abstract: This study evaluates the use of plant-extracted silica solution as a bio-based grout material for improvement of granular soils. Although silicate grout is a very well-established and popular technique in the ground improvement market, efforts have been initiated to replace chemically-synthesized silicate grout with plant-extracted silica grout. This initiative will increase the level of sustainability and consequently improve the existing market acceptability. The silica-rich plant source used for extraction was rice husk, which is an abundantly produced agricultural waste. The extraction method includes acid-leaching, temperature-controlled rice husk ash production and the preparation of an aqueous sodium silicate solution from the ash through an alkaline leachate method. Silica ash was in amorphous form containing 95% of silica content which is suitable for soil treatment. Gelation time was controlled in the absence and presence of sand under different pH values. Bio-based silica grouting showed an improvement of the shear strength of the soil as well as the hydraulic conductivity reduction. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2019

A today common soil reinforcement method is the installation of lime-cement columns. Lime-cement columns have been used since the 1970’s and have been a useful method for stabilizing soil at great depths. It is mostly used for stabilizing road and railway embankments because the method is economically viable and the columns are easy to install. The total costs for the installation of the lime-cement columns is dependent on the numbers of installed columns, what percentage of lime and cement that has been used and the pattern in which the columns has been installed. It has been found that the method is more preferred from an environmental perspective than other stabilizing methods from a transport and pollution point of view. A problem with the installation of lime-cement columns is that the stability of the columns has been varying, and that has contributed to costly quality controls. In many cases has a higher security factor than necessary been used, leading to more costs. In this master thesis it has been evaluated whether is exists a relationship between the soils initial undrained shear strength and the evaluated shear strength of the lime-cement column reinforced soil. If such a relationship can be proved, the initial test of the soil might contribute to an easier estimation of how the strength in the columns will develop. It might also contribute to simplify the estimated quantity of the binder and facilitate the estimation of where the tests will be executed. By using different probing and samplings results, the undrained shear strength and other parameters have been evaluated in about 50 sampling points. These have been compared to the shear strength in about 150 lime-cement columns along the new E45 between the cities Bohus and Nödinge in the south of Sweden. The area has been divided into 5 parts to see differences in the geographical areas. The lime-cement columns have been tested after 2 weeks and after 4 weeks after the installation to see the changes due to time. An analysis of how the shear strength in the columns is dependent of the shear strength in the soil along with the depth has been made. The result indicates that the properties of the soil don’t vary significantly along the area, meaning that the differences in the results are dependent on the installation methods of the lime-cement columns and not by the changes in the soil. It can be concluded that the shear strength in the soil increases by the depth, which is a result of the increasing in-situ stress along with the depth. When analyzing the columns tested after 2 weeks it can be stated that there are no significant change of the shear strength along with the depth due to the increasing in-situ stress, and a week relationship could be seen when the columns had been tested after 4 weeks. The reason for this might be the impact of the hydration process meaning that the in-situ stress has a higher impact on the lime-cement columns by time. The variation of the shear strength in the lime-cement in columns with the depth along the distance is independent of the shear strength in the soil, as can be seen from the determination coefficient in the studied intervals that didn’t exceed 10 % with reservation for a few misleading results. The geographical placement has a negligible impact on the lime-cement column-complex.

