Lateral swelling pressure induced in expansive soils upon wetting can adversely impact the performance and integrity of earthen structures and foundations. The yearly cost associated with damage to structures from expansive clays in the United States is estimated to exceed the loss associated with natural disasters such as earthquakes, floods, and hurricanes. The main objective of this dissertation is to provide new insight into the evolution of lateral swelling pressure in variably saturated expensive soils under infiltration via physical testing. In the first part of this study, a new laboratory-scale testing apparatus was built to measure lateral and vertical swelling pressures under anisotropic conditions. The testing apparatus was used to investigate the effect of compaction level on lateral swelling pressure in an expansive clay collected from central Arkansas. Results show that the higher the compaction, the higher the lateral swelling pressure. In contrast, compaction was found to have an insignificant effect on the vertical swelling pressure at a compaction level of less than 90%. In the second part, the laboratory-scale testing apparatus was employed to test the effects of four additives (lime, lime kiln dust, cement, and cement kiln dust). The results showed that the addition of a high calcium additive could significantly reduce the swelling pressures of expansive clay. The third part of the dissertation involved full-scale testing of lateral pressures in an expansive clay upon infiltration. A heavily instrumented 3-m high masonry wall backfilled with an expansive clay was built and subjected to infiltration. The degree of saturation, pore-water pressure, temperature, suction, and lateral and vertical pressures were monitored at different locations during the test. Results showed that the development of lateral pressure is rapid during initial saturation and levels out as the clay approaches saturation levels. This finding highlights the importance of monitoring lateral pressure over time to accurately predict its behavior. The study also found that lateral pressure develops prior to vertical pressure, depending on the area and restraint.

The boundary value problems (BVPs) of geomechanics are challenging due to the complexity in modeling soil behavior and difficulties in modeling large deformations. While traditional numerical schemes have struggled in realistically simulating geomechanical BVPs, new numerical methods –such as the material point method (MPM)–are increasingly being used to tackle these problems. However, algorithms in MPM have not yet been sufficiently developed, scrutinized, and validated. This thesis focuses on the development, verification, and validation of MPM for use in geomechanical BVPs. In particular, the thesis focuses on simulation of cone penetration tests in both controlled environments and in field conditions.<div><br></div><div>To efficiently simulate cone penetration, a silent boundary scheme, known as a cone boundary, was proposed in the generalized interpolation material point method (GIMP), a variant of MPM. The implementation of the cone boundary in GIMP was discussed, and the boundaries were validated by comparison against several benchmark problems. The cone boundaries were shown to be suitable in transmitting energy at the boundary. In addition, the implementation of traction boundaries in GIMP was analyzed. In GIMP, traction boundaries may be implemented either at the centroid of the material point, or at the edge of the material point domain. It was shown that the implementation of traction boundaries at the edge of the domain led to stress oscillations near the boundary, which were minimized when the traction boundaries were implemented at the edge of the domain.<br></div><div><br></div><div>During cone penetration, the soil near the cone-soil interface is pushed to large strains. At large strains, soils reach critical state, a state in which the soil shears at constant volume. Simulation of incompressible materials using low-order shape functions commonly used in GIMP leads to stiffer solutions and stress oscillations. To mitigate the constraints imposed by incompressibility, the non-linear B-bar method was implemented in GIMP. The modifications required for the implementation of the B-bar method in GIMP were discussed, and the efficacy of the method in mitigating incompressibility was demonstrated by analyzing several benchmark problems.<br></div><div><br></div><div>To simulate cone penetration in saturated soil, a coupled formulation was proposed in GIMP.A single material point was used to represent both the soil matrix and water. The governing equations were solved using an explicit scheme with the velocity of the soil matrix and the velocity of water as the primary variables. The formulation was validated through problems for which analytical or numerical solutions are available.