A laboratory-scale experimental investigation on the performance of lime columns in expansive Ankara (Turkey) Clay

Swelling of expansive soils and associated movements of foundations cause serious problems to many structures. With the existing expansive clays in Ankara, capital city of Turkey, some light buildings, road pavements and buried pipelines have shown some damage. To avoid such damage, prior to construction expansive clays may be stabilized. There has been little work concerning the stabilization of Ankara Clay and this was concentrated on the lime mixture technique. The main objective of this study was to investigate the performance of the lime column technique on laboratory-scaled models to improve the physical, swelling, strength and consolidation characteristics of this clay. The characteristics of the treated samples were determined in terms of distance to the column and curing period. In general, the results suggested that the most effective zone for the lime migration developed at a distance approximately twice the column diameter and a curing period of 28 days generally seemed to be sufficient. Application of the technique provided a gain in strength between 40 and 80% and resulted in an increase in pre-consolidation pressure and a decrease in the compressibility characteristics of the treated soils, depending on the distance to the lime column. Construction of the column caused a drastic reduction in swell pressure, between 40 and 75%. Electronic Publication     

Stabilization of clay soils using lime and effect of pH variations on shear strength parameters

This paper presents the results of geotechnical and mineralogical investigations on lime treated clay soils from Hamedan City, Iran, and effects of pH variations on their shear strength parameters. Initially, lime was added in different percentages and laboratory experiments were conducted after curing times. The results indicate that these soils can be stabilized satisfactorily with the addition of about 7 % lime. Also, investigation of the relationship between lime-treated geotechnical properties and lime percentage and curing time demonstrates high regression coefficients for the proposed relationships. Several laboratory tests were performed on treated and untreated clay soils with lime mixed with pore fluids with different pH values including 3, 5, 7 and 9. The results of shear strength tests indicated that the undrained shear strength parameters for untreated clays increased considerably if the pore fluid had a high pH (pH = 9) or a low pH (pH = 3). It can also be found that for lime-treated soils, maximum cohesion and friction angle values are achieved at pH = 9.     

Landfill site selection utilizing TOPSIS methodology and clay liner geotechnical characterization: a case study for Ankara,Turkey

The purpose of this study was to select alternative landfill sites for Ankara based on the growing trends of Ankara toward the Gölba?? municipality, and to eventually select the best alternative through the use of decision-making tools. Geographic information systems (GIS) and multi-criteria decision analyses were employed to perform landfill site selection. Several criteria, including geology, slope, proximity to roads, availability and proximity of landfill containment material, settlement, suitability for agriculture, vegetation cover, erosion, and lineament system were gathered in a GIS environment. A weight value was assigned to each criterion by applying the pairwise comparison method and the analytical hierarchy method. An ideal point method, namely, the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS) was applied to choose the best alternative landfill site. The geotechnical properties of “Ankara clay”, which shows widespread distribution in Ankara, were reviewed and assessed for the clay's suitability as a single, compacted clay liner and as a component of a geomembrane-compacted clay composite liner for the alternative landfill site selected. The HELP model was employed in order to determine the cumulative, mean leachate head and cumulative, unitized expected leakage rate amounts through the landfill. Four different profiles, from the least conservative to the most conservative, were created and analyzed.     

Utilization of a very high lime fly ash for improvement of Izmir clay

This paper presents an investigation into the stabilization of a soft clay subgrade of a military zone in Izmir, Turkey with a very high lime fly ash. Zero%, 5%, 10%, 15% and 20% (m/m) of the soil was replaced with fly ash. In addition to the control specimen, four different stabilized soil samples were prepared mixing fly ash with soil at optimum water contents determined by standard proctor test. Experiments lasted for 3 months and the unconfined compressive strength and shear strength parameters, cohesion and internal friction angle, were determined after 1, 7, 28 and 90 days. It was found that, inclusion of fly ash improved the properties of the soil. The improvements, appearing with increasing fly-ash content, were attributed to the pozzolanic reaction and pore refinement effect of fly ash as well as its high free-lime content.     