The precipitation system CIPS (Calcite In-situ Precipitation System) has been created as a permeation grouting system based on a two component fluid with the intention of slowly permeate and fill the pores. It causes cementation through a chemical reaction which bonds the soil particles together at the contact points. CIPS mimics one of the natural reactions in nature where sandstone is formed through calcite precipitation. This system is used in Australia with excellent results and there are many factors governing the outcome of the method, some of these factors are: flow rate, pressure, time, chemical recipe, temperature, composition of the soil matrix and number of performed injections at the same point of location. Some of these factors have been the focus of this report and where they have been examined from a Scandinavian point of view where our ground temperature conditions and soil compositions have governed the outcome of the accomplished results. The strength increase has been examined through laboratory tests where natural sand from a building site with known particle size and dry density has been treated once with the CIPS Fluid. This treatment was completed in a temperature controlled room of 12 degrees after which the treated soil was tested by unconfined compression tests. Even a rather low increase in bearing capacity of the soil would result in benefits during the construction of temporary constructions during the early building stages foundation work. Since the desired increase in bearing capacity of the soil is fairly low, 50-100 kPa, the investigations has concentrated on one single injection, in order to study if there is a clear trend in the increase in bearing capacity, and if it can be roughly predicted. In addition to the above mentioned laboratory work a small scale field test has been conducted, where the CIPS Fluid was injected into the ground with the aim of creating a column shaped object. This column was left for a certain time, a time long enough for the calcite crystal to bond the soil grains and generate an increase in strength. When the assumed cementation had occurred an ocular assessment was carried out in order to predict whether the strength had increased or not, and to what degree. Based on the laboratory results, some evidence of that strength increase occurs due to either the discharge of the spent fluid containing ammonium chloride or the process of drying. Either way, the strength increase takes place during the grounds natural process of adjusting towards the natural water content equilibrium for the specific site of interest. A strength increase at the laboratory experiments of between approximately 60-220 kPa has been achieved. The field tests where slightly less rewarding when difficulties of injecting the CIPS Fluid into the sandy soil arose due to challenging task of designing a pumping system where both a low pressure, less than the overburden pressure, and a low flow rate, less than 7 litres per minute, could be controlled. The flow rate could be controlled but with the effect of the pressure rising to too high levels. Due to the observations of CIPS Fluids exiting the ground at other points than near the injection spear, soil fractures are assumed to have occurred at one ore many locations. The volumes treated with CIPS Fluid displayed no increase in strength as long as they appeared somewhat wet with the spent fluid. When this fluid containing ammonium chloride vanished from the treated soil and the pH-value dropped, the build up in strength through calcite crystallisation at the contact points began. This crystallization which leads to a cementation was observed at the centre of the small spheres achieved through injection in the ground, which proves that the Calcite In-situ Precipitation System has caused a cementation of the soil grains treated.

Ground improvement by deep mixing (DM) is a generic term used for a number of methods in which a binding agent, often lime and/or cement, is mechanically mixed with the soil to increase its engineering properties. The inherent variability with respect to the engineering properties of the improved soil is high due to the variations in geology and the complex mixing process. High variability introduces uncertainty in estimating improved soil properties and the performance of the structure. Current design methodology deals with soil properties deterministically and the uncertainties involved are incorporated in a single value represented by a total factor of safety (FS). The chosen FS is highly dependent on the engineer’s judgment and past experience, in which both of these factors vary between different geotechnical designers. Therefore, current design methodology used in practice for DM does not deal with uncertainties in a rational way. In order to design a geotechnical system with the desired level of confidence, the uncertainties involved must be integrated in the DM design. This can be achieved by using reliability-based design (RBD) methods. The research work in this thesis is presented as a collection of three papers. In the first paper, a comprehensive statistical analysis of cone penetration test (CPT) data is described. The objective was to make a contribution to empirical knowledge by evaluating the strength variability of lime-cement columns within the group of tested columns. In the second paper, the effect of the spatial variability and statistical uncertainty with regard to the embankment’s reliability was investigated within the framework of RBD. The study in the third paper investigated the strength variability in lime-cement columns based on two test methods, namely CPT and column penetration test (KPS). In this study, the effect of different test methods on the evaluation of the design value was addressed. The main conclusions from this study can be summarized as follows. First, the probability distribution function (PDF) for the undrained shear strength of lime-cement columns can be modeled in RBD as normal or log-normal distributions. However, the use of log-normal distribution is recommended for RBD analyses. Second, the evaluated scales of fluctuation indicate ranges of 2 to 4 m and 0.2 to 0.8 m in the horizontal and the vertical directions respectively. This means that in order to fulfill the requirements of independent/uncorrelated samples for assessment of the design value, the spacing between samples must exceed the horizontal scale of fluctuation. It is therefore proposed that the spacing between individual samples should be at least 4 meters. Third, the design values evaluated using CPT and KPS were approximately the same. However, the inherent variability evaluated differs due to the larger volume tested with the KPS probe than with the CPT probe. However, this difference was not significant between the two tests. Fourthly, due to the limitation in the deterministic design in terms of dealing with uncertainties, it is recommended that RBD design should be used in parallel with the deterministic design of lime-cement column. / <p>QC 20120110</p>