<br></div><div><br></div><div>Finally, cone penetration analyses were performed both in dry sand and saturated clays. Two bounding surface models –one for sand and one for clay –were used for accurately capturing the soil response. Cone penetration tests were performed on Ottawa 20-30 sand under a variety of loading conditions at a large calibration chamber. The penetration resistances were measured, and the displacement fields were captured using the digital image correlation technique(DIC). The cone penetration resistances predicted by MPM were within 25% of the measured values, and the displacement fields computed using MPM were similar to those captured using DIC. For saturated clays, cone penetration test results reported in the literature for a Boston Blue Clay (BBC) test site were used. The simulated cone resistance of 650 kPa lied within the CPT resistance range of 580-730 kPa reported in the field. The results demonstrate the capability of MPM in simulating cone penetration in both sands and clays provided that sufficiently accurate algorithms and advanced constitutive models capable of reproducing realistic soil behavior are used in the analyses.<br></div>

Geotechnical engineering works are part of almost all construction and infrastructure projects. The geotechnical engineering work contributes to the impact on the environment and gives rise to costs throughout its life cycle. Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) are established methods for evaluating a product's environmental impact and costs. However, the use of these methods is not extensive for geotechnical engineering works. A literature review showed that there is published research, but as the research topic is relatively new, there are many research gaps. A few topics in geotechnical engineering are better investigated than others and the entire life cycle is often not evaluated, usually only the production and construction stages. Although LCA and LCCA are established methods, the methodology for evaluating geotechnical engineering works needs further development to increase the evaluation work of sustainability aspects. In this licentiate thesis, a methodology is presented of how LCA and LCCA can be integrated into the geotechnical design process. The integration enables changes to the geotechnical design to further reduce the LCA and LCCA result, which is presented in the methodology. The methodology also presents a way to evaluate the possible geotechnical designs to select the most sustainable design based on the LCA and LCCA results. The thesis also presents the performance of LCA and LCCA for geotechnical engineering works and solutions to several difficulties that the geotechnical engineer may encounter during the evaluation of environmental impact and costs. / Geotekniska konstruktioner är en del av i stort sett alla konstruktions- och infrastrukturprojekt. Den geotekniska konstruktionen bidrar till påverkan på miljön samt ger upphov till kostnader under hela sin livscykel. Livscykelanalys (LCA) och livscykelkostnadsanalys (LCCA) är etablerade metoder för att utvärdera en produkts miljöpåverkan respektive kostnader. Användningen av dessa metoder är dock inte stor för geotekniska konstruktioner. En litteraturgenomgång visade att det finns publicerad forskning men då forskningsämnet är relativt nytt finns det många forskningsluckor. Ett fåtal ämnen inom geoteknik är bättre utredda än andra och hela livscykeln är oftast inte utvärderad utan vanligtvis endast produktions- och konstruktionssteget. Trots att LCA och LCCA är etablerade metoder behöver metodiken för utvärdering av geotekniska konstruktioner utvecklas för att öka utvärderingsarbetet av hållbarhetsaspekter. I denna licentiatuppsats presenteras en metodik för hur LCA och LCCA kan integreras i den geotekniska designprocessen. Integreringen möjliggör ändringar av den geotekniska designen för att ytterligare reducera LCA- och LCCA-resultatet vilket presenteras i metodiken. Metodiken redovisar även ett sätt för att utvärdera de möjliga geotekniska designerna för att utifrån LCA- och LCCA-resultaten välja den mest hållbara designen.  Uppsatsen redovisar även utförandet av LCA och LCCA för geotekniska konstruktioner och lösningar på ett flertal svårigheter som geoteknikern kan påträffa under utvärderingen av miljöpåverkan och kostnader. / <p>QC 230313</p>

Cone penetration in sands is a complex process: it contains several challenges that geomechanicians face, such as large displacements, large strains, strain localization, and microscale phenomena such as particle crushing and sand fabric evolution. In order to gain a deeper understanding of the penetration process and the mechanisms controlling penetration resistance, capturing these displacement and strain fields and microscale phenomena is necessary. Furthermore, as more sophisticated theoretical models become available for the simulation of the cone penetration problem, the experimental validation of those methods becomes vital.