Thermal power station in most countries is saddled with the problem of fly ash disposal and unless suitable avenues are found for its proper use, this would pose a gigantic problem to the power sector. Disposal of huge quantities of fly ashes without proper care causes considerable impact on the environment particularly the one leading to soil and groundwater contamination. On the other hand, fly ashes have many desirable properties which can find applications in civil engineering, especially in geotechnical engineering. The pozzolanic reactivity is one of the important properties of fly ashes that enhance its application. Thought the fly ashes with self – pozzolanic property are well utilized, fly ashes with insufficient free lime, such as class F fly ashes are being grossly underutilized and they form a considerable portion of fly ashes that are disposed. Yet another factor restricting the use of fly ash is the concern about the leachability of lime under field conditions particularly under saturated or partially saturated conditions. Hence an attempt is made in this thesis, to reduce the lime leachability of class F fly ashes with different additives. Thus, selection of right amounts of additives to reduce the lime leacability is an important aspect studied in this thesis. Effect of such as strength, compressibility, and CBR value is also investigated. Another simple way to reduce the problem of disposal of fly ash is to utilize it for the construction of waste disposal sites particularly for lining solid waste disposal facilities in place of the natural clay materials which are very often procured by excavating and transporting from far off places. Also, the capacities of fly ashes to sorb heavy metal that are likely to be present in the leachates generated from the industrial wastes have been studied. Of the other factors limiting the generous use of fly ashes is the leachability of several trace elements present in them. Hence the leachability of trace metals from fly ashes under different practical situations, before and after incorporating the selected additives for improving the engineering properties of fly ashes, has been studied. The thesis is presented in 10 chapters. The relevant background for the studies and scope of the work is given Chapter 1. Sources of the fly ashes collected for the investigating along with their physical and chemical properties are presented in chapter 2. Two low line fly ashes are collected directly from the electronic precipitators of the thermal power plants located at Neyvelli town of the Tamil nadu and Maddanur town of Andhra Pradesh, India, named NFA and MFA respectively. MFA has greater finer particle content than NFA. The particles of MFA Have rougher surface compared to those of NFA. Both of fly ashes have predominantly quartz and mullite phase in them. The silica, total lime and carbon contents which have major influence on the pozzolanic reactivity of fly ashes vary considerably in the both the fly ashes. Lime leachability is taken as the amount of lime that is converted into soluble form (by dissociation into calcium and hydroxyl ions) under a standardized condition. It can be used to asses the long term sustainability of the strength achieved in fly ashes with lime. Lime leachability studies have been conducted on the fly ashes stabilized with different additives in specially designed moulds. Results presented in Chapter 3 showed that leachability of lime in fly ashes increases with the increase in lime content though it is not in proportion to the increase in lime content. This is because the solubility of lime is less and is independent of the total lime present. The marginal reduction in leachability is mainly due to cemented matrix of fly ash inhibiting the leaching of time. The higher the strength of the matrix the lower is the leachability. Further it is made clear that at any lime content presence of gypsum reduces the time leachability which has been attributed to the transformation of pozzolanic compounds into less soluble form than the compounds formed with lime alone. With the increase in curing period, the amount of lime that leaches from the lime-stabilized fly ashes as well as those treated with gypsum to a considerable extent. The nature of alteration does not seem to change with time as revealed by a good correlation between lime leachability ratios obtained after 7 days and 14 days of curing periods. Chapter 4 presents the results of unconfined compressive strength tests carried out on fly ashes with varying lime and gypsum contents, before soaking and also soaking in several heavy metal solutions, along with the durability to the cycle of wetting and drying. The results revealed that the strength of low lime fly ashes increases with lime content significantly up to the optimum lime content of about 2.5 – 5% and gradually thereafter. Addition of gypsum of 1 – 2.5% increases the strength of fly ashes further at any lime content. Increase in strength with gypsum, which is quite significant at lower lime contents initially, is observed for a considerable period (up to 180 days) at higher lime contents. The increase in strength is as high as 40-fold in some instances. This increase in strength which is also more durable has been attributed to the formation of calcium – sodium – aluminium - silicate hydrate along with calcium silicate hydrate. Further, it is observed that fly ash which responds better to lime stabilization shows accelerated gain in strength due to the addition of gypsum at early curing periods than the fly ash that responds solely to lime. Decrease in lime leachability ratio is a good indication of the increased strength along with the increased durability. California Bearing Radio (CBR) values are of great significance in the utilization of fly ashes in bulk quantities for the construction of road and railway embankments and pavements. Studies conducted to determine the CBR values of fly ashes with different lime and gypsum contents after curing for different time periods are described in chapter 5. The CBR values are observed to increase with lime alone significantly up to 2.5% and only marginally beyond. But the increase in CRB values is considerable with gypsum at any lime content. The increase in CBR value is particularly more with 2.5% gypsum for fly ashes with 2.5% lime. The CBR values of stabilized fly ashes are generally higher for 5 mm depth of penetration