Geotechnical Parameters Research Articles

Predicting Soil Swelling Potential Using Soil Classification Properties

Despite extensive research on unsaturated soil behavior in recent decades, the field of transportation engineering still lacks technically and economically feasible methods for identifying expansive soils along roads, particularly in regions with limited laboratory infrastructure that are distant from developed areas in Brazil. This situation is particularly evident in the state of Acre, located in the southwest of the Brazilian Amazon, where the subgrade predominantly consists of fine, plastic soils and faces challenges of limited availability of crushed stone and high precipitation levels. The volumetric variation of expansive soils in Acre has resulted in significant financial losses and has affected the lives of the local population. This paper proposes a simplified method for the preliminary identification of expansive clays, which is based on geotechnical characterization tests that can be performed at local laboratories. The proposed method utilizes the correlation between the plasticity index (PI) and silt/clay content to determine ranges that express the highest probability of occurrence of soils susceptible to shrink-swell behavior. This method was developed by correlating geotechnical parameters of 321 samples from EMBRAPA's SiSolos database with a geotechnical database of 100 local samples.

Utilizing expansive soil treated with phosphogypsum and lime in pavement construction

This study investigated the use of phosphogypsum (PG) in the long term as a construction material, especially in pavement structures. This study aimed to investigate the effect of increasing PG percentages on the geotechnical parameters of Expansive Soil. Extensive laboratory tests were conducted on both natural and PG-stabilized soil mixtures to examine their compaction properties, consistency limitations, swelling and linear shrinkage, pH values, and unconfined compressive strength (UCS), California bearing ratio (CBR), scanning electron microscopy (SEM), and X-ray Diffraction (XRD). The results showed that the PG addition would significantly reduce soil plasticity, linear shrinkage, and swell potential. Despite these improvements, the study concluded that treating the soil using PG only did not affect its physical properties sufficiently to be considered as a pavement subbase. As an alternative, lime was supplemented to the soil-PG mixture and noticed that a blend of 30% PG and 4% lime significantly improved soil strength, thereby rendering it appropriate for utilization as a pavement subbase layer. The Mechanistic-Empirical Pavement Design Guide (MEPDG) was utilized to assess the performance of pavement sections formed with PG-treated and untreated soils. As a result, this study contributes to the development of an environmentally sustainable PG waste management system while also demonstrating its potential uses in roadway construction.

Uncertainty quantification for granular materials with a stochastic discrete element method

Significant uncertainty exists in granular materials, as demonstrated by experimental and simulation studies. Quantifying this uncertainty by integrating refined discrete element analysis with direct stochastic simulation is challenging due to computational cost constraints. To this end, the probability density evolution method (PDEM) is introduced to propose the methodology of stochastic discrete element analysis. The objective of this paper is to develop a formulation of the stochastic discrete element method (DEM) on uncertainty quantification for granular materials. First, the uncertainty characterization of inter-particle friction coefficients (μ) is performed via experimental data, resulting in the identification of an optimal probability distribution. Second, the 100 representative deterministic points of basic random variables are selected for subsequent DEM shearing simulation until the critical state. Third, the PDEM is developed to obtain the probability density function (PDF) surface representing the system’s performance, thus offering a comprehensive prediction of uncertainty for granular materials. The results show that the uncertainty of μ propagates to the behavior of granular materials. Utilizing the stochastic DEM methodology clarifies which behavior parameters exhibit significant randomness and which possess negligible randomness. Notable uncertainties are observed in large strain macro-scale behavior and the proportion of inactive particles. It can be inferred that conventional methods that neglect probability distributions might produce spurious results. Moreover, the influence of uncertainties on granular material behavior varies depending on the its shearing state and related soil parameters. In contrast, limited uncertainties are identified for the randomness of small strain stiffness, and the randomness on the particle scale stress transmission shape is also limited. This study marks the initial application of the PDEM in geotechnical engineering, suggesting that considering probability density evolution could enhance geotechnical engineering design. The current study highlights the necessity of using statistical methods to assess key geotechnical parameters.

