Estimation of the compression behaviour of reconstituted clays
Abstract The void index is a relative quantity measuring the position of the current void ratio of a clay against the void ratios of the clay at two specific vertical effective stresses (i.e., σv′ = 100 kPa and σv′ = 1000 kPa). Based on this concept, a simple systematic tool is proposed for estimating the compression behaviour of reconstituted clays over a wide range of stresses and water contents. Following the practice of geotechnical engineering computation, the compression behaviour of clays is idealised as linear segments in the Iv ~ lnp′ (or the void index and the mean effective stress) space. Considering the variation in the available data, there are three related but independent models for describing the compression behaviour of reconstituted clays. The accuracy of estimation increases with the level of available data. The proposed estimation is used to simulate the behaviour of a variety of reconstituted clays over a wide range of stresses and water contents. With different levels of available data, the estimation is evaluated on the basis of these simulations. The proposed estimation can take maximum use of available data and provide a simple yet practical tool for calculating the compression behaviour of reconstituted clays and a basic parameter for geotechnical engineering computations, the compression index. An empirical equation for the initial compression index is also suggested and verified.
Experimental study of primary consolidation time for structured and destructured clays
Abstract Incremental load one-dimensional consolidation tests were performed on undisturbed and reconstituted specimens of seven natural clays with a predominant clay mineral of illite. Both the settlement and the base pore pressure under step load increments were measured during the dissipation of pore pressure. The change law in the primary consolidation time determined by the pore pressure dissipation with increasing stress level is found to be contrary to that determined by the Taylor method and the Casagrande method which are often used in laboratory tests and engineering practice. The primary consolidation time determined based on the time-dependent settlement observations is smaller than that determined by the pore pressure dissipation for the natural clays investigated. Pore pressure is generally not completely dissipated at the primary consolidation time determined by the Taylor method and the Casagrande method. Such remaining pore pressure may reach a quite high percentage of the step load increment for the investigated specimens. The settlement determined by the Taylor method and the Casagrande method may be significantly underestimated due to the dissipation of remaining pore pressure. Attention should be paid to the possible distortion on consolidation behavior in laboratory tests and engineering practice due to the remaining pore pressure and the associated settlement.
Development of Science and Technology in the Iranian Electric Power Industry: Challenges and Future Progress
This chapter examines four key segments of the electric power industry in Iran: generation, transportation, distribution and consumption. It reviews the method, development, and evolution of electric power generation in the country. Specifically, the chapter reviews the structure of the electric industry, the main players, institutions, standards as well as laws, human resources, technology, the export and import markets, and engineering management of the industry in the country. Finally, the challenges facing the industry will be identified and policy suggestions to remedy the problems will be provided.