than those for 2.5 mm one due to the high stiffness of the matrix formed even at low strain levels. The loss in CBR values with soaking is relatively more at lower curing the periods due to the improper cementation of particles. Even after this significant loss in CBR values, fly ashes with 2.5% lime and 2.5% gypsum register the maximum values after curing under soaked condition. Unlike in the case of unconfined compressive strength, lime leachability values could not be well correlated with the CBR values of fly ashes with different lime and gypsum contents since many more factors influence the CBR values than those of unconfined compressive strength alone. Chapter 6.brings out the effects of addition of lime alone and lime along with gypsum on the compressibility behaviour of the fly ashes. Since the fly ashes when treated with additives develop strength and exhibit lower compression with the passage of time, consolidation testing with conventional duration of load increment may not be appropriate. Hence an attempt has been made to assess the minimum duration of load increment necessary to study the compressibility characteristics of such materials. Thus the compressibility behaviour of fly ashes with additives has been studied using conventional consolidation test with different durations of load increments varying from 30 minutes to 48 hours. The results indicated that 30 minutes of duration of load increment can be used to assess the compressibility behaviour of such materials. The effect of lime which reduces the compression is seen to be maximum from the results obtained with the load duration increment of 30 minutes but gradually reduce with higher duration of load increment. It has also been observed that the rate of decrease in the compressibility is maximum up to 2.5% lime and thereafter gradual. The compressibility of lime –treated fly ashes further reduces when gypsum is incorporated, the optimum gypsum percentage being 2.5. This reduction in the compressibility of fly ashes enhanced by incorporating lime and gypsum makes them versatile in the construction of embankments and for structural fills, particularly reducing the time required in between laying of each lift. It has been brought out that decrease in the lime leachability decreases the compressibility of fly ashes. Fly ash has potential application in the construction of base liners of waste containment facilities. While most of the fly ashes improve in the strength with curing, the ranges of hydraulic conductivities they attain may often not meet the basic requirement of a liner material. Attempts to reduce the hydraulic conductivity by adding lime as gypsum along with lime to both the fly ashes are presented in chapter 7. Hydraulic conductivities of the compacted specimens have been determined in the laboratory using the falling head methods. It has been observed that the addition of gypsum reduces the hydraulic conductivity of the lime treated fly ashes. The reduction in the hydraulic conductivity of the fly ashes containing gypsum is significantly more of sample with high amounts of lime contents (as high as 1000 times) than those with lower amounts of lime. However, there is relatively more increases in the strengths of the samples with the inclusion of gypsum to the fly ashes even at lower lime contents. This is due to the fact that excess lime added to fly ash is not effectively converted in to pozzolanic compounds. Even the presence of gypsum is observed not to activate these reactions with excess lime. On the other hand the higher amount of lime in the presence of gypsum is observed to produce more cementitious compounds which block the pores in the fly ash. Amount of lime leached in the found to be directly related to the hydraulic conductivity inspite of many –fold variations in the hydraulic conductivity achieved by curing fly ash with lime and gypsum. The consequent reduction on the hydraulic conductivity of fly ash would be beneficial in reducing the leachability of trace elements in the fly ash when used as base liner. Fly ash contains trace metals and other substances in the sufficient quantities which may leach out over a period of time. The study has been extended to examine the leachability of a few selected trace metals viz., Cd, Cu, Cr, Mn, Pb and Zn from fly ash before and after incorporating additives has been reported in chapter 9. The standard laboratory leaching test for the combustion residues developed by Van der Sloot et al. has been employed to study the leachabilities of trace elements as a function of liquid to solid (L/S) ratio and pH. The leachability test were conducted on the powdered fly ash samples obtained from unconfined compressive strength tests, conducted after a curing period of 28 and 180 days. It observed that, there is a marked reduction in the relative leachabilities of trace elements present, at the end of 28 days which reduced only marginally at the end of 180 days. Chapter 9 reports the retention capacities of fly ashes for copper, lead and zinc metals ions. Various parameters like contact time, initial concentration and pH have been varied and their effect on retention mechanism studied. The retention order of metals ions, Cu+ 2 > Pb+2>Zn+2, is observed to be the same for both the fly ashes at all pH values. The dominant mechanisms responsible for the retention are precipitation at higher pH’s as hydroxides and adsorption at lower pH’s Due to presence of silica and alumina oxide surface in fly ash. First order kinetic plots have revealed that the rate constant value increases with increase in initial concentration and pH. Langmuir adsorption isotherms have been plotted to study the maximum adsorption isotherms have been plotted to study the maximum adsorption capacities for metal ions under different conditions. The older indicates that the adsorption is predominantly by silica surface than that by alumina or iron oxide surfaces. This thesis demonstrates that incorporation of gypsum along with lime in the optimal proportions not only reduces the lime leachability but also greatly enhances the strength and CBR values, reduces the compressibility and minimizes the leaching of trace elements present in them enhancing the potential of fly ashes for many applications. Detailed conclusions are presented in chapter 10. The study greatly helps in promoting the use of fly ashes for many geotechnical and geo-environmental applications.