<br><div><br></div><div>This dissertation presents a multiscale study of the cone penetration process in silica sands. The penetration problem is investigated using a combinational approach consisting of calibration chamber experiments, digital image correlation (DIC) analysis, and X-ray computed Tomography (XCT) scans. Three silica sands with different particle characteristics are used in the experimental program. These three sands have similar particle size distributions; however, they differ in particle morphologies and particle strengths. These differences allow a study of the effect of microscale sand properties on the macroscale response of the sands to the cone penetration process. The three silica sands used in this research are fully characterized using laboratory experiments to obtain particle size distributions, particle morphologies, particle crushing strengths, minimum and maximum packing densities, and critical-state friction angles. Subsequently, both dense and medium-dense samples of the three sands are compressed in a uniaxial loading device placed inside an X-ray microscope (XRM) and scanned at multiple stress levels during uniaxial compression. Results from uniaxial compression experiments indicate that: (1) the compressibility of the sands is closely tied to particle morphology and strength, and (2) the anisotropy in the orientations of interparticle contact normals generally increases with axial stress; however, this increase is limited by the occurrence of particle crushing in the sample.<br></div><div><br></div><div>Subsequently, cone penetration experiments are performed under different confinement levels on dense samples of the three sands in aspecial half-cylindrical calibration chamber equipped with DIC capabilities. For each penetration experiment, incremental displacement fields around the cone penetrometer are obtained using DIC analysis, and these incremental displacement fields are further analyzed to compute the incremental strain fields. A novel methodology is developed to obtain the shear-band patterns that develop around the penetrometer automatically. Furthermore, differences in the shear-band patterns in deep and shallow penetration environments are also investigated. Results show that strain fields tend to localize intensely near the penetrometer tip, and the shear bands tend to develop along the inclined face and near the shoulder of the penetrometer. Significant differences in the shear band patterns in deep and shallow penetration environments are also observed.<br></div><div><br></div><div>After each cone penetration experiment, a specially developed agar-impregnation technique is used to collect minimally disturbedsand samples from around the penetrometertip. These agar-impregnated sand samples are scanned in the XRM to obtain 3D tomography data, which are further analyzed to quantify particle crushing around the penetrometer tip. The results show that: (1) for a given sample density, the amount of crushing around the cone penetrometer depends on the confinement and the sand particle characteristics, (2) the level of crushing is not uniform around the penetrometer tip, with more severe crushing observed near the shoulder of the penetrometer, and (3) the regions with more severe particle crushing around the penetrometer approximately overlap with regions of high shear strain and volumetric contraction. A framework is also proposed to obtain the ratio of penetration resistance in more crushable sands to penetration resistance in less crushable sands. Furthermore, a novel resin-impregnation technique is also developed to collect undisturbedsand samples from around the penetrometer tip. The resin-impregnated sand sample collected after one of the penetration experiments is scanned in the XRM to obtain the 3D tomography data, which is then analyzed to obtain the distribution of interparticle contact normal orientations at multiple locations around the penetrometer tip. These analyses indicate that the interparticle contact normals tend to orient themselves with the incremental principal strains around the penetrometer: below the penetrometer tip, the interparticle contact normals orient vertically upwards, while closer to the shoulder of the penetrometer, the interparticle contact normals become more radially inclined.<br></div><div><br></div><div>Data presented in this dissertation on penetration resistance, incremental displacement fields, incremental strain fields, particle crushing, and interparticle contact normal orientations around the cone penetrometer are aimed to be useful to researchers working on the multiscale modeling of penetration processes in granular materials and aid in the further development of our understanding of penetration processes in sands.<br></div>

<p>  </p> <p>Knowledge of the displacement and deformation fields beneath foundation elements obtained from carefully executed experiments is required to validate state-of-the-art numerical simulations, which in turn enable the development of better foundation design methods. This dissertation presents the results of an experimental program in which load tests were performed on model footings in a half-cylindrical calibration chamber with a transparent viewing window across its diameter. The digital image correlation (DIC) method was used to obtain the strain and displacement fields in the soil from digital images taken during the tests. Tests performed on both smooth and rough footings show a significant dependence of resistance on footing base roughness, with the DIC results providing insight into the reasons for that dependence. The experimental bearing capacity results are used to validate a previously proposed method in which an equivalent friction angle is used for calculation of the bearing capacity of footings in sand.