This study discusses the results of numerical modeling aspect of aggregate pier foundations (aggregate piers) in soft, compressible soils. FLAC 2D (Fast Lagrangian Analysis of Continua), a finite difference code is utilized in the analyses. Use of axisymmetry enabled to visualize a three dimensional model throughout this research. The primary objective of this research is to make comparisons for stress concentration ratio &lsquo / n&rsquo / , and settlement reduction ratio b for given variables consisting of length, diameter, elastic modulus of the aggregate piers, and foundation pressures. Analyses have been carried out with 1, 1.5, 2, and 3 m long piers with diameters of 60 cm, and 80 cm, placed under a circular footing in 1.30 m diameter. Two values for elastic modulus of the piers have been used to reflect the effect of pier stiffness on settlement behavior. Analysis and design methodology have been carried out in three stages. The first stage consists of modeling the matrix soil with an elastic constitutive model and exerting foundation pressures to first check the accuracy of the mesh by comparing the effective vertical stress and settlement values by analytical methods. Once satisfactory results are achieved, modeling of a rigid foundation is carried out. Consequently, aggregate piers are modeled and loaded. For foundation pressures, a range of values consisting of 25, 50, 75, and 100 kPa have been chosen to see the behavior of piers under variable foundation pressures. There are solid outcomes of this study. It concludes by stating that the settlement behavior of piers having L/d ratios greater than 3.75, are alike. Thus, there is almost no additional settlement improvement achieved with piers longer than 3 m with 60 cm pier diameter.

This study aims to determine the safe and sustainable development and management of groundwater resources in Ergene River Basin located in northwestern Turkey. A numerical groundwater model was developed for the Sandy Complex aquifer, which is the most productive and the most widespread aquifer in the basin. The finite difference model with 5900 cells was used to represent the steady and unsteady flow in the aquifer. The model was calibrated in two steps: a steady state calibration by using the observed groundwater levels of January 1970, followed by a transient calibration by using the observed groundwater levels for the period of January 1970 and December 2000. The resulting model was used to develop groundwater pumping scenarios in order to predict the changes in the aquifer system under a set of different pumpage conditions for a planning period of 30 years between January 2001 and December 2030. A total of eight pumping scenarios were developed under transient flow conditions for the planning period and the results were evaluated to determine the safe and sustainable yields of the aquifer. The results, presented in the form of a trade-off curve, demonstrate that the continuation of the present pumping rates exceeds both the safe and the sustainable yields of the aquifer system.

Vertical and inclined soil nails under footings as settlement &ndash / reducing elements is investigated using a physical 1g model in the laboratory. Nails are not connected to footing, they are not so long and vertical settlement of nails is very large compared to usual limits encountered for piles or micropiles. Following the settlement of footing, they share the load together with the footing. The skin friction is mostly mobilized and end-bearing failure occurs continuously during the settlement. The system of footing- soil nail is studied by model square footings of 30 mm x 30 mm and 50 mm x 50 mm breadth dimensions and remoulded kaolin clay consolidated under constant controlled stress of 50 kPa in 200 mm cube boxes. In the first section of the testing series 4, 5, 9 and 12 nails were inserted into soil in 3B, 2.4B, 1.33B and B lengths, respectively. In the second section, 4 and 6 nails in 1.5B and 2B lengths were tested for vertical and 15 degrees and 30 degrees inclined cases. Settlements of footings were measured under constant footing pressure for all groups. Several tests were repeated in each group of testing series. It is concluded that keeping the total nail length constant, decreasing the nail number thus using longer individual nails is more effective in decreasing the footing settlements. 15 degrees inclined nails decrease total settlements more.

The purpose of this study is to assess the engineering geological and geotechnical characteristics and to perform seismic hazard studies of the Upper Pliocene and Quaternary deposits located towards the west of Ankara. Based on a general engineering geological and seismic characterization of the site, site classification systems are assigned for seismic hazard assessment studies. The objective of the research is to determine the regional and local seismic soil conditions, predominant periods and ground amplifications, and to idealize the soil profile of the sites by the aid of surface geophysical methods. These studies are combined and integrated with the geotechnical database from a variety of in-situ and laboratory studies that are compiled from present and previous studies regarding the project area and then transferred to an analytical environment for creating relevant information for our site. Then, engineering geological and geotechnical seismic characterization along with seismic zoning map preperation is accomplished. Finally, based on a general engineering geological and geotechnical site characterization, site classification systems are assigned to account for site effects in seismic hazard assessments along with the assessment of mitigation and remediation of seismic hazards.

Thesis (M. Sc. (Urb. Plan.))--University of Hong Kong, 1994. / Includes bibliographical references.

ABSTRACT 3-D SOIL STRUCTURE INTERACTION ANALYSES OF THREE IDENTICAL BUILDINGS IN SAKARYA CITY AFTER 17 AUGUST 1999 KOCAELI EARTHQUAKE &Uuml / nal,Orhan M.S., Department of Civil Engineering, Supervisor: Assist. Prof. Dr Kemal &Ouml / nder &Ccedil / etin October 2003, 116 Pages The aim of this study is to analyze the soil structure interaction of three identical buildings on &ordf / ahinler Street of Sakarya city which had no damage to heavy damage after the Kocaeli (1999) earthquake. For the purpose of 3-D dynamic nonlinear analysis of the soil site and the overlying structures, Flac3D software was chosen as the numerical modeling framework. Soil properties were determined by using the results of available site investigation studies. A three dimensional mesh was created to represent the topographic and geometric constraints of the problem. Linearly elastic perfectly plastic constitutive model was implemented to model the soil behavior. The results of 3-D dynamic numerical analyses in the forms of acceleration, displacement, strain, stress and pore pressure were presented. The higher acceleration, strain and stress levels calculated under the collapsed building can be attributed as the major cause of poor performance of the structure.