澧东公路高液限黏土改良及其施工工艺

以实际公路工程为依托,针对高液限黏土路的物理力学性质及工程特性,鉴于高液限黏土路基修筑中所面临压实性差、失水收缩开裂、稳定性差等问题,提出了高液限土作为回填土的改良方案及其施工工艺,以达到指导实践的目的。     

Remaining tree species from the indigenous vegetation of Ankara, Turkey

The city of Ankara is located in the geographic centre of Anatolia, Turkey. In the state of nature, Anatolia was covered with forests. Due to the destructive effects of civilisations passing through Anatolia over the centuries, the forest vegetation was gradually transformed to a steppe formation. After it became the capital city, a rapid planned urbanisation process was initiated in Ankara. In the first development plan, efforts were concentrated on the south axis of the city, which harbored the greatest concentration of indigenous plant cover in the valleys.In 1974, the embassy gardens and parks on the north–south axis were declared a “Natural Conservation Area”. Despite the conservation act, change and denuding of indigenous vegetation continued all along the axis due to highly increasing development. However, these conservation areas still include tree species from the indigenous vegetation. In this study, the presidency gardens, the embassy gardens and parks in Ankara that were declared a “conservation area” were evaluated in terms of the remaining tree species from the indigenous plant cover. The study aims to indicate the level of conservation of natural habitat in Ankara and to determine whether the concept of “Natural Conservation Areas” includes the protection of biodiversity or not. Moreover, the research results aim to reveal still existing tree species of indigenous vegetation, which will enlighten us regarding future landscape planning in Central Anatolia. Trees were examined by age, height and exposition. The results show that remaining indigenous tree species of the study area grow along the former ncesu River and that the terrain on which the trees stand is mostly exposed to the southwest and southeast. The indigenous tree species which do not exist in the study area are scattered in valleys along the river trails or on the hills of Ankara’s rural lands.     

无水石膏与高强石膏对低品位石膏增白的实验研究

采用无水石膏、高强石膏和增白填料对低品位石膏增白进行了实验研究。结果表明:将处理后的无水石膏与低品位二水石膏混合炒制后,制成的复合石膏白度由72.3%提高到75.5%、强度有所增加。在此基础上采用高强石膏与增白填料对复合石膏作进一步增白试验表明,可在提高复合石膏强度的同时使白度由75.5%提高到80.1%。     

Evaluation of small strain stiffness characteristics of soft clay treated with lime and nanosilica and correlation with UCS (qu)

Bulletin of Engineering Geology and the Environment - Improving the strength and stiffness properties of soils using non-conventional materials has been extensively performed in the past decade. In...     

Engineering geological evaluation and preliminary support design for the metro extension tunnel,Ankara, Turkey

The paper reports an assessment of the engineering geological characteristics of the rock mass to be encountered between Mecidiye and Gazino stations on the new extension of the Ankara metro and the determination of appropriate support and excavation methods. The rock mass quality was estimated using the rock mass rating (RMR), geological strength index (GSI) and rock mass quality (Q) systems and the tunnel divided into sections. The RMR, Q and NATM systems were used to determine the support and excavation methods in these areas. The deformations and stress concentrations around each tunnel section were investigated and the interaction of the support systems with the rock mass was analyzed using finite element software. It is concluded that rock mass classification systems should be used in tandem with numerical tools, although it is emphasized that the estimation of rock mass properties is not an exact science and both rock properties and numerical models should be refined based on observations and the results of instrumentation installed during the construction of a tunnel.      