According to a 2012 American Coal Ash Association Coal production Survey Report, US coal fired power plants produced more than 109 million tons of waste that year. Approximately half of this waste is the valuable by-product fly ash. There are three classes of fly ash: cementitious class C and non-cementitious classes F and N. Over half of the fly ash produced is used in the geotechnical/construction industries. Most geotechnical soil stabilization studies using fly ash are focused on controlling shrink-swell potential of clays. This study utilized the less desirable class F fly ash to assess the improvement of shear strength parameters of granular soils. Two mix designs were developed and tested using consolidated undrained, unconfined compression, and triaxial testing. Mix designs consisted of 15% fly ash with 0.5 or 1% cement, and poorly graded Ottawa sand compacted using a standard effort at 10 percent moisture content. Consolidated undrained testing on Mix 1, which included flushing and saturating the specimens, produced higher shear strength parameters than for the sand alone. However, the results were inconsistent with respect to the increase in shear strength parameters with time. Unconfined compression testing was then conducted on both Mix 1 and Mix 2 to assess strength gain with time. Results showed both mixes gained appreciable strength with time but doubling the cement did not double the unconfined compressive strength. Triaxial testing was then conducted on Mix 1 using specimens that were not flushed or saturated. This testing was used to determine if flushing destroyed the specimen soil fabric. The shear strength parameters from the triaxial testing were very similar to those determined from consolidated undrained testing. This demonstrated that flushing did not affect the shear strength parameters. Inconsistent triaxial test results from fly ash-cement-sand mixes have been previously reported in the literature.

Airborne Light Detection and Ranging (LIDAR) technology has become the primary method to derive high-resolution Digital Terrain Models (DTMs), which are essential for studying Earth’s surface processes, such as flooding and landslides. The critical step in generating a DTM is to separate ground and non-ground measurements in a voluminous point LIDAR dataset, using a filter, because the DTM is created by interpolating ground points. As one of widely used filtering methods, the progressive morphological (PM) filter has the advantages of classifying the LIDAR data at the point level, a linear computational complexity, and preserving the geometric shapes of terrain features. The filter works well in an urban setting with a gentle slope and a mixture of vegetation and buildings. However, the PM filter often removes ground measurements incorrectly at the topographic high area, along with large sizes of non-ground objects, because it uses a constant threshold slope, resulting in “cut-off” errors. A novel cluster analysis method was developed in this study and incorporated into the PM filter to prevent the removal of the ground measurements at topographic highs. Furthermore, to obtain the optimal filtering results for an area with undulating terrain, a trend analysis method was developed to adaptively estimate the slope-related thresholds of the PM filter based on changes of topographic slopes and the characteristics of non-terrain objects. The comparison of the PM and generalized adaptive PM (GAPM) filters for selected study areas indicates that the GAPM filter preserves the most “cut-off” points removed incorrectly by the PM filter. The application of the GAPM filter to seven ISPRS benchmark datasets shows that the GAPM filter reduces the filtering error by 20% on average, compared with the method used by the popular commercial software TerraScan. The combination of the cluster method, adaptive trend analysis, and the PM filter allows users without much experience in processing LIDAR data to effectively and efficiently identify ground measurements for the complex terrains in a large LIDAR data set. The GAPM filter is highly automatic and requires little human input. Therefore, it can significantly reduce the effort of manually processing voluminous LIDAR measurements.

