Ayhan Gurbuz

SCALE EFFECTS IN LATERAL LOAD RESPONSE OF LARGE DIAMETER MONOPILES

Monopile foundations are frequently used for offshore wind energy converters. These piles are highly laterally loaded structures with large horizontal forces and bending moments. Due to the harsh environmental conditions in the southern North Sea diameters of 4 to 8 m are required to maintain serviceability. In common practice smaller laterally loaded pipe piles are designed using the well-known p-y-method, in which the pile-soil stiffness is considered by nonlinear p-y-curves derived from field tests. An alternative design method is the strain wedge method in which the pile response is derived from the stress-strain relationship of the soil assuming a certain failure zone ahead of the pile. In the present paper, the design of a large diameter monopile foundation for typical loading conditions is presented. The pile response in cohesionless soil determined by the p-y method and the strain wedge method is compared with a finite element (FE) analysis with respect to scale effects when extrapolated from commonly used pipe pile diameters to large size monopiles.

Marble powder to stabilise clayey soils in sub-bases for road construction

Marble, used extensively as construction materials, yields huge amount of marble powder waste from natural marble stone processing. Therefore, it is essential to utilise marble powder waste in order to eliminate its negative effect on environment and to obtain economic benefit from it. There are almost no studies in the literature concerning the use of marble waste in the stabilisation of clayey soil under freeze–thaw effects. In this study, a pioneer attempt is made to evaluate the effectiveness of using marble powder in the stabilisation of clayey soil in a road construction under freeze–thaw effects. Natural clay is mixed with marble powder at different percentages; then, strength in terms of the results of unconfined compressive tests and durability in terms of mass loss after freeze–thaw cycles are investigated. As the marble powder content in this study reaches 10% in the clayey soil, the unconfined compressive strength of specimens rises to a peak point; meanwhile, plasticity of mixtures decreases. Mass loss as criteria for durability behaviour in the marble powder-stabilised soils at the end of freeze–thaw cycles is almost 5%. Test results indicate that marble powder could be used as a stabilisation material for clayey-type soils in sub-bases in highway construction under freeze–thaw effect.

Bacteria-Induced Cementation in Sandy Soils

Bacteria-induced calcite precipitation (BICP) is a promising technique that utilizes bacteria to form calcite precipitates throughout the soil matrix, leading to an increase in soil strength and stiffness. This research investigated BICP in two types of sands under sterile and nonsterile conditions. Bacteria formation and BICP in the sterilized sand specimens are higher than those in the nonsterilized sand specimens. The development of calcite with time is initially greater for the sand specimens containing calcite. Scanning electron microscope imaging allowed the detection of cementation from calcite precipitation on the surface and pores of the sand matrix. The effects of injecting nutrient mediums and bacteria into the specimens, as well as pH of soil samples on BICP were investigated. The bearing capacity of biologically treated vs. untreated sand specimens were determined especially by laboratory foundation loading tests.

Monitored Performance of a Concrete-Faced Sand-Gravel Dam

AbstractConcrete-faced rockfill dams (CFRDs) can be configured as concrete-faced sand-gravel dams (CFSGDs) during design and planning stages based on geological conditions and available rockfill materials at the construction site. Karacasu Dam, located in Turkey, is a pioneering example of a CFSGD and is built primarily on marl. The primary purpose of this study is to examine the monitored performance of the Karacasu Dam by using data collected from 18 earth pressure cells and 30 displacement cells embedded within the dam body, as well as 15 joint meters installed on its concrete face. This quantitative examination provides various crucial insights for building dams of this type in the future.

Evaluation of Boron Ore in Cement Production

A new genre of high belite cement named boron-modified active belite (BAB) cement that was developed using byproduct of boric acid production was investigated. The cement proved superior in compressive strength and permeability characteristics in the previous studies. Long term storage of cement is known to alter the mechanical properties of concrete made with the aged cement. The article investigated the BAB cement in aged condition—stored in silos for about three years—variations of mechanical and physical properties of specimens during a one-year period. An additional comparison is also performed with specimens cast using fresh Ordinary Portland Cement (OPC) of the same grade in order to present the development of mechanical and physical properties in a qualitative manner. Lower 28 day compressive strength values are observed for BAB cement compared to OPC specimens; however, higher rate of strength development of BAB cement resulting from high belite content led to comparable long term strength values with OPC specimens.

