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.
Time-dependent compression behaviour of dredged clays at high water contents in China
Abstract Incremental load one-dimensional consolidation tests were performed on dredged clays with and without ageing to investigate their time-dependent compression behaviour. The dredged clays investigated had a wide spectrum of liquid limits within 55.6% to 100% and a predominant clay mineral of illite. It is found that vertical yield stresses develop notably during ageing. The developed vertical yield stresses vary within the range of 1.2 to 1.8 times the specifically assigned vertical effective stress under which ageing is allowed for 15 to 105 days. But the corresponding ageing volumetric strains are small, varying within the range of 0.6% to 3.4% with most being less than 2%. The test results obtained also allow proposing an empirical equation of assessing vertical yield stress. The changing law of vertical yield stress with stress level for ageing, ageing time, soil properties is investigated based on the empirical equation. Moreover, it is found that the structural resistance of dredged clays developed during ageing for a period of consolidation time up to 105 days is weak compared with the sedimentation compression line of natural clays developed during long geological ageing. But the compression curves of dredged clays with ageing converge slowly to the intrinsic compression line over a wide range of stresses, like natural clays subjected to the effect of soil structure developed during long depositional and post-depositional processes.
The Inca Occupation of the South Coast of Peru
like the others, however; it forks into several nearly parallel ravines of which the largest are Huayuri, Rio Grande-Palpa, Ingenio (called Collao in ancient times), Nasca proper (the ancient Caxamarca), Taruga, and Poroma. Due to peculiarities of the local topography, the irrigated areas in Ica and the ravines of Nasca are located inland, at the foot of the mountains, rather than at the mouths of the rivers as is more usual in Peruvian coastal valleys. No sharp natural or cultural boundary separates the valley of Chincha from the valleys of Cafiete (ancient Huarco and Runahuana), Asia, and Mala, the next valleys going up the coast to the northwest. At the other end of the area we are considering, however, there is a sharp break; beyond Yauca the Andean foothills reach out to the sea, natural conditions are quite different, and there are important differences in the archaeological picture as well. The historical sources which mention the south coast are not particularly helpful, except in so far as they provide us with a few dates. To begin with, no chronicler gives an explicit account of the political organization of the south coast at the time it came into contact with the Incas. It can, perhaps, be inferred from Cabello Balboa's statements about common policy toward the Inca invaders that there was some sort of political connection between the valleys of Mala, Cafiete, and Chincha, but the connection need have been no more than a temporary military alliance. Cabello makes no mention at all of Pisco. The valleys of Ica, Nasca, and 125