Många infrastrukturprojekt involverar byggnation i berg där det alltid finns osäkerheter att hantera, dessa kan minskas genom att utföra fler undersökningar. Eftersom förundersökningar i berg är relativt dyra gäller det att hitta en balans där fältprogrammet är ekonomiskt försvarbart. Ett området som studerats det senaste åren är att utreda kostnadsnyttan som förundersökningarna tillför. Metoden som har utvecklats kallas datavärdesanalys och används för att kunna bedöma kostnadsnyttan av att utföra ytterligare förundersökningar innan de är utförda. Syfte med studien är att utvärdera kostnadsnyttan av ytterligare förundersökningar för en injekterings- och bergförstärkningsdesign i ett riktigt bergbyggnadsprojekt. Detta kommer att göras med en utvecklad statistisk metod av datavärdesanalysen.  Förväntade resultat från studien var: Undersöka hur insamlad data från tidigare förundersökningar i projektet kan användas för att bedöma sannolikheterna i datavärdesanalysen. Utveckla datavärdesanalysen för att vara tillämpbar i ett bergbyggnadsprojekt. Testa metoden i ett byggprojekt med riktig data och kostnader. Utvärdera om den framtagna metoden är tillämpbar i ett bergbyggnadsprojekt. I studien upprättades först två olika typdesigner för injekteringen och bergförstärkningen, baserat på en begränsad mängd data som fanns tillgänglig för en utvald sektion (fall 1). Mängden data som var tillgänglig i fall 1 är liknande som i en förstudie. Sedan upprättades två nya typdesigner för vardera område där kompletterande information från högkvalitativ data från kärnborrhål, hammarborrhål och vattenförlustmätning adderades (fall 2). Sannolikheterna i datavärdesanalysen bedömdes genom att använda en statistik metod. Den statistiska metoden baserades på en monte carlo simulering där stupningen på brottet antogs variera för bergförstärkningen och konduktiviteten antogs variera för injekteringen.  Studien påvisade goda resultat för att datavärdesanalyser skulle kunna implementeras i projekt som ett beslutsunderlag. Problematiken som kan uppstå i projekt där man har olika åsikter om hur mycket förundersökningar som behövs skulle kunna elimineras genom att använda datavärdesanalyser på den tillgängliga informationen samt nyttan av mer information. Detta är viktigt ur ett samhällsekonomiskt perspektiv. Det är dock viktigt att personen som använder verktyget förstår hur metoden är uppbyggd och dess antaganden. Gör man inte det finns det stor risk att beslut fattas på grund av felaktigheter som kan finnas i både indata och misstolkad utdata. Vidare rekommenderas att metoden utvecklas innan den används i ett riktigt projekt. Exempel på detta kan vara att göra mindre antaganden. Det kan också vara att försöka koppla datavärdesanalysen till var man har utfört undersökningen på sträckan man studerar. Man skulle även kunna inkludera fler parametrar i sin monte carlo simulering. Slutligen kan man, för att göra metoden mer användarvänlig, skapa en bättre plattform som den kan användas på. / Many infrastructure projects involve construction in rock, where there are a lot of uncertainties to deal with. These uncertainties can be reduced by performing preliminary investigations. Since preliminary investigations are expensive, it is necessary to find a balance where the field program is financially justifiable. In recent years cost-benefit analysis has been studied to investigate the benefits that preliminary investigations add. The method that has been developed is called value of information analysis and it assesses the cost-benefit of doing more investigations before they are performed.  The purpose of this report is to evaluate the benefits of additional preliminary investigations in a real project that could improve the grouting and rock support designs. The studied method is VOIA (Value of Information Analysis) based on statistical probabilities. The expected result of the study was: Investigate how collected data from preliminary investigations can be used to determine the probabilities used in the VOIA concept based on statistics. Develop a VOIA concept that is based on statistics and can be applied in a real project. Test the concept in a real project with real data and costs. Evaluate however the statistical approach was suitable to be applied in a real project. First part of the study consists of establishing two basic designs for grouting and rock support, that is based on a limited amount of information for a certain section of the project (case 1). The data available in case 1 is similar to a desk study. For the second part of the study the previous designs were updated and adjusted according to the additional information, from high quality investigations such as core drilling and water pressure test (case 2). The probabilities in the value of information analysis were evaluated using a statistical approach. The method was based on a monte carlo simulation where the dip of the plane was assumed to vary for the reinforcement design. For the grouting design the conductivity was assumed to vary.   Conclusions from this report proves that a statistical approach for the VOIA concept has great possibilities of being applied in projects as a tool before making decisions regarding preliminary investigations. The problem that often occur in projects today concerning different opinions about the amount of investigations needed, could be eliminated if a well constructed statistical model can be used that has the possibility of adjusting to the amount of available data. This would be beneficial from a socioeconomic perspective. However it's important that the user of this approach understand the purpose of every assumption and understands how to interpret the output data. Otherwise, decisions can be based on errors made by assumptions or bad input data.   Furthermore, recommendations is presented in this report regarding some areas that need to be developed before it is suitable to apply the method in a real project. One is to construct the VOIA concept based on fewer assumptions. Another is to connect the VOIA method to the geographical point of where the investigations have been made. There is also a possibility to include more parameters in the monte carlo simulation. Finally, to construct a more applicable tool in a project, a user friendly platform to conduct the analysis from is a great area to develop.