Seismic monitoring of strength in stabilized foundations by P-wave reflection and downhole geophysical logging for drill borehole core

Abstract Evaluating the subground properties during the initial stage of a construction of building is important in order to estimate the suitability of soil quality to the technical requirements of bearing capacity, resistance to stress, and strength. This study presented the evaluation of the geotechnical properties of soil intended for the construction of Max IV facility of Lund University, performed in fieldwork and laboratory. The in situ methods included drilling boreholes, core sampling and assessment, crosshole measurements, and borehole logging. The laboratory-based measurements were performed at Swedish Geotechnical Institute and combined seismic measurements of drill cores, determination of the uniaxial compressive strength (UCS), and examination of material property: sieve analysis and natural moisture content. UCS was evaluated with regard to velocities of elastic P-waves. The synchronous light test by X-ray diffraction was performed for qualitative analysis of mineral composition of samples. The study applied integrated approach of the diverse geophysical methods to solve practical tasks on the evaluation of foundation strength and geotechnical parameters. This study demonstrated the benefits of integrated seismic and geophysical methods applied to soil exploration in civil engineering for testing quality of foundation materials.

Non-Probabilistic Reliability Analysis of Slopes Based on Fuzzy Set Theory

Aimed at the problem of fuzzy uncertainty of geotechnical parameters in slope stability analysis, a non-probabilistic reliability analysis method for slopes based on fuzzy set theory is proposed. Geotechnical parameters are described as fuzzy numbers, which are transformed into interval numbers at different cut set levels by taking fuzzy sets. The corresponding non-probabilistic reliability indexes and failure degrees of the slope are calculated by the non-probabilistic reliability analysis method based on the ellipsoidal model, and then the overall failure degree of the slope is obtained by weighted average to judge the stability state of the slope. The feasibility of the method was verified by a case analysis. The results show that the type and shape parameters of the fuzzy affiliation function of geotechnical parameters have a great influence on the non-probabilistic reliability of the slope. The slope failure degrees obtained from trapezoidal fuzzy numbers were larger, the slope failure degrees obtained from triangular fuzzy numbers and normal fuzzy numbers were medium, and the slope failure degrees obtained from lognormal fuzzy numbers were smaller. When considering soil parameters as triangular fuzzy numbers, normal fuzzy numbers, or lognormal fuzzy numbers, with the reduction of the shape parameters, the non-probabilistic reliability indexes of the slope increased while the failure degrees decreased. Additionally, adopting the overall failure degree to evaluate the stability of the slope can effectively solve the problem where the calculation results are too conservative (if the non-probabilistic reliability index is greater than 1) to judge the stability state of the slope in the traditional non-probabilistic reliability method.

Determination of rock mass integrity coefficient using a non-invasive geophysical approach

Determination of rock mechanical parameters is the most important step in rock mass quality evaluation and has significant impacts on geotechnical engineering practice. Rock mass integrity coefficient (KV) is one of the most efficient parameters, which is conventionally determined from boreholes. Such approaches, however, are time-consuming and expensive, offer low data coverage of point measurements, require heavy equipment, and are hardly conducted in steep topographic sites. Hence, borehole approaches cannot assess the subsurface thoroughly for rock mass quality evaluation. Alternatively, use of geophysical methods is non-invasive, rapid and economical. The proposed geophysical approach makes useful empirical correlation between geophysical and geotechnical parameters. We evaluated the rock mass quality via integration between KV measured from the limited boreholes and inverted resistivity obtained from electrical resistivity tomography (ERT). The borehole-ERT correlation provided KV along various geophysical profiles for more detailed 2D/3D (two-/three-dimensional) mapping of rock mass quality. The subsurface was thoroughly evaluated for rock masses with different engineering qualities, including highly weathered rock, semi-weathered rock, and fresh rock. Furthermore, ERT was integrated with induced polarization (IP) to resolve the uncertainty caused by water/clay content. Our results show that the proposed method, compared with the conventional approaches, can reduce the ambiguities caused by inadequate data, and give more accurate insights into the subsurface for rock mass quality evaluation.