Stability of soft clay soil stabilised with recycled gypsum in a wet environment

This study investigates the effect of the soaking condition in a wet environment on the stability and durability of soft clay soil treated with recycled gypsum. Cement and lime are the two types of solidification agents used to improve the durability of the clay–gypsum mixture and to reduce the solubility of the gypsum in a wet environment because gypsum is soluble in water. The recycled gypsum was mixed with cement and lime in different ratios in the dry state, and different amounts of admixtures were mixed with the tested soil to explore the effect of the wet environment on the stability and durability of the stabilised gypsum–clay soil. Cylindrical stabilised soil specimens were cured for 3, 7, and 28 days and then soaked in water for different intervals up to 60 days. The soaked samples were evaluated based on the compressive strength, durability index, deformation changes, soil deterioration, and water absorption. The results show that increasing the content of both types of admixtures had a positive effect on the improvement of stability and durability for the tested soil in a wet environment, while the increase in the admixture ratio had a slightly negative effect on both the stability and the durability of the samples subjected to soaking. Short soaking times, up to 15 days, had a negative effect on the stability, durability, and changes in volume, and brought about a deterioration in the soluble soil and the water absorption compared with longer soaking times. The short curing times of 3 and 7 days exhibited a positive effect on the improvement of the stability, strength, and durability for the stabilised specimens subjected to soaking compared with the longer curing time of 28 days. Increasing the admixture content and soaking time had a significant effect on the water absorption and the soil deterioration of the tested soil. The effect of the soaking condition on the volume changes for the soil stabilised with the two admixtures was found to be insignificant, because the maximum volume change was found to be less than 0.15%.     

Heavy metal removal from waste water from wet lime(stone)—gypsum flue gas desulfurization plants

Waste water from wet lime(stone) gypsum flue gas desulfurization processes for coal-fired boilers contains suspended solids (gypsum, silica, hydroxides of iron and aluminum) and soluble salts (chlorides and sulfates of calcium, sodium and magnesium). Furthermore, small amounts of heavy metals such as As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Se and Zn are present in these waste water streams. A treatment method has been developed to remove these heavy metals very efficiently. This method has been based on coprecipitation of metal hydroxides and sulfides. The hydroxide and sulfide precipitates are removed by a coagulation/flocculation technique followed by gravity settling. The coprecipitation can be carried out with sodium hydroxide or with lime. Both cases were investigated in two different pilot plants with synthetically composed waste water and with actual waste water from three different types of wet lime(stone)—gypsum flue gas desulfurization plants (lime—gypsum FGD plants without a prescrubber, one using seawater and another using river water as process water; a limestone—gypsum FGD plant with a prescrubber using river water as process water).     

Stabilization of black cotton soil subgrade using sawdust ash and lime

This research dwells on how black cotton soil (BCS) could be stabilized and made a suitable subgrade material using sawdust, a readily and cheaply available material. Sawdust was burnt to ashes in a furnace at a temperature of 800?°C and then mixed with BCS in varying proportions of 4%, 8%, 12%, 16% and 20%. Since the trial mixes showed that the use of 16% sawdust ash gave better results, the BCS treated with optimum sawdust ash content of 16% was further stabilized with 2%, 4%, 6%, 8%, and 10% lime. Optimum reduction in liquid limit, differential free swell, plasticity index as well as optimum increase in CBR and specific gravity was achieved when BCS treated with 16% sawdust ash was stabilized with 4% lime. Scanning electron microscope images of the freshly prepared stabilized soil showed the occurrence of flocculation and agglomeration while X-ray diffraction tests on the cured stabilized soils showed the occurrence of pozzolanic reactions. It was thus concluded that treating BCS with sawdust burnt in an appropriate environment and combined with lime enhances its strength. It also offers another way to dispose of sawdust.     

Statistical analyses of discontinuity parameters of Gölbaši (Ankara) Andesites,Süpren (Eskišehir) marble,and Porsuk Dam (Eskišehir) peridotite in Turkey

In this study aperture, persistence and spacing of discontinuities measured from three different rock types are treated statistically to determine their frequency distributions. Andesites of Gölba?i-Ankara, the marble of Süpren-Eski?ehir and the peridotite of Porsuk Dam-Eski?ehir are selected as rock types for which scan line surveys have been carried out. Statistical analyses are aimed at evaluating the distribution parameters, histograms, moments around zero, and moments around the mean of each set of data. The parameters are then utilized for making comparisons between the theoretical and the observed frequency distributions by means of Chi-Square tests and the method of Cross Correlations. Results of the statistical analyses have shown that the frequency distributions may not be the same in all rock types. The degree of weathering affects the frequency distribution of discontinuity spacing even in the same rock.     