A Finite Element Analysis (FEA) investigation of concrete tunnel systems traversing seismic faults is carried out to determine how to effectively mitigate the stresses induced in the liner when subject to fault displacement. A parametric study of various fault parameters, both in the damage zone and competent rock, is carried out to determine the site conditions which induce the most stress on the tunnel liner system. Results indicate that friction angle, cohesion, and elastic modulus of fault zones have varying effects on the stresses induced on the liner. The width of damage zone and expected displacements are also investigated and it has been shown that even small displacements over narrow damage zones, around 10 m, can still result in significant damage to the concrete liner whereas in wider damage zones the effects of the displacement are more evident. The use of flexible joints in what is known as the articulated design method is investigated to mitigate the stresses induced by fault displacement and discussed. Several orientations, lengths and variations in relative stiffness of these flexible joints are investigated to determine their optimal effectiveness. Results show that this is an effective solution which can be used in design and repair of tunnels to mitigate the stresses and resulting damages to concrete tunnel liners subject to fault displacement.

Detta examensarbete är en introduktion till ämnet transversalbelastade pålar i kohesionsjord. Rapportenbehandlar teorin kring transversalbelastning, bäddmodul och gruppeffekt av pålar i lerjord. Trepublicerade rapporter där experiment av transversalbelastning av pålar i lerjordar har dokumenterats i detta examensarbete. Rapporten innehåller även experiment av transversalbelastning av stålrörpålar i Göteborg. I experimentet har en varmvalsad kvadratisk stålrörspåle samt två cirkulära, längsgående svetsade stålrörspålar, provbelastats. Den kvadratiska och en av de cirkulära stålrörspålarna har instrumenterats med trådtöjningsgivare längst hela utsidan av pålen. Alla tre pålar instrumenterats med inklinometerrör i översta 6m av pålarna. Pålarna installerades med hjälp av grävmaskin utrustad med högfrekvent vibrator. Som mothåll installerades tre spontplankor med längd på 10m med och en total bredd på cirka 2 meter. Efter installation tilläts leran konsolidera i cirka fyra månader. Samtliga pålar belastades i laststeg där magnituden av belastning mättes med hjälp av lastcell. Mätningarna av påltopparnas förskjutning gjordes med hjälp av mätklocka som fästes på en referensbalk bakom pålarnas förskjutningsriktning. Deformationen mot djupet mättes med inklinometer före och efter varje laststeg. Referensbalken och mothållets förskjutning mättes in med hjälp av mätprismor före och efter belastning av respektive påle. Ingen av töjningsgivarnaöverlevde installationsprocessen och konsolideringstiden. Flertalet problem har uppstått under fältförsöket där pålar behövts kapats, töjningsgivare skadats och inklinometerrör lossnat. I slutändan kunde inga töjningsgivare mätas på någon av pålarna. Inklinometermätningar var möjlig de översta 4m i båda cirkulära pålar och 6m i den kvadratiska pålen. Analysdelen i detta examensarbete är begränsat då fokus legat på fältförsöken. Analytiska beräkningar har utförts för en jordprofil bestående av ren lera. De analytiska beräkningarna är gjorda enligt Handboken Bygg Geoteknik och bärförmågan av stålrörspålarna kontrollerats enligt Eurokod 3. De analytiska beräkningarna består av spänning-, tvärkraft- och momentfördelning samt lutningsvinkel och horisontell deformation längst djupet för respektive tvärsnitt. De analytiskaberäkningarna är gjorda med fyra olika bäddmoduler. En känslighetsanalys för att undersöka vikten av korrekt indata har gjorts. Resultatet visade att de analytiska beräkningarna överskattar styvheten i leran avsevärt vid maximal last. Förskjutningarna som uppmättes vid fältförsök var avsevärt större än de som beräknats. Förskjutningen vid fältförsöket var plastiska redan vid små laster. De analytiska beräknade förskjutningarna stämmer relativt väl vid små laster. Vidare studier behöver göras för att få bättre förståelse av jordens kapacitet. VKR-pålen verkar avsevärt styvare jämfört med de två cirkulära stålrörspålarna.