</p> <p>Schmertmann's method is one of the traditional methods for estimating the settlement of axially loaded footings in sand using cone penetration test (CPT) data. The method was developed for footings placed on the surface of a single, uniform sand layer; it assumes a depth of influence below the footing base within which most of the soil deformations take place and an influence diagram to quantify the influence factor as a function of depth. However, the literature contains limited information on the strain influence diagrams for footings on layered sands, and, as a result, there is no way to accurately account for the effect of sand layering on footing settlement. In this study, Schmertmann's approach for calculating the strain influence factor is modified to account for the effect of two sand layers with varying thickness and relative density. Penetration experiments were performed using a half-square model footing (width <em>B</em> = 90 mm) placed on the surface of both single and two-layered (dense over medium-dense and medium-dense over dense), air-pluviated, silica sand samples prepared inside a half-cylindrical calibration chamber designed for digital image correlation (DIC) analysis. The test results indicate that both the thickness and relative density of the top sand layer (the layer in contact with the footing base) affect the parameters of the strain influence diagram. For dense sand over medium-dense sand, the depth to the peak strain influence factor varies with the thickness of the dense layer; however, when the thickness of the dense layer is 1.5<em>B</em> or greater, the strain influence diagram is similar to that obtained for a single, uniform sand layer. In contrast, for medium-dense sand over dense sand, the peak value of the strain influence factor varies with the thickness of the medium-dense layer up to a value of 1<em>B</em>. Based on the results obtained in this study, new strain influence diagrams are proposed for settlement calculation of square footings on two-layered sand profiles. The proposed method for estimation of footing settlement in layered sand is validated against measured data obtained from a full-scale, instrumented footing load test reported in the literature. </p> <p>The expressions for the shape and depth factors available in the literature for bearing capacity calculation are mostly empirical and are based on results obtained using limit analysis or the method of characteristics assuming a soil that is perfectly plastic following an associated flow rule. This study presents the results of an experimental program in which load tests were performed on model strip and square footings in silica sand prepared inside a half-cylindrical calibration chamber with a transparent visualization window. The results obtained from the model footing load tests show a significant dependence of footing penetration resistance on embedment depth. The load test results were subsequently used to determine experimentally the shape and depth factors for model strip and square footings in sand. To obtain the displacement and strain fields in the sand domain, the digital image correlation (DIC) technique was used to analyze the digital images collected at different stages during loading of the model footing. The DIC results provide insights into the magnitude and extent of the vertical and horizontal displacement and maximum shear strain contours below and around the footing base during penetration.</p> <p>The loading of a footing in sand generates substantial shear bands as a mechanism for failure develops with the formation of slip surfaces. The interaction of sand particles in the shear band governs its constitutive response to loading. This study provides the results of loading experiments performed under different conditions on half-square model footings (width <em>B</em> = 90 mm) in dense air-pluviated silica sand samples prepared in a half-cylindrical calibration chamber equipped with an observation window that allows collection of images of the sand domain during testing. Two sands (Ottawa sand and Ohio Gold Frac sand) with different roundness (angularity) were used to perform these experiments. The digital image correlation (DIC) technique was used to obtain the incremental strain fields in the sand domain. The zero-extension line (ZEL) concept was then used to study the shear strain localization process and to obtain the orientation of the shear bands from analysis of the incremental strain fields. The results show that sand particle morphology, footing surface roughness, load eccentricity, and depth of embedment of the model footing have an impact on the dominant shear band patterns that develop below the model footings, and, as a result, all of these factors affect the unit bearing capacity of footings. The estimated thickness <em>t</em>s of the shear band from the experiments is approximately 6<em>D</em>50 for Ottawa sand and approximately 8<em>D</em>50 for Ohio Gold Frac sand. </p>