The Lateral Response of Single Free Headed Piles in Sandy Soils - Methods, Measurements and Reliability

Piles require withstanding lateral loads from various sources such as wind, waves, traffic, earthquake, soil and water. While the Strength Limit State controls the design of axially loaded piles, serviceability often controls the design of laterally loaded piles, i.e. the applied load is controlled by the magnitude of the limiting lateral displacement. The analysis of laterally loaded piles is complicated due to the pile-soil interaction, where the lateral soil resistance developed along the pile is a function of the pile’s deflection being a function of the soil’s resistance. Laterally loaded piles are commonly designed using computer-based analysis methods solving the differential equation of a beam on elastic foundation that controls the load-deflection relations, utilizing what is known as p-y curves for the local spring factor-load-deflection relations. Software packages; LPile 5 Plus in which the p-y curves are constituted based on past pile load tests and soil testing results, and the Strain Wedge Model (SWM) in which the p-y curves are derived from the assumption of a wedge failure zone ahead of the pile, were used in this study. Both analyses were employed in a parametric study, calculating the piles’ top lateral forces required to obtain given lateral displacements ranging from 0.5 in to 3 in (12.7 to 75.6 mm) in 0.5 in intervals. The results for the two methods are compared and examined against a database of laterally load tested piles. Factors affecting the performance of the analyses are discussed.

Prediction and Reliability of Pipe Piles Response to Lateral Loading

Load-deflection relations of piles subjected to lateral loading are routinely required for design. The use of large diameter open pipe piles became common since its application as foundations for offshore structures, and more recently for bridge retrofitting and new construction designed for withstanding earthquake loading. The accuracy and reliability of the analysis methods remains usually unknown as it requires the systematic examination of the measured performance of many piles. As part of a research aimed at developing the serviceability limit states for the AASHTO specifications, an evaluation of the methods predicting the response of piles to lateral loads was required. This paper presents a database of laterally loaded open and closed pipe piles which were examined by various analysis methods. The performance of the methods when applied to open pipe piles and all pipe piles is reported along with practical conclusions for their use.

Modulus of subgrade reaction that varies with magnitude of displacement of cohesionless soil

Modulus of subgrade reaction is one of the required design parameters in any structural analyses of shallow foundations. However, the constant values of modulus of subgrade reaction that are determined from either from literature studies or the results of plate load tests, regardless of magnitude of soil’s displacement under design loads, have been used in structural designs of foundations. In this study, the results of 43 published full-scale field plate load tests in cohesionles soils were gathered to expose any variation in the values of modulus of subgrade reaction as soil’s displacement increases. Extensive finite element (FE) analyses were carried out while the results of FE analyses were compared with actual measured results of field load tests. The results of analyses indicated that both the modulus of subgrade reaction decrease with increase in magnitude of displacement of soils and internal forces of a design of structural frame is higher with the values of modulus of subgrade reaction that are sensitive to soil’s displacement are implemented into analyses. Therefore, structural dimensions of any structure with the constant values of modulus of subgrade reaction would not be a precise engineering solution.

The application of distributed fibre sensors in determination of seepage in Derince Dam

Monitoring of civil infrastructure systems has emerged as a powerful tool for condition assessment of infrastructure performance. Structures could be monitored periodically from a central station located several kilometres away from the field with help of widespread use of modern telecommunication technologies. Fibre sensing technology is increasingly used in civil engineering applications. Distributed fibre optic sensing offers the ability to measure temperatures, strain, leakage, etc., at thousands of points along a single fibre. A case of seepage along plinth of concrete faced Derince Dam, located in Turkey, is measured continuously and presented in this paper while an application of distributed fibre sensor technology is used. The case helps to disclose potential leakage along the plinth in order to minimise any risk.

New Simple Approach to Prediction of Axial Settlement of Single Piles under Design Load

AbstractPiles have been used to transfer superstructure (bridges, buildings, etc.) loads to deeper competent bearing strata to minimize settlements. Accurate predictions of design settlements of vertically loaded piles under working load are a critical issue in the design of pile foundations. Numerous comprehensive trials, built on a regression-based predictive formula that produces the axial settlement using elastic shortening as the input variable, were performed in this study, and a simple relationship was established between the elastic shortening of piles and the measured design settlements of 93 full-scale pile load tests installed in variable bearing materials. The calculated axial settlements of piles from the proposed method in this study were compared to the measured axial settlements of the piles. Accuracy and validity of the proposed method were verified through conventional statistical analysis in terms of mean of bias (λm) and coefficient of variation (μ). The proposed method yielded values ...