An investigation was conducted to determine the response of landfills to the operation of a vertical ground source heat pump (i.e., heat extraction system, HES). Elevated landfill temperatures, reported various researchers, impact the engineering performance of landfill systems. A numerical model was developed to analyze the influence of vertical HES operation on landfills as a function of climate and operational conditions. A 1-D model of the vertical profile of a landfill was developed to approximate fluid temperatures in the HES. A 2-D model was then analyzed over a 40 year time period using the approximate fluid temperatures to determine the heat flux applied by the HES and resulting landfill temperatures. Vertical HES configurations simulations consisted of 15 simulations varying 5 fluid velocities and 3 pipe sizes. Operational simulations consisted of 26 parametric evaluations of waste placement, waste height, waste filling rate, vertical landfill expansions, HES placement time, climate, and waste heating. Vertical HES operation in a landfill environment was determined to have 3 phases: heat extraction phase, transitional phase, and ground source heat pump phase. During the heat extraction phase, the heat extraction rate ranged from 0 to 2550, 310 to 3080, and 0 to 530 W for the first year, peak year, and last year of HES operation, respectively. The maximum total heat energy extracted during the heat extraction phase ranged from 163,000 to 1,400,000 MJ. The maximum difference in baseline landfill temperatures and temperatures 0 m away from the HES ranged from 5.2 to 43.2°C. Climate was determined to be the most significant factor impacting the vertical HES. Trends pertaining to performance of numerous variables (fluid velocity, pipe size, waste placement, waste height, waste filling rate, vertical landfill expansions, HES placement time, climate, and waste heating) were determined during this investigation. Increasing fluid velocity until turbulent flow was reached increased the heat extraction rate by the system. Once turbulent flow was reached, the increase in heat extraction rate with increasing fluid velocity was negligible. An increase in the heat extraction rate was caused by increasing pipe diameter. Wastes placed in warmer months caused an increase in the total heat energy extracted. Increasing waste height caused an increase in the peak heat extraction rate by 43 W/m waste height. Optimum heat extraction per 1 m of HES occurred for a 30 m waste height. Increasing the waste filling rate increased the total heat energy extracted. Heat extraction rates decreased as time between vertical landfill expansions increase. Total heat energy extracted over a 35 year period decreased by approximately 21,500 MJ/year for every year after the final cover was placed until HES operation began. For seasonal HES operation, the total heat energy obtained each year differs and the fourth year of operation yielded the most energy. Wet Climates with higher heat generating capacities yielded increased heat extraction rates. Maximum temperature differences in the landfill due to the HES increased by 16.6°C for every 1 W/m3 increase in peak heat generation rate. When a vertical HES was used for waste heating, up to a 13.7% increase in methane production was predicted. Engineering considerations (spacing, financial impact, and effect on gas production) for implementing a vertical HES in a landfill were investigated. Spacing requirements between the wells were dependent on maximum temperature differences in the landfill. Spacing requirements of 12, 12, 16, and 22 m are recommended for waste heating, winter-only HES operation, maximum temperature differences in the landfill less than 17°C, and maximum temperature differences in the landfill greater than 17°C, respectively. A financial analysis was conducted on the cost of implementing a single vertical HES well. The energy extracted per cost ranged from 0.227 to 0.150 $/MJ for a 50.8 mm pipe with a 1.0 m/s fluid velocity and a 50.8 mm pipe with a 0.3 m/s fluid velocity, respectively. A vertical HES could potentially increase revenue from a typical landfill gas energy project by $577,000 per year.

The effectiveness of removing anomalous material from cast-in-drilled-hole (CIDH) piles by water jetting was examined. The primary objectives of this research were to examine how reinforcing steel influences water jetting and to evaluate how jetting pressures and standoff distance from the material surface affect water jetting of concrete type materials and PVC tubing. The experimental work consisted of water blasting submerged test specimens using rotary jets, nozzles, pumping equipment, and testing procedures currently used in construction practice. The concrete test specimens were comprised of ring- and cylinder-shaped samples, containing materials with compressive strengths of approximately 160 and 3,600 psi. Typical PVC tubing used as inspection access holes for non-destructive testing in CIDH piles was utilized for tubing specimens. During testing, erosion depths were measured as a function of standoff distance and jetting pressure. Water jetted specimens containing reinforcing steel were cut apart after testing to permit inspection of the erosion cavity and eroded material surfaces behind the steel reinforcement. Reinforcing steel bars in CIDH piles do interfere with the jet path and will locally influence material erosion and water-jetting effectiveness. For a relatively weak material, water-jetting pressures between 10,000 and 11,000 psi produced erosion up to a radial distance of approximately 12 inches from the water jet. This erosion distance is less than half the typical maximum design spacing of PVC inspection access tubing installed in CIDH piles.