Renovation of existing office buildings in regard to energy economy: An example from Ankara,Turkey

Unit energy consumption of existing buildings in Turkey is excessive. While average energy consumption of residential buildings in Europe is 100 kWh/m² per year, it is about 200 kWh/m² per year in Turkey. The principle reason for this, is that there was not any regulation on thermal insulation issues until recent years. However, the fiscal value of total energy consumption in residential buildings is about $2.5 billion. Recent research has shown that 40% of this energy consumption could be saved, provided that using energy efficiently. Furthermore, every reduction in energy-usage has a significant influence on environmental protection and CO₂ emissions. This study has focused on energy efficiency in a building of public sector that had been inaugurated in 1988 in Ankara. During the pre-investigative step, it has been determined that 47% of total energy consumption of the building could be saved.     

粉煤灰改良粘土可塑性和抗剪强度的试验研究

利用试验，从化学和物理两方面研究了粉煤灰与土的比和养护时间对改良粘土可塑性和抗剪强度的影响，并分析了其影响机理，从而保证粘土工程使用的安全性。     

The effect of slaked lime,anhydrous gypsum and limestone powder on properties of blast furnace slag cement mortar and concrete

Basic properties of blast furnace slag cement mortar and concrete are investigated by adding inorganic activators. The result of this research concludes that slag cement mixed with suitable activator agents such as lime, gypsum and limestone powder could accelerate the compressive strength and tighten pore structure at early age. The addition of activator into mortar and concrete containing slag cement produces superior properties, reduced shrinkage and less carbonation compared to mortar and concrete containing slag cement without the addition of activator. Consequently, there are possibilities for manufacturing blast furnace slag cement, which could compensate the weak properties at early curing age. When compared with ordinary Portland cement, this cement has superior characteristics for long curing age.     

粉土黏粒含量与塑性指数的相关性分析及应用

通过收集北京南部地区粉土的土工试验资料,利用SPSS统计分析软件,对黏粒含量和其他物理性质指标进行相关性分析,得出黏粒含量与塑性指数的回归方程,并分析了附近场地粉土黏粒含量实测值与回归方程计算值的误差,验证了该回归方程在北京南部地区的实用性。     

关于石灰改良高液限土试验设计的一般研究

以广梧高速公路汉口—双凤第四合同段工程为例,从试验的角度对石灰改良高液限土进行了分析,提出以试验结果为参照,可有效控制工程质量和降低工程成本。     

Stabilization of soft clay using short fibers and poly vinyl alcohol

In this study, the effect of the combined addition of fibers and a nontraditional polymer on the mechanical behavior of a clay was investigated. Poly vinyl alcohol, PVA, used as a solution with concentrations of 0.1%, 0.3%, 0.5%, 1.0% and 1.5% and 1,2,3,4 Butane Tetra Carboxylic Acid, BTCA was added as a crosslinking agent at concentration rates of 0.1%, 0.3% and 0.5%, respectively. Short polypropylene fibers were added to the clay at proportionate quantities of 0.25% and 0.50% of the dry weight of the soil. Clay samples were prepared for unconfined compressive strength (UCS) tests at two different initial void ratio values, denoting relatively stiff and markedly soft states. UCS tests were conducted on both 1-day and 14-day cured samples. The results confirmed significant UCS improvements with combined fiber reinforcement and PVA-BTCA stabilization when samples were cured for 14 days. It was also observed that fiber reinforcement outperformed PVA-BTCA stabilization for clays with the lower initial void ratio. PVA-BTCA stabilization was however found to be superior to fiber reinforcement in clays with a relatively higher initial void ratio. The effect of fiber reinforcement and PVA-BTCA stabilization on the stability of soils subjected to excessive wetting was also evaluated using soaking tests. Stabilization with PVA and BTCA was found to enhance the stability of soaked samples significantly. The results of soaking tests proved that BTCA made PVA-stabilized samples more durable when exposed to soaking.