Coal mine impoundment failures have been well documented to occur due to an increase in excess pore pressure from sustained monotonic loads. Very few failures have ever occurred from dynamic loading events, such as earthquakes, and research has been done regarding the stability of these impoundment structures under such natural seismic loading events. To date no failures or damage have been reported from dynamic loading events caused by near-by production blasting, however little research has been done considering these conditions. Taking into account that current environmental restrictions oblige to increase the capacity of coal impoundments, thus increasing the hazard of such structures, it is necessary to evaluate the effects of near-by blasting on the stability of the impoundment structures. To study the behavior of excess pore pressure under blasting conditions, scaled simulations of blasting events were set inside a controlled sand tank. Simulated blasts were duplicated in both saturated and unsaturated conditions. Explosive charges were detonated within the sand tank at various distances to simulate different scaled distances. Information was collected from geophones for dry and saturated scenarios and additionally from pressure sensors under saturated conditions to assess the behavior of the material under blasting conditions.

Pipelines used for the transportation of oil and gas products offshore are often buried beneath the seabed for protection from mechanical damage and for thermal insulation. During high temperature and high pressure operations, these pipelines are susceptible to resurfacing behaviour known as upheaval buckling, a structural response that is strongly influenced by the resistance of the surrounding soil. Despite much previous research on pipe uplift, the influence of the initial soil state – particularly in loose and liquefiable soil conditions – on the uplift resistance and corresponding buckling behaviour of the pipe is not well understood. This thesis presents research that examines the implications of these backfill conditions in the context of the global behaviour of the pipeline. The work consists of plane-strain monotonic uplift experiments focusing on density, rate, and stress level effects on the initial pipe-soil response. This is followed by numerical modelling of the global buckling behaviour using the experimental data as inputs. Finally, plane-strain cyclic experiments examine the possibility of progressive upward displacements over a number of cycles causing eventual upheaval buckling. A key finding from the uplift tests is that very loose backfill conditions may result in a localised flow-around failure mechanism, associated with lower peak resistance and a softer force-displacement response than with the sliding block mechanism that is typically assumed. This leads to lower peak buckling loads/temperatures than those predicted by current design guidelines. High quality data from both the monotonic and cyclic experiments was used to assess and suggest improvements to design guidance for these conditions.

This thesis presents experimental work and numerical analysis that has been undertaken to assess the bearing capacity of perforated offshore foundations. Perforated foundations may be used to support subsea infrastructure, including as mudmats into which a number of perforations have been made, or as grillages which consist of a series of structurally connected strip footings. Larger gravity base foundations, such as for offshore wind turbines or oil and gas platforms, may adopt a single central perforation. The advantages of using perforated foundations can include reduced material requirements and easier offshore handling as a result of smaller weight and lower hydrodynamic forces during deployment. Limited guidance currently exists for assessing the bearing capacity of these foundation types. Bearing capacity of perforated foundations has been examined in this thesis under conditions of combined vertical, horizontal and moment loading which is typical in offshore settings. Undrained soil conditions have been considered, except for the case of grillages in which drained conditions are often most relevant. Experimental work has included centrifuge testing of ring and square annular foundations on clay, and 1g testing of grillage foundations on sand. Finite element modelling has also been undertaken to assess perforated foundation capacity. A Tresca material subroutine (UMAT) and an adaptive meshing scheme have been developed to improve the accuracy of the finite element analysis carried out. The results showed that perforated foundations can be an efficient foundation solution for accommodating combined loading. As a ratio of their vertical load capacity, perforated foundations may be able to withstand higher moment and horizontal loads compared with unperforated foundations. The experimental and numerical results have been used to develop design expressions that could be employed by practitioners to estimate the vertical and combined load bearing capacity of these foundation types.

