Ibrahim Naeimifar, Shahaboddin Yasrobi, Ali Uromeie, Hatef Hashemi,
Volume 10, Issue 4 (Vol. 10, No. 4 Winter 2017 2017)
Abstract
Evaluation of the excavation-induced ground movements is an important design aspect of supporting system in urban areas. This evaluation process is more critical to the old buildings or sensitive structures which exist in the excavation-affected zone. Frame distortion and crack generation are predictor, of building damage resulted from excavation-induced ground movements, which pose challenges to projects involving deep excavations. Geological and geotechnical conditions of excavation area have significant effects on excavation-induced ground movements and the related damages. In some cases, excavation area may be located in the jointed or weathered rocks. Under such conditions, the geological properties of supported ground become more noticeable due to the discontinuities and anisotropic effects. This paper is aimed to study the performance of excavation walls supported by nails in jointed rocks medium. The performance of nailed wall is investigated based on evaluating the excavation-induced ground movements and damage levels of structures in the excavation-affected zone. For this purpose, a set of calibrated 2D finite element models are developed by taking into account the nail-rock-structure interactions, the anisotropic properties of jointed rock, and the staged construction process using ABAQUS software. The results highlight the effects of different parameters such as joint inclinations, anisotropy of rocks and nail inclinations on deformation parameters of excavation wall supported by nails, and induced damage in the structures adjacent to the excavation area. The results also show the relationship between excavation-induced deformation and the level of damage in the adjacent structure.
Omid Naeemifar, S.shahab Yasrobi,
Volume 12, Issue 2 (Vol. 12, No. 2, Summer 2018 2018)
Abstract
of initial texture and plastic fine content has been investigated. In order to model the different deposition condition four different specimen preparation methods are used. The tests are conducted on sands and its combination with to 25 fine percent using static and cyclic method. Four different specimen preparation methods are used consisting of Dry Funnel Deposition (DFD), Water Sedimentation (WS), Moist Tamping (MT) and Air Pluviation (AP). Each method may be useful to model the behavior of some special deposited soils. For example, DFD is the best method to model the natural deposition of silty sands, while the WS method is suitable for simulating the sands natural deposition in the rivers. MT method is the best method to simulate the behavior of compacted embankments while SD method is suitable to prevent the segregation of particles with respect to other methods like Water Pluviation. Effect of sample preparation methods on the sands and silty sands behavior is investigated to some extent, while the clayey sands are rarely considered. The results show that water sedimentation method, Air pluviation method and Dry funnel deposition method tends to create dilative textures with continuous dilative behavior even in high clay fine content. In contrast, the wet tamping method shows the dilative behavior only for clean sands specimens and increasing fines will results in instability and complete strain softening behavior. In cyclic loading the difference between different methods are less with respect to static loading. It seems that the results of different methods tends to be identical with increasing in fine content. In general, increasing fine content up to 20 percent results in more instability. After that a threshold value can be estimated bout 2 percent, after that the instability becomes less with continuous increase in fines content. The valuable result is that the threshold value is not dependent on the specimen preparation method or initial texture of specimens.