An investigation was conducted related to the dimensional stability of geosynthetic clay liners (GCLs) in landfill applications. Multiple occurrences of panel separation of overlap seams in GCLs have been documented; however, explanation for the relative contribution of various mechanisms causing shrinkage has been limited. A systematic test program was conducted to determine the effects of a variety of conditions on GCL dimensional stability. Effects of initial moisture content, permeant type, and overburden pressure were tested by subjecting various GCL products to wet-dry cycles and measuring the dimensional change with each cycle. Different GCL types were each tested under various combinations of initial moisture content (as-received, 50, 75, 100, and 125%), permeant types (tap water, distilled water, and 0.1 M CaCl2), and overburden pressures (0, 6, and 20 kPa). Thermal expansion tests were conducted by heating or cooling GCL test specimens to temperatures of 0, 10, 40, 60, and 80°C at constant moisture content. Subgrade tests were conducted by placing GCL test specimens on compacted clay and sand subgrades in different orientations and hydration conditions in sealed containers and measuring dimensional change over time. Mechanical necking tests were conducted by subjecting GCL specimens to varying levels of tension and measuring the longitudinal and transverse strains at each load increment. Field simulation tests were conducted by placing specimens on a compacted sand subgrade beneath an exposed geomembrane liner outdoors in late summer. Initial moisture content tests resulted in shrinkage strains as high as 20% after 20 wet-dry cycles. GCLs ranged from slightly anisotropic [approximately 1.1:1 ratio of machine (MD) to cross-machine (XMD) shrinkage] to highly anisotropic (approximately 3:1 ratio of MD to XMD shrinkage). Most combinations of GCL type and initial moisture content resulted in GCL MD shrinkage strains greater than a value that would cause panel separation (termed panel separation threshold, PST) at roll ends during the first wet-dry cycle. All test specimens contracted beyond the PST in the MD within 3 wet-dry cycles. GCL specimens without attached geomembranes contracted beyond the PST in the XMD within 5 cycles. Permeant type tests demonstrated that hydration with 0.1 M CaCl2 reduced shrinkage by 50-80% compared to permeation with tap water. Overburden tests demonstrated that applying 6 kPa and 20 kPa reduced specimen shrinkage by at least 60% and 80%, respectively. Thermal expansion tests indicated that temperature changes at constant moisture content had little effect on GCL dimensional stability. Subgrade tests demonstrated that subgrade type and moisture as well as GCL type and orientation had effects on dimensional stability. Tensile necking tests demonstrated that transverse shrinkage occurred due to tensile forces in GCLs, but shrinkage was nearly always less than PST. Field simulation tests demonstrated that wet-dry cycles in the field were less intense and/or less frequent than in the laboratory. Results of this testing provide a basis for GCL overlap specifications necessary to maintain full coverage and future research to confirm a suggested method of preconditioning bentonite to prevent shrinkage.