The Mechanistic Empirical Pavement Design Guide (MEPDG) developed by the National Cooperative Highway Research Program (NCHRP) project 1-37A, is a very powerful tool for the design and analysis of pavements. The designer utilizes an iterative process to select design parameters and predict performance, if the performance is not acceptable they must change design parameters until an acceptable design is achieved. The design process has more than 100 input parameters across many areas, including, climatic conditions, material properties for each layer of the pavement, and information about the truck traffic anticipated. Many of these parameters are known to have insignificant influence on the predicted performance During the development of this procedure, input parameter sensitivity analysis varied a single input parameter while holding other parameters constant, which does not allow for the interaction between specific variables across the entire parameter space. A portion of this research identified a methodology of global sensitivity analysis of the procedure using random sampling techniques across the entire input parameter space. This analysis was used to select the most influential input parameters which could be used in a streamlined design process. This streamlined method has been developed using Multiple Adaptive Regression Splines (MARS) to develop predictive models derived from a series of actual pavement design solutions from the design software provided by NCHRP. Two different model structures have been developed, one being a series of models which predict pavement distress (rutting, fatigue cracking, faulting and IRI), the second being a forward solution to predict a pavement thickness given a desired level of distress. These thickness prediction models could be developed for any subset of MEPDG solutions desired, such as typical designs within a given state or climatic zone. These solutions could then be modeled with the MARS process to produce am “Efficient Design Solution” of pavement thickness and performance predictions. The procedure developed has the potential to significantly improve the efficiency of pavement designers by allowing them to look at many different design scenarios prior to selecting a design for final analysis.

Earth pressure balance (EPB) tunnelling machines are commonly used for the construction of tunnels in soft soils. These machines use the excavated soil in a pressurised head chamber to apply a support pressure to the tunnel face during excavation. How well an unstable face is supported in an EPB machine depends on effectively transferring a constant pressure from the support medium to the surface of the face. If the support pressure is not constant, but instead changes, the varying pressure inevitably leads to collapse of the face or heave on the surface ground. A machine may be designed to work in “Ideal ground” conditions. However, natural soils rarely have these properties, and conditioning of the soil is usually necessary to change its properties to suit the machine. Effective soil conditioning significantly improves the machine performance and control of the soil flow through the screw conveyor. However, for soil conditioning as commonly used in practice, the effects of different conditioning treatments on soil properties and the machine performance are not clearly understood, and problems with EPB machine operations related to the soil properties are often encountered. This thesis presents experimental investigations of direct shear box tests on conditioned sands, compressibility tests on conditioned sands and a model EPB screw conveyor operating with sandy soils. Index tests were performed to investigate effects of foam and polymer conditioning treatments on the plastic fluidity of different Leighton Buzzard (L.B.) sands and Thanet sand. The index tests allowed assessment of conditioning treatments for sandy soils, and optimum ranges of treatments for Leighton Buzzard sand and Thanet sand are suggested. In the series of shear box tests, performed on conditioned Thanet sand and conditioned L.B. sands, one of the most important findings was that the pore water pressure controls the strength of the sand foam mixtures. An increase in foam injection ratio (FIR) might produce an increase of pore water pressure and a decrease of shear stress. In the series of compressibility tests, performed on conditioned Thanet sand and conditioned L.B. fine sand, one of the most important findings was that increasing FIR does not increase maximum gas expelled. The FIR and the initial relative density of the specimen have to be related to the capability of the specimen to retain the gas and establish a coexistence between grains of soil, water and gas bubbles. Finally, from the series of model (1:10 scale), screw conveyor tests, performed on conditioned Thanet sand, conditioned L.B. fine sand and conditioned Garside sand, it can be concluded that the Oxford screw conveyor model can be used as a trial machine to study the effects of different operating conditions on conditioned sand specimens similar to those used on site. This can allow choice of conditioning methods to improve the performance of an EPB machine at a given site.