Development and evaluation of coal mine waste materials for gainful utilization

Coal mine overburden and thick inseam parting materials found in the lower Gondwana basin are treated as mine wastes. Unused fly ash from coal-fired plants is another waste material. This investigation focused on using these wastes to develop better composite materials. Composite materials of varying compositions with coal mine wastes from 50 to 90% and fly ash from 10 to 50% with 2–6% cement additives were developed and evaluated. Their physical, chemical and geotechnical properties were determined. Ordinary Portland cement strongly influenced the geotechnical parameters. The fly ash content was optimized for unconfined compressive strength (UCS) and California bearing ratio for both mine wastes. Composite materials with 70% overburden, 30% fly ash and 6% cement showed a UCS of 4.01 MPa at 56 days. Composites with 80% inseam parting, 20% fly ash and 6% cement produced 4.90 MPa UCS at 56 days. Linear correlations were observed between fly ash percentage in the two composites and their UCS values. Pearson’s and Spearman’s coefficients produced a high correlation of −0.9 for the composite prepared with parting material. Microstructural analysis showed calcium silicate hydrate gel formation occurring at 28 days. The composites meet the strength criterion for the base and subbase of coal mine haul roads.

Analysis and Estimation of Seepage through Homogeneous Earth Dams Using Neural Network and Empirical Equation

In this investigation, the quantity of seepage through a homogeneous earth dam with a vertical drain on a permeable foundation was studied using the SEEP/W program. Moreover, the effects of the geometrical and geotechnical parameters (upstream slope, dam height, top width, free board, and permeability ratio) on leakage flow were analyzed with SPSS 20. To begin with, leakage flow values through an earth dam were estimated using SEEP/W by taking three values of each parameter, and then statistical analysis was performed with the help of dimensional analysis. In addition, an empirical equation and a neural network model dubbed q_ANN were developed to calculate leakage flow through an earth dam with a vertical drain. The validation of these models (empirical equation and q_ANN) is made by their applications to real case studies such as El-Haimeur and Boubrik dams located in Ghardaia City. In conclusion, the values of these models can prove that the performance of the models is high and accurate to predict leakage flow through a homogeneous earth dam with a vertical drain on a permeable base.

Experimental investigation of the effect of landfill leachate on the mechanical and cracking behavior of polypropylene fiber-reinforced compacted clay liner.

This paper aims to investigate the effect of leachate on the geotechnical parameters and the cracking behavior of compacted clay liners (CCLs) containing different percentages of polypropylene fibers. Accordingly, 200 compacted clay samples were reinforced with different percentages of fiber contents (FC) (i.e., 0, 0.5, 0.75, and 1%) and prepared with water or leachate to conduct different laboratory tests. First, the physical properties of the clay were determined. Then, the shear strength parameters (i.e., cohesion and friction angle), unconfined compressive strength, and the hydraulic permeability were determined subjected to water or leachate. Notably, the cracking behavior was modeled using visual images of the samples. The leachate increased desiccation cracks in the natural soil from 0.425 to nearly 1.111%. However, the addition of 0.5% (in the case of water) and 1% (in the case of leachate) fiber to the soil reduced the surface desiccation cracks in clay liners to about 0.185 and 0.352%, respectively. In both water- or leachate-prepared samples, the addition of fibers significantly increased the cohesion and friction angle. The shear strengths of the unreinforced leachate-prepared samples were lower than those of the water-prepared samples. The shear strength and unconfined compressive strength of all specimens increased with increasing fiber percentage. The presence of fibers in all samples caused more ductile behavior. The required amount of energy to achieve the maximum strength in the samples increased with increasing FC. By increasing the percentage of fibers, the permeability of the natural soil and the leachate-prepared samples increased. However, the highest permeability was observed in the leachate-prepared samples containing 1% fibers of 8.3 × 10-10m/s, which is less than 10-9m/s (maximum allowable permeability for clay liners). Finally, the obtained results were satisfactorily confirmed by scanning electron microscopy (SEM) analysis.

Comparing the Results of Geotechnical Tests with the Well Seismic Survey to Find the Dynamic Modulus of Elasticity for the Surface Soil Sections in Hilla City