An extensive laboratory and field investigation was conducted at Santa Maria Regional Landfill (SMRL) in Santa Maria, CA to determine the effects of waste placement practices on the engineering response of municipal solid waste (MSW). Laboratory and field testing was used to determine the engineering properties and monitor field response of MSW. The specific gravity (Gs) of manufactured MSW (MMSW), fresh MSW (FMSW), and old MSW (OMSW) was determined experimentally using a modified version of standard soil testing procedures. Effects of particle size, compactive effort, and degradation on the specific gravity of waste were evaluated. Specific gravity of manufactured waste samples increased with decreasing particle size, with compaction, and with increased degradation. The average specific gravity of uncompacted MMSW samples was 1.333, 1.374, and 1.424 for coarse, medium, and fine particle sizes, respectively. Specific gravity of coarse, medium, and fine MMSW samples compacted at dry of optimum (= 30%) was determined to be 1.497, 1.521, and 1.552, respectively and at wet of optimum ( = 90%) to be 1.500, 1.542, and 1.570, respectively. The compacted and uncompacted specific gravity of fresh MSW was lower than manufactured and old MSW. The average Gs of uncompacted and compacted fresh MSW was 1.072 and 1.208, respectively whereas old MSW had Gs of 2.201. Additional physical and engineering properties of MSW were determined for fresh and old wastes. A total of 8 magnetic extensometer settlement arrays and 4 thermocouple arrays were installed in old wastes. The settlement and temperature data were collected for an approximate duration of 1 year. In addition, laboratory experiments were conducted to determine the particle size distribution, organic content, and moisture content of fresh waste sampled from the active face of the landfill and from old waste sampled from different depths. The particle size distribution of OMSW was comparable to a well-graded coarse-grained soil. The average baseline moisture content of incoming MSW at SMRL was 42.7% (dry-weight basis). The average moisture content of residential MSW, commercial MSW, and self-delivered MSW were determined to be 57.7, 46.3, and 12.0%, respectively. The organic content of fresh and old MSW was determined to be 77.2 and 23.5%, respectively. Temperature increased over time due to heat generation of the waste mass. The temperature increased on average 3 to 6°C between the initial and final day of measurements for wastes that were 0.3 to 9 years old. Fresh and old wastes at SMRL exhibited unique compression behavior. A majority of the waste was undergoing secondary compression characterized using a secondary compression ratio () ranging from 0.013 to 0.067 with an average of 0.030. In addition, the fresh and old wastes exhibited recompression behavior. Fresh waste lifts were determined to be slightly overconsolidated such that the self-weight of the fresh waste was less than the preconsolidation stress. The old waste exhibited recompression behavior during loading and unloading of an earthen embankment. The modified recompression indices () for fresh and old wastes were determined to be 0.076 and 0.012, respectively. The initial compression ratio for old wastes () was quantified for the old waste lifts to be between 0.069 and 0.332. Finally, meso- and full-scale field compaction experiments were conducted to determine the effects of systematic moisture addition prior to compaction on placement efficiency and compaction characteristics of MSW. Two 16 x 46 m test plots were constructed for the meso-scale compaction tests. Approximately 890 kN (100 tons) of residential MSW (RMSW) was placed into a test plot and compacted at target moisture contents of 55 (baseline as-received), 65, 80, 95, and 110%. Compaction curves generated for RMSW were bell shaped and similar to soil compaction curves. The maximum dry unit weight () and operational unit weight () for the meso-scale compaction study were 8.5 and 13.3 kN/m3 with corresponding optimum moisture contents of and , 78.5 and 79.5%, respectively. Moisture addition prior to compaction yielded beneficial waste placement results. An operational waste placement factor (OWPF) was defined as additional amount of waste that could be placed in one unit of volume. OWPF values were determined to be 1, 1.33, 1.66, 1.37, and 0.83 for RMSW compacted at target moisture contents of 55, 65, 85, 90, and 110%, respectively. The full scale compaction investigation was conducted in a similar manner to the meso-scale investigation. However, the compaction tests were conducted on the active face of the landfill and representative of the entire incoming daily waste stream. A daily average of 2940 kN (330 tons) of MSW was placed and compacted at target moisture contents of 45 (baseline as-received), 65, 85, and 105%. Compaction curves for the delivered MSW were bell shaped and similar to soil compaction curves. The maximum dry and operational unit weights for the full-scale test were 7.0 and 9.8 kN/m3, respectively corresponding to optimum moisture contents of and , 76 and 75.5%, respectively. OWPFs were calculated to be 1, 1.28, 1.55, and 0.80 for target moisture contents of 45, 65, 85, and 105%, respectively. The spatial variability associated with moisture addition also was determined for the meso- and full-scale compaction tests and verified using test pits and spatial sampling of the surface of the active face. Particularly, the variations in degree of saturation (S) and volumetric moisture content () due to moisture addition were estimated. For waste compacted at target moisture contents of 55, 65, 80, and 110% during the meso-scale tests, S increased by 19, 4.5, 4.4, and 4.3%, respectively while increased by 28, 7.7, 8.1, and 5.7%, respectively. For the full scale compaction tests, S increased by an average of 43% and increased by an average of 78%. The average moisture content of waste at the surface after compaction at 45% moisture content (i.e., as-received) and at 80% moisture content (i.e., near optimum) were 34 and 133%, respectively. The results of the investigation have environmental, operational, and financial implications such as extend the life of a landfill, ability to place more wastes in a unit landfill volume, and increasing to values above field capacity with moisture addition during compaction.