Mehmet Murat Monkul

Short note: A Visual Basic program for analyzing oedometer test results and evaluating intergranular void ratio

A visual basic program (POCI) is proposed and explained in order to analyze oedometer test results. Oedometer test results have vital importance from geotechnical point of view, since settlement requirements usually control the design of foundations. The software POCI is developed in order perform the necessary calculations for convential oedometer test. The change of global void ratio and stress-strain characteristics can be observed both numerically and graphically. It enables the users to calculate some parameters such as coefficient of consolidation, compression index, recompression index, and preconsolidation pressure depending on the type and stress history of the soil. Moreover, it adopts the concept of intergranular void ratio which may be important especially in the compression behavior of sandy soils. POCI shows the variation of intergranular void ratio and also enables the users to calculate granular compression index.

On Some of the Factors Influencing the Fines' Role on Liquefaction of Silty Sands

Silty sands are among the soil types that are prone to liquefaction when subjected to static or dynamic undrained loading. Today, it is widely accepted that clean sands and silty sands react differently in terms of liquefaction behavior. With this observation, factors influencing fines’ role on such a difference have been investigated by various researchers. Some of those factors such as laboratory specimen preparation method and confining stress are relatively well understood. However, some others such as fines content (FC) are still debated and being investigated. More explicitly, there is not a widely accepted consensus on whether increasing fines content increases or decreases the liquefaction resistance of silty sands, even with the same comparison basis (i.e. loosest possible density after deposition, same void ratio, same relative density etc.). Recently, relative size of silt grains to the sand grains is also found to be another factor influencing the fines’ role on liquefaction behavior of silty sands. In this paper, some of the research in literature regarding liquefaction of silty sands is re-visited and various factors influencing the fines’ role on liquefaction behavior are summarized.

Importance of geotechnical engineering on development and sustainability of lunar bases

Previous volumes of RAST (Recent Advances in Space Technologies) Proceedings presented important developments in various science and engineering disciplines combined in different aspects of space research. However, the very same proceedings have also revealed that the amount of research in some of the fundamental engineering disciplines such as civil engineering is quite limited. Ironically, many countries are planning to construct permanent lunar bases in future. Some of them such as United States and Japan declared this strategy explicitly, whereas some others such as Turkey have it implicitly in their space programs. This paper is written to emphasize the importance of geotechnical engineering, which is one of the several majors of civil engineering, on the development of lunar basis and lunar exploration. Shear strength of soils is briefly overviewed and strength characteristics of various lunar soil simulants are summarized, as shear strength is a key factor for most of the geotechnical analysis. Finally, the importance of simulant gradation on strength characteristics and the need for further research is mentioned with considerations of recent research on terrestrial silty sands.

The Coupled Influence of Relative Density, CSR, Plasticity and Content of Fines on Cyclic Liquefaction Resistance of Sands

ABSTRACT In this study, stress-controlled cyclic simple shear tests were performed on sand specimens with up to 10% silt or clay contents, and coupled effects of plasticity, fines content (FC), relative density (DR) and CSR (cyclic stress ratio) were investigated. The results demonstrated that for sands with low fines content, reasonable trends were obtained when the packing index control parameter was selected as DR. Also, clean sand specimens demonstrated highest liquefaction strength compared with that of sands with fines up to 10% FC. The effect of fines’ plasticity became apparent as the FC increases and CSR reduces in relatively denser specimens.

Validation of Practice Oriented Models and Influence of Soil Stiffness on Lateral Pile Response Due to Kinematic Loading

Earthquakes usually cause both inertial and kinematic loading of pile foundations. Inertial loading and lateral pile response can be predicted to a certain extent by lateral pile load tests for important engineering projects. However, there is no accepted in situ assessment method for pile behavior due to kinematic loading. Therefore, it is important for geotechnical engineering practice to validate the practice oriented models and examine the influence of soil strength parameters on the performance of kinematically loaded piles due to lateral spreading. For this purpose, a well-documented case of full-scale lateral spreading test conducted at Port of Tokachi in Japan by Ashford et al. (2006) is selected as a primary reference in terms of test data and site conditions. Four p-y analyses are performed using a special purpose software based on finite difference technique. The first two investigate the employment of different p-y curves suggested in the literature. The third one investigates the influence of variations in internal friction angle and undrained shear strength. In the fourth analysis, liquefied shear strength and residual shear strength approaches are utilized for the liquefiable layers and their effects are investigated. In all analyses, mobilized lateral pressures in non-liquefied layers are also scrutinized. The results of the analyses are discussed and compared with the measured values in the field. Finally, conclusions are given based on the analyses and discussions.