Lime-cement columns have been used in Sweden to improve poor soil conditions since the 1970’s. The method is inexpensive and flexible, but is difficult to test since the columns are manufactured in-situ. Many test-methods have been developed for testing the column strength during the years. Most of them need to be evaluated using an empirical correction-factor known as the cone factor. The column penetration test, KPS, is the most commonly used method in Sweden, it is considered to be reliable since a large part of the column cross-section is tested. The problem is that the probe easily deviates out of the column to the softer surrounding soil. Today a pre-drilled guiding-hole, a soil-rock sounding, helps the probe to stay vertical. Although the soil-rock sounding is commonly not used for evaluation of column strength, the penetration resistance is recorded. A visual comparison between the plotted penetration resistances from the two methods shows similarities in both hard and soft areas of the columns. The relation can be measured using statistics, such as the correlation coefficient. A strong correlation was also found, suggesting that a similar equation used to evaluate the undrained shear strength from the column penetration tests can be applied with the data from the soilrock soundings. The statically pushed column penetration test probe and the rotated soil-rock sounding bit bore are likely to cause different failure modes in the column. This means that different empirical cone factors are needed when the undrained shear strength is evaluated. By evaluating the ratio between the cone factors of the column penetration test and the data from the soil-rock soundings from three sites, E-road E18 north of Stockholm, E-road E45 outside Gothenburg and at a construction site at Lidingö, the following aspects of the ratio was investigated: if the ratio was site-specific; the sensitivity to the binder content; the sleeve friction and; the sensitivity to rotational speed and rate of penetration. Average columns formed from the penetration resistance at depth from each site were used during the evaluations. The Swedish geotechnical society has standardised two methodologies that can be used for pre-drilling. The soil-rock sounding methodology which has no fixed rate of penetration or rotational speed, and the total sounding methodology, based on the Norwegian total sounding methodology which has fixed rate of penetration and rotational speed. The latter is to prefer when comparing results between sites. To remove the sleeve friction, the data from the soil-rock soundings needed to be de-trended. The amount of de-trending needed to find a constant cone factor varied at the sites between 0.5 kN/m and 1.0 kN/m. This however caused high interference, partly from scaling the variation. The cone factor for the total sounding methodology was found to be between 0.30- 0.45 times the cone factor for the column penetration test.

Shallow Tunneling through highly populated areas of big cities is a challenging task. Almost in all the tunneling projects of shallow tunnel some or the other types of tunneling problems have been encountered and are still being faced. The stability of shallow tunnel is also influenced by many factors, primarily the in situ stress, geological structures, groundwater, rock mass quality, shape of tunnel etc. The design of shallow tunnel in past was almost purely a matter of experience. During last decays computational methods have been introduced as powerful design aids tool to arrive at safe and economical shallow tunnel structure. The purpose of this thesis work is to provide technical criteria and guidance for the design, and stability of Norra Länken shallow tunnel in rock for civil works projects. The design of shallow tunnels in highly dense areas is an iterative process. A good starting point is essential to the process and facilitates safe and economic design. Currently there are many practical two and three-dimensional software tools available for carrying out the task. This master thesis provides an overview of a methodology being used by tunneling experts, which captures the three-dimensional essentials of tunnel behaviour with two-dimensional analysis tools, PLAXIS. Though it is not a full and final situation and conclusion, but there is a lot to learn from such conditions .

Background: Restrictions on induced abortion varies widely across the globe and so does the rate of induced abortion and maternal mortality (MM). Safe abortions – done by trained providers in hygienic settings and early medical abortions carry fewer health risks and reduce maternal mortality rates (MMR). However, nearly 7 million women in developing countries are treated for complications from unsafe abortions annually, and at least 22,000 die from abortion-related complications every year. Aim: The aim was to explore national and regional patterns of abortion laws, the abortions percentages and the maternal mortality rates (MMR), to see if patterns could be distinguished and how they differentiate to each other. Method: With a shape-file containing polygons representing the world’s countries, and the computer program ArcMap, was used to gather and join data. Result: The result showed that many African countries has a restrictive abortion law, and they also have a high MMR. In the Nordic countries they have a liberalized abortion law and they have low MMR. Another finding is that a restricted abortion law does not correspond to a low percentage of abortions. This is clearly demonstrated in South America, where they have a high abortion percentage, and extremely restricted abortion laws. Conclusion: This result revealed patterns showing that countries with restricted abortion laws, does not contribute to a low MMR, and restricted abortion law does not decrease the percentage of abortions.

