of this research was to study the compressibility behaviour of peat stabilized with fly ash using DSM technique. A series of Rowe Cell consolidation experiments was conducted on peat and peat stabilized with fly ash. For the stabilization, 50% of fly ash was added to peat and single and multiple deep mixing columns were formed. Based on the outcome of this research, it was noticed that compressibility parameters such as compression index (Cc) and swell index (Cs) reduce with the addition of fly ash. Percentage reductions in Cc by the addition of stabilized single and multiple columns (for column area ratio of 16%) were 27.3% and 39.4% respectively compared to raw peat, while the reductions in Cs were 37.6% and 62.5% respectively for single and multiple columns. In addition, it was noticed that shear strength parameters of peat (c' and φ') can be significantly improved by stabilizing with fly ash. On the whole, DSM technique is applicable for peat, and for a given area ratio, multiple DSM columns are more effective in reducing the compressibility compared to asingle DSM column.

Assessment of Skempton's pore water pressure parameters B and A using a high-capacity tensiometer

Saturation of soils is a prerequisite in many laboratory tests involving consolidation, permeability and stress–strain behaviour. The saturation process is usually time consuming, particularly in clay-rich soils, and this can incur substantial cost and potential delays in reporting findings. The saturation of samples is assessed using the well-established Skempton's pore water pressure parameter B. In a situation where the soil is fully saturated, the B-value is approximately one. It is often the case that fine soil samples extracted from the ground, particularly those from below the water table, remain saturated. However, current testing protocols require evidence to verify a complete saturation prior to subsequent laboratory investigations. This paper reports experimental results exploring the hypothesis that, if the sample is ‘perceived’ to be saturated, then further saturation procedures may not be necessary to obtain reliable geotechnical parameters. Laboratory investigations were conducted on three different clays (kaolin clay, Belfast clay and Oxford clay) in a testing chamber instrumented with a high-capacity tensiometer. The confining pressures were applied in a ramped fashion under undrained conditions. The response of the tensiometer confirmed that the samples were saturated from the very beginning of the loading process, as implied by the B-value being close to one. Further supplementary investigations were carried out to assess the Skempton's pore water pressure parameter A and the stress–strain behaviour of the soils. The combined finding provides further evidence to suggest that the saturation process as suggested in standards may not be necessary for fine-grained soils to establish reliable geotechnical design parameters.

Variability and Bias in Undrained Shear Strength from Different Sampling and Testing Methods

AbstractUndrained shear strength is one of the most commonly used geotechnical design parameters for fine-grained soils. Disturbance produced during boring, sampling, and testing introduces an ofte...

Design adaptations in a large and deep urban excavation: Case study

In this paper, design, re-design, and performance of a long-standing very deep excavation, which was originally planned to depth of 38 m, are presented. Over-digging was not planned in the original design, thus the reassessment was performed. Two main topics were followed: deepening to increase the maximum depth of an existent excavation from 38 m to 42.5 m, and feasibility for upgrading a predesigned support system from temporary to permanent support system. The geological investigations in the project site illustrated a type of stiff and cemented coarse-grained alluvium. An observational approach with additional geotechnical investigations and in situ tests was applied. Back analyses of stability of an unsupported access ramp, as well as deformation monitoring of walls, were used in order to review geotechnical design parameters that represent the full-scale behavior of the ground. Additional nails and soldier piles together with building mat foundation were implemented as a complementary lateral support in the retaining system. From an engineering point of view, by assuming a corrosion rate of 0.065 mm/a for existent rebars, according to chemical and electrical resistivity tests, the long-term performance of the revised retaining system was verified by static and pseudo-dynamic ultimate limit state analyses. Performance monitoring during the construction shows that the measured deformation is in the lower limit of the prediction.

Geotechnical design parameter evaluation using the alluvial plain characteristics in southeastern Iraq

Geotechnical construction is responsible for the overall stability of superstructures, and if there are design errors, the structure will be exposed to potential problems. Geotechnical design starts with the correct interpretation of the target ground. Southeastern Iraq is mainly comprised of an alluvial plain with diverse geological features, and, therefore, geotechnical design requires a detailed interpretation and understanding of the area. This paper reports on laboratory and field tests and in-depth analyses conducted on these alluvial plains. The results reveal that the upper layer of this area is highly over-consolidated. This may have been caused by the removal of overburden pressure as a result of glaciation and desiccation. The highly over-consolidated soils caused considerable sample disturbance by swelling the bored sample; this provided less reliable results. However, the cone penetration test was regarded as the most appropriate field assessment method for deriving sensible geotechnical design parameters. Despite its limitations in clayey soils, the standard penetration test provided results that matched well with previous observations due to the high penetration resistance of the highly over-consolidated ground. Down-hole tests and plate load tests were considered less reliable methods due to their limited applicability in this area. This study considers geographical features, laboratory methods, and empirical correlations from in situ tests, and, therefore, provides a well-summarized guideline to evaluate special geotechnical characteristics of the alluvial plain in southeastern Iraq.

Strength and Dynamic Properties of Cement-Mixed Korean Marine Clays

Deep Cement Mixing (DCM) is the most commonly employed ground improvement method for offshore construction purposes worldwide. Nevertheless, the dynamic behavior of cement-mixed and stabilized clays is almost unknown due to the lack of experimental studies, while seismic concerns regarding offshore structures related to typhoons, tsunamis, or earthquakes are becoming more important. Moreover, very few geotechnical evaluations have been performed to characterize cement-mixed Korean marine clays, while DCM is the most commonly used practical implementation method for soft soil improvement in Korea. In this study, a series of laboratory experimental studies were conducted to obtain the static strengthening and dynamic behaviors and geotechnical engineering design parameters of cement-treated Korean marine clays. The unconfined compressive strength and shear stiffness (G) of cement-mixed Korean marine clay increase with curing time, while different trends were observed for straindependent behaviors (i.e. normalized shear modulus and damping ratio) depending on curing time and binder contents. The static and dynamic geotechnical properties and relationships of DCM treated soft clays obtained in this study are expected to be accepted for seismic considerations and designs of DCM-treated soft clays.

Geotechnical and Minerology Properties of Marine Clay at the Northeast of Penang Island

A series of subsurface investigation including in-situ and laboratory tests has been carefully planned and executed for a proposed residential and commercial development over soft marine clay at Tg Tokong, Penang Island. This paper presents the approach taken in determining and developing fundamental geotechnical engineering design parameters of the soft clay. The subsurface investigation was carried out in two phases to suit the overall development implementation plan namely subsurface investigation done near-shore with about 70 nos of boreholes, 50 nos of cone penetration tests (CPT) and 100 nos of Mackintosh probes and those that were carried out off-shore with 72 Nos of boreholes. The samples extracted from the field work were subjected to grain size analyses, Atterberg limits, oedometer test and consolidated undrained compression. Subsequently, correlations were established between physical soil properties with undrained shear strength from field vane and laboratory tests. The subsurface investigation has suggested that the soft marine clay at the northeast of Penang island comprises of a very soft upper marine clay layer overlying a stiffer lower marine clay. An intermediate stiff clay is sandwiched between these two marine clay layers. The soft clay was also subjected to x-ray diffraction to observe the minerology make up. The primary clay mineral was kaolinite/chlorite followed by smectite. The clay is anticipated to pose minimum effect onto the swelling and compression behaviour.