The study area for Babylon Governorate is located roughly 110 kilometers from Baghdad, Iraq's capital city. Approximately 5,119 km2 of Iraq's total land area is occupied by it. The most common wind direction in Iraq is northwest. The results of the cross-hole survey using P and S-wave timings and velocities were discovered through a geophysical analysis of the area. In depths of 1 to 10 meters, the P-wave velocity was 482.01 m/sec and the S-wave velocity was 180.11 m/sec. 1.6-1.8 kn/m3 was the average bulk density of the research area's soils, with the lowest value of 1.6 kn/m3 in the depths of 1m and the highest value of 1.8 kn/m3 at 10 m. At depths of 1 to 10 meters, internal friction angles (ɸ) ranged from 15 to 30 degrees. The velocity values of P and S-wave increase with depth from the surface to the depth of 10 m because of the density increase with depth in the soil (the layer compaction or soil load). Based on the ratio of compressional and shear velocities of density, elasticity and geotechnical parameters were determined. There was a wide variation in Poisson's ratio (v) between 1-10 meters, which indicates that the soil in the research area is sandy clay. The soil is considered saturated when Ko is close to 1 and the concentration index Ic exceeds 3.

Evaluation of Light Falling Weight Deflectometer for In Situ Measurement of Secondary Deformation Modulus of Various Forest Road Pavements

Roads in forests are necessary for proper forest management and active protection of the natural environment. They facilitate tourism and recreation and have a very important function in firefighting. The cost of building roads in forest areas is considerable, even when relatively cheap materials such as aggregates of natural or anthropogenic origin are used. Therefore, any road investment must be well prepared and executed. Bearing capacity and compaction are among the most important and frequently used geotechnical parameters in road construction. The aim of this study was to determine the possibility of predicting the value of the secondary deformation modulus E2 (obtained from measurements with a static plate load test – PLT) based on measurements with a light falling weight deflectometer (LFWD) Zorn, type ZFG 3000 GPS with a drop weight of 10 kg. The regression analysis included 245 results of bearing capacity measurements carried out on 46 forest road sections with various road pavements. Different regression models were tested: linear, logarithmic, polynomial, exponential and power models, excluding polynomials of fourth and higher degree. Prediction of E2 (PLT) values from dynamic deformation modulus Evd (LFWD) values is possible. However, the reported unsatisfactory strength of the relationship between the two parameters is associated with a high risk of error (r=0.73, R2=0.54, Se=80.37 MN·m-2). Neither the use of more complex non-linear regression models nor the use of multiple regression by introducing an additional estimator in the form of the s/v ratio significantly improved the estimation results. The quality of the prediction of E2 values is not constant. It varies depending on the type of forest road pavements, the use of geosynthetic pavement reinforcements and the type of road subgrade. The study also found that the quality of E2 prediction can be improved by limiting the range of tested Evd values upwards. It is advisable to continue this type of research, as the results obtained could be the basis for developing national standards for the application of LFWD to control the bearing capacity and compaction of forest road surfaces in the future.

Geological-geotechnical investigations of the historical Diriyah urban zone in Riyadh, Saudi Arabia: an integrated approach

One hundred seventy geotechnical boreholes, two geo-seismic profiles of multichannel analyses of surface waves (MASW), and two geoelectrical cross-sections of electrical resistivity tomography (ERT) were carried out in the historical Diriyah urban zone. The borehole samples were analyzed for the geotechnical parameters of the standard penetration test (SPT N-value), the rock quality designation (RQD), and compressive strength (CS). Moreover, P- and S-wave velocities have been calculated. The measured SPT N-value has been corrected to amend the N60 parameter. According to the corrected N60, type, lithological, and soil profiles were divided into five distinct subsurface layers. It is indicated, for all recorded depths, these sediments become denser with depth where the values of N60 increase from 5 to 88 downward. According to grain size distribution, the major part of soil sites is composed of sand and varies from low to medium compressibility. The estimated RQD values range from 5 to 100 indicating rocks with significant variations in their geotechnical and physio-chemical characteristics. Furthermore, the compressive strength varies widely between 152.3 and 1,104.2 kg/cm2, which represents diverse geodynamic behavior under civil engineering constructions. Besides, the range of soil stiffness is indicated by the Shear-wave velocity (Vs) for soil layers, which varies from 171.3 to 456.2 m/s. According to the findings of the MASW profiles, the shear wave velocity is shown to be decreasing in MASW profile 1 between depths of 8 and 14 m, where the values range from 1,000 to 1,500 m/s, indicating a weak zone filled with secondary materials. But line 2 shows how the shear wave velocity decreased from depths of 5 m–11 m, where values ranged from 1,000 to 1,500 m/s, thus indicating a weak zone. The low resistivity zones in ERT cross-sections, which are found at the same depths in MASW profiles, are well associated with these findings. It can be concluded that there are a number of weak zones with varying depths, shapes, and dimensions found in the historical Diriyah urban zone’s near-surface deposits that civil engineers, urban planners, and urban developers should consider before undertaking any construction or developmental work involving civil engineering.