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The development in society means that infrastructure like ballasted railway systems are facing challenges due to request for increased number of high-speed trains and heavier freight trains. This implies that ballasted railways get an increased impact from larger dynamic loads. The question is how the ballasted railways are today affected by dynamic loading and how will an increase in train speed and weight change the soil behaviour within the railway embankment.  A method of investigating dynamic soil behaviour is via geophysical measurements. Accelerometers are commonly used for vibration measurements and by installing them on trains are measurements possible to perform for complete railway sections. The knowledge of expected natural frequencies for various track components and soil layers are essential when considering frequency based analysis of vibration measurements. Thus, a frequency based analysis of accelerometer measurements from track recording coaches enables a possible method for analysing the impact of dynamic loads on underlying soil materials with means of a knowledge of expected natural frequencies for various track components and soil layers. Importance to study frequency content of ground motions became more relevant after the Mexico City earthquake 1985 i.e. studies on this specific earthquake revealed amplification of ground motions due to a long duration of shaking and resonance of soil deposits and furthermore causing damage to buildings whose natural period was the same as the period of ground motion. Thus, if we consider a railway with long train sets running along the railway line. Long durations of shaking of the ground can occur as well as a possible resonance of various soil layers leading to changes in material properties. An interesting finding regarding vibration measurements conducted on a track recording coach show that after Fast Fourier Transformation of the measured vibration data, a frequency spectrum analysis indicate possibilities to detect resonance of the ballast layer in the railway embankment. Therefore, this thesis focus on frequency based analysis of the ballast layer were indications of changes in shear modulus of ballast is seen with means of frequency spectrum and theoretical knowledge of the change in shear modulus in ballast material under cyclic loading and increased shear strain. The thesis consists of two main parts, first is the construction of the so-called frequency-based analysis method of track alignment measurements in a geodynamic perspective and the second part is application of the frequency-based method on a case study. Thus, the scientific contribution of this thesis is to increase knowledge of track alignment measurements in the geotechnical field and to provide a frequency based analysis method of track alignment measurements in a geodynamic perspective for evaluation of soil properties. For the actual case study two different railway sections in Sweden is chosen to enable a comparison, especially when these sections differ with respect to one having only a ballast layer and subgrade and one having ballast, sub ballast and subgrade. Thus, the section with only ballast and subgrade enable a clearer analysis since these layers have large difference in natural frequency. First section is located at Tolikberget in the north part of Sweden and second one between Stenkumla and Dunsjö in south of Sweden. From the analysis of the selected sections it is possible to see indications from the frequency spectrum that the vibration measurements capture the natural frequencies of ballast material associated to the maximum shear modulus and to varying degrees of reduced shear modulus due to increased shear strain. Thus, it can be concluded that vibration measurements conducted on track recording coaches have potential to be used for studies of changes in ballast materials dynamic properties.

Global challenges associated with extreme climate events and increasing energy demand require significant advances in our understanding and predictive capability of coupled multi- physical processes across spatial and temporal scales. While classical approaches based on the mixture theory may shed light on the macroscopic poromechanics simulations, accurate forward predictions of the complex behavior of phase-changing geomaterials cannot be made without understanding the underlying coupling mechanisms among constituents at the microstructural scale. To precisely predict the multi-physical behaviors originated by smaller scales, fundamental understandings of the micromechanical interactions among phase constituents are crucial. Hence, this dissertation discusses mathematical and computational frameworks designed to capture coupled thermo-hydro-mechanical-fracture processes in phase-changing porous media that incorporate necessary microscopic details. To achieve this goal, this dissertation aims to introduce a practical way to investigate how phase transition and evolving microstructural attributes at small scales affect the applicability of meso- or macroscopic finite element simulations, by leveraging the phase field method to represent the regularized interfaces of phase constituents. Firstly, a multi-phase-field microporomechanics model is presented to model the growth and thaw of ice lenses. In specific, we extend the field theory for ice lens that is not restricted to one-dimensional space. The key idea is to represent the state of the pore fluid and the evolution of freezing-induced fracture via two distinct phase field variables coupled with balance laws, which leads to an immersed approach where both the homogeneous freezing and ice lensing are distinctively captured. Secondly, a thermo-hydro-mechanical theory for geological media with thermally non-equilibrated constituents is presented, where we develop an operator-split framework that updates the temperature of each constituent in an asynchronous manner. Here, the existence of an effective medium is hypothesized, in which the constituents exhibit different temperatures while heat exchange among the phases is captured via Newton’s law of cooling. Thirdly, an immersed phase field model is introduced to predict fluid flow in fracturing vuggy porous media, where crack growth may connect previously isolated voids and form flow conduits. In this approach, we present a framework where the phase field is not only used as a damage parameter for the solid skeleton but also as an indicator of the pore space, which enables us to analyze how crack growth in vuggy porous matrix affects the flow mechanism differently compared to the homogenized effective medium while bypassing the needs of partitioning the domain and tracking the moving interface. Finally, we present a new phase field fracture theory for higher-order continuum that can capture physically justified size effects for both the path-independent elastic responses and the path-dependent fracture. Specifically, we adopt quasi-quadratic degradation function and linear local dissipation function such that the physical size dependence are insensitive to the fictitious length scale for the regularized interface, which addresses the numerical needs to employ sufficiently large phase field length scale parameter without comprising the correct physical size effect.