This paper discusses the influence of adding various amounts of cement to and changing the water content of clayey soil and their effects on controlling the settlement of a superstructure with various improvement area ratios (IARs). As a first step, the physical and mechanical properties of clayey soil from Bandar Imam Port, Iran, with 4, 6, 8 and 10% cement content and various water contents (30, 48 and 70%) were determined. Sample preparation was carried out using the wet deep soil mixing (DSM) method. The relationship between secant modulus at 50% strength (E50) and curing time for various cement contents was determined. In addition, different DSM column patterns with IARs of 0, 0·2, 0·3, 0·4 and 0·5, considering floating and end bearing DSM columns, were modelled using the finite-element method. Soil improvement by mass mixing of layers 2–7 m thick was also studied. The optimisation of various IARs and DSM characteristics and patterns enables production of a chart guide for preliminary design.
This study investigates the effects of Nano-silica and Nano-alumina on the Marl soil as a problematic soil in Tabriz, Iran. These soils, which are among the swellable soils, constitute the foundation of most projects in Tabriz. Due to water absorption, these soils are liable to volume change and instability risks in the foundation of projects. Consequently, various physical and chemical methods have been employed to stabilize these soils. In the present study, for the first time, the reconstructed samples of Tabriz Marl were stabilized with various percentages of Nano-silica and Nano-alumina, which have fewer environmental effects in comparison with ordinary additives such as Portland cement or lime. In addition, soil swelling behaviors have been evaluated by various experiments including Atterberg limits, density, free swelling, swelling pressure, California Bearing Ratio (CBR) tests, direct shear tests, Field Emission Scanning Electron Microscopy (FESEM), and X-ray powder diffraction (XRD) analyses which were conducted at 1, 7, and 28 days of curing times. The results show that Nano-alumina has a greater effect on reducing the swelling of stabilized samples than Nano-silica. However, the effect of Nano-silica has been more than Nano-alumina on increasing the strength CBR.
The current research was implemented to monitor and rehabilitate the structural health of Masjed-E-Soleyman, M.E.S., dam with 177 m height, one of the highest Iranian rockfill dams. This dam suffers from extensive and unpredictable settlements and related cracks. In order to investigate the nonhomogeneous (Conglomerate) rockfill's brittle behavior in Before-After and During the triaxial tests, a series of laboratory tests in conventional stress paths were carried out using a large-scale triaxial apparatus. A numerical time-dependent model was introduced inside the laboratory tests to find a relationship between particle breakage and the time-dependent settlement of the embankment dam. The core of this paper aimed to investigate the particle breakage of Conglomerate material in the M.E.S. dam and to modify the nonhomogeneous relative particle breakage index, by establishing a relationship between relative particle breakage index for this material and the plastic work. The conclusions of this research were categorized into three significant steps. The Breakage Index (Before-After tests) was calculated in the first step. Secondly, a relationship between Breakage Index and plastic work (During tests) was introduced. Finally, a predictable pattern of dam's crest settlement was presented using numerical Viscoelastic Burgers model and its calibration with accurate monitoring data of the M.E.S. dam.
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