Enhanced elastic beam model with BADS integrated for settlement assessment of immersed tunnels

Excessive settlement may induce structural damage and water leakage in immersed tunnels, seriously threatening the tunnels’ safety. However, making accurate assessment of the settlement in immersed tunnels is difficult due to the incomplete knowledge of the geotechnical parameters and the inadequacy of the model itself. This paper proposes an effective method to accurately assess the settlement in immersed tunnels. An enhanced beam on elastic foundation model (E-BEFM) is developed for the settlement assessment, with the Bayesian adaptive direct search algorithm adopted to estimate unknown model parameters based on previous observations. The proposed method is applied to a field case of the Hong Kong–Zhuhai–Macao immersed tunnel. The original BEFM is used for comparison to highlight the better assessment performance of E-BEFM, particularly for joints’ differential settlement. Results show that the proposed method can provide accurate predictions of the total settlement, angular distortion (a representation of tubes’ relatively differential settlement), and joints’ differential settlement, which consequently supports the associated maintenance decision-making and potential risk prevention for immersed tunnels in service.

Geotechnical Characterization of Quito’s North-Central Zone as Applied to Deep Excavation in the Urban Setting

This paper describes an in-depth soil characterization study in the La Carolina financial district of Quito (Ecuador). As there was very little information available on the geotechnical structure of Quito’s volcanic soil, particularly in this area, where large-scale property development has taken place, the aim was to provide information on soil parameters to engineers working on large geotechnical and civil engineering projects based on the results of a thorough and comprehensive study of such properties. A series of field tests were performed at three different sites, where thin-walled tube samples were collected for lab testing to estimate the index properties and mechanical parameters. These index properties were then combined with conventional two-way drainage oedometer tests and stress-path triaxial testing to evaluate compressibility, stiffness and strength. The subsoil was found to be partly composed of slightly overconsolidated volcanic soils. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) analyses were also conducted to determine mineralogical and microstructural features and evaluate their influence on the mechanical behavior of the volcanic soil. This type of research is frequently applied to the study of landslides in urban environments, where it is essential to understand their failure mechanisms, especially in slopes generated by the construction of important engineering works. Therefore, based on this geotechnical characterization study, parameters were subsequently determined for the Mohr–Coulomb (MC), Hardening Soil (HS), and Hardening Soil with Small-Strain Stiffness (HSsmall) soil constitutive models, and these were applied to a numerical study of the Soil Nailing system behavior for the construction of a five-level underground car parking structure of an important building located in the north-central sector of the city of Quito. It was verified that the HSsmall and HS constitutive soil models better reproduce the behavior of this type of structure. Finally, the multiple geotechnical parameters determined in this study significantly contribute to the analysis of these structures in this soil type.

Analysis of instantaneous surface settlement of tunnel construction in composite stratum based on semi-analytical method

It is important for shield tunneling safety to predict and control the instantaneous surface settlement. Particularly, the complex geological condition can make accurate prediction more difficult. To adapt to the stratum distribution, a semi-analytical method is established by introducing the finite layer method into tunnel mechanical analysis. Firstly, based on the elastic solution of the finite layer method, the horizontal flexibility coefficient of tunneling and the surface settlement are obtained by applying effective thrust to the excavation face. Secondly, two influencing factors are analyzed, including the penetration of shield tunneling and the Poisson ratio of geotechnical parameter. The relationship formula between the measured value and the theoretical value of the maximum settlement is derived through data fitting. Finally, the settlement prediction method of tunneling is proved to be practical, which provide a new ideal for the mechanical analysis of tunnels in composite strata.

Mechanical behaviour of grouted sands with acrylates and polyurethane resins

Chemical grouting is a technique where solution-based binders are used to improve both mechanical and hydraulic properties of the soil or rocks. The following research study shows an extensive laboratory programme where a polyurethane (PU) and an acrylate (AC) were grouted in a tertiary sand under different water contents and relative density, with different gelling time and grouting conditions. Unconfined compressive strength, splitting tests, triaxial tests and creep tests on the grouted materials were conducted. A statistical interpretation considering the kernel probability density function was performed in order to understand the interdependency of the changing parameters. In general, PU-consolidated samples provide higher mechanical properties with respect to ACs; however, the effects and the dependency on the geotechnical base parameters are different.