The goal of this study is to develop probabilistically based empirical correlations for seismic performance assessment of buried pipelines. Within the scope of these research efforts, pipeline performance case histories have been compiled from Duzce city after Duzce earthquake. The characteristics of Duzce water supply and distribution system with the earthquake damage on the system were studied. Correlations of the damage patterns with the water distribution system, earthquake and geotechnical characteristics have been developed. Moreover spatial distributions of the earthquake effects havebeen transferred into Geographic Information System (GIS) format. As a result of these studies, it was intended to define the seismic, geotechnical and structural parameters which may explain the spatial variability of the observed seismic pipeline hazard. For the development of such correlations, a maximum likelihood framework for the probabilistic assessment of seismically induced buried pipeline performance is described. A database, consisting of postearthquake field observations of buried pipeline performance after Duzce earthquake in conjunction with in-situ index test results, is used for the development of probabilistically based seismic pipeline performance correlations. As a result of careful processing of available data, the variables of the problem are selected as: liquefaction susceptibility of soil, thickness of soft soil layer if it exists, peak ground acceleration and estimated ground deformations. A limit state function is defined in terms of these variables. Repairs on the pipeline system due to earthquake are compiled with the surrounding soil and earthquake parameters and the correlations of pipeline performances with the mentioned variables are determined. Different sets of fragility curves are developed for seismic pipeline performance problem, representing various sources of uncertainty that are intrinsic to the problem. Such information is believed to be useful to utility system operators in planning a seismic retrofit or upgrade program for existing pipeline systems.

In this thesis, permeability impairment caused by drilling fluids and subsequent cleaning and permeability enhancement by back-flow were investigated by means of experimental and simulation studies. Permeability damage caused by three different drilling fluids was measured experimentally by core tests as a function of the filtration pressure and analyzed using a simulator describing the fines migration and retention in porous media. The pore throat plugging criteria for the three drilling fluids were determined. The particle concentration and the fraction of depositing particles were obtained simultaneously as a function of time and distance along the core length by numerical solution. Simulations were run both with experimental data in forward and backward directions along the core samples. Permeability damage ratio was correlated with respect to drilling filtration pressure specially for each type of the drilling fluids and type curves were constructed. Simulation results accurately match the experimental data, indicating that this simulator can be used for the estimation of permeability reduction, and the permeability and porosity variation along the core samples at various filtration pressures. X-Ray digital image subtraction was applied to different sections of the core plugs before and after the circulation to visualize the fines migration into porous media. The maximum damage ratio was obtained with the CMC added drilling fluid with 81 %. In the absence of CMC and Polymer-XT, the damage ratio was found as 72.8%. It was also determined that a polymer-added drilling fluid characterized with 63.8% permeability damage ratio is the optimum drilling fluid, causing less formation damage than the water-based bentonite mud.

The effects of basin edge slope on the dynamic response of soil deposits are assessed by using one-dimensional and two-dimensional numerical analyses. 24 basin models having trapezoidal cross section are generated to represent different geometries (basin depth, basin edge slope) and soil type. Harmonic base motions with different predominant periods (Tp) are used in the analyses. The results indicate that, for a constant basin edge slope and a constant ratio of fundamental period of site to the predominant period of base motion (Tn/Tp), the response is almost the same for different soil types, basin depths and base motions. In the sloping edge region, one-dimensional response analysis predictions are found to be conservative compared to two-dimensional analysis predictions / however beyond this region they are unconservatively biased by a factor as high as 1.5. The sloping edge region and the horizontal region of the basin are denoted by normalized distance (ND) values varying from 0 to 1 and 1 to 2 respectively. The critical region where maximum amplification observed falls in the range of ND=1.0 to ND=1.5 for basins having slopes greater than 30o. The lower boundary of the critical region is shifted towards as low as ND=0.2 for basins having slopes less than 30o. For a constant value of Tn/Tp, the increase in the amplification is smooth for basins with gentle slopes as compared to basins with steep slopes for the region where ND~1. For a basin and earthquake couple approaching to resonance state (Tn/Tp=1), the amplification for the region where ND is greater than 1 is found to be as high as 100% of that is found for the region where ND~1.

Among the hard-hit cities during 17 August 1999 Kocaeli Earthquake (Mw 7.4), Adapazari is known for the prominent role of site conditions in damage distribution. Since the strong ground motion during the event was recorded only on a rock site, it is necessary to estimate the response of alluvium basin before any study on the relationship between the damage and the parameters of ground motion. Therefore, a series of site and laboratory tests were done on Adapazari soils in order to decrease the uncertainty in estimation of their dynamic properties. In downtown Adapazari, a 118 m deep borehole was opened in the vicinity of heavily damaged buildings for sample recovery and in-situ testing. The stiffness of the soils in-situ is first investigated by standard penetration tests (SPT) and by velocity measurements with P-S suspension logging technique. Disturbed samples were recovered by core-barrel and split-barrel samplers. 18 Thin-Walled tubes were successively used for recovering undisturbed samples. A series of monotonic and cyclic direct simple shear tests were done on specimens recovered from the Thin-Walled tubes. It is concluded that the secant shear modulus and damping ratio of soils exposed to severe shaking during the 1999 event are significantly smaller than those estimated by using the empirical relationships in literature. It is also observed that the reversed-S shaped hysteresis loops are typical for cyclic response of the samples.