The Effect of Soil Mineralogy and Particle Breakage on the Impulse Generated from Shallow Buried Charges

Historically, most testing with shallow buried charges has focussed on soils which are predominantly quartz (silica)-based. Particle size, moisture content and density have previously been investigated to ascertain their importance, along with other geotechnical parameters, in governing the magnitude of an impulsive output. This has shown that, in order of importance, moisture content, density and particle size drive the total impulse imparted. The work in this paper presents the results of blast testing carried out with carbonate sands to investigate the difference that particle mineralogy (and hence, propensity for breakage) has on both the localised loading and the total impulse using an array of 17 Hopkinson pressure bars known as the Characterisation of Blast Loading (CoBL) apparatus. Carbonate sands are thought to have more friable particles due to their plate-like morphology, as opposed to the rounded morphology of quartz-based sands. Testing was conducted with low moisture content samples and compared with the well-established Leighton Buzzard uniform sand to isolate the effect of particle mineralogy/morphology on the loadings measured. The results show that, despite attaining a 23% lower bulk density, carbonate soils deliver almost identical total impulses (0.7–3.0% higher) when compared with quartz soils for nominally identical moisture contents.

The effect of EPB face pressure on TBM performance parameters in different geological formations of Istanbul

This study summarizes the effect of EPB pressure varying from 0.5 bar to 4 bar, on TBM performance i.e., on thrust force, torque, penetration, and specific energy. 6511 data points were analyzed, each representing mean values attributed to different segments of 1.5 m in length, in four different fractured hard rock formations, in a transition/weathered complex zone, and in silty-clayey sand. From this study, it emerges that thrust and torque values almost increase up to 2.2 and 1.7 times with EPB face pressure changing from 0.5 to 4 bar in all formations studied except for torque in silty-clayey sand. However, after 2 bar of face pressure, the effect of EPB pressure on penetration and specific energy is more remarkable than the other parameters. Specific energy increases almost 2–2.5 times in silty-clayey sand and up to 4 times in a transition/weathered zone. To contribute to understanding better the factors affecting TBM performance in fractured hard rock, the effects of geological and geotechnical parameters are also discussed briefly. We think the results will serve as a basis to understand better the effect of EPB face pressures on TBM performance, to design more efficient EPB-TBMs, and to help to develop new performance prediction models for EPB-TBMs working in fractured hard rock formations and in soft ground if some correction coefficients as will be developed later, are added to previously published models. However, it is strongly recommended to use the results of this article for tunnels having similar geological conditions as in Istanbul.

Pile tip bearing capacity in rock masses: analytical and numerical analysis comparison

This paper researches the different approaches to calculate the ultimate bearing capacity at the pile tip embedded in a homogenous rock mass characterized by the modified Hoek and Brown failure criterion. The main objective is to analyze the performance of the novel Discontinuity Layout Optimization method (DLO), which directly calculates the limit load, instead of using a load convergence scheme, being first applied here to the complex problem of piles in rock. The DLO results are validated against the available analytical solution and the Finite Difference Method (FDM) results, for wide range of geometric and geotechnical parameters. Perfect plasticity, plane strain conditions, associated flow rule, the modified Hoek and Brown failure criterion, and weightless rock media are considered in all models. The comparison between solutions is expressed by a percentage difference considering the analytical solution or the numerical solution as a reference. Results relative to DLO and FDM differences against the analytical solutions point towards some limitations of the analytical solution and that the numerical model does not reproduce exactly the analytical solution hypotheses. From the analysis, DLO demonstrates to be a very efficient and accurate tool to address the tip-of-pile bearing capacity, presenting considerable advantages over other methods.

Engineering Geological Highway Structural Failure Assessment and Modeling of its Geotechnical Parameters: Case Study of Failed F- 209 Pavement, Southwestern Nigeria

Engineering Geological Highway Structural Failure Assessment and Modeling of its Geotechnical Parameters: Case Study of Failed F- 209 Pavement, Southwestern Nigeria