امیر مهدی حلبیان

Underground box culverts have been applied to facilitate people's living standard in various ways including municipal sewer lines, water mains, gas and oil lines, electric and telecommunication conduits, and pedestrian and subway tunnels. Design and construction of these conduits demand determining exerted pressure due to the soil and embankment weight above. Several ways have been developed for buried culverts and calculating the soil earth to which the buried culvert is subjected to. Accordingly, the applied load is large and culverts are installed under high embankment; applied pressure becomes more significant. Therefore, the reduction and control of the earth load on culverts is of importance. To date, various methods and theories have been proposed to reduce the applied earth load on these underground structures. Among these, two methods are commonly used: Trench Installation (TI) and Induced Trench Installation (ITI). For the TI method, where the culvert is placed in a narrow trench, the deformable soil tends to settle down, while the adjacent trench walls hold the soil in place due to shearing stresses along the interfaces. This leads to the transfer of load from the fill to the trench walls developing soil arching, hence reducing the vertical pressure transfer to buried box culvert. Another method, ITI, is a construction technique employed to reduce the vertical pressure on buried structure, in which a layer of compressible material is placed directly on the buried culvert to induce positive arching thus reducing the applied vertical pressure on culvert crown. Meanwhile, researchers have addressed some deficiencies in each method. Trench Installation in comparison with Induced trench Installation transfers larger earth load to culvert roof. In addition, the development of positive arching directly above the culvert roof transfers more vertical stresses to adjacent soil columns, leading to larger horizontal stresses applied to buried culvert walls. In this study, by taking benefits of these two common methods, an installation method has been proposed in which the culvert is installed in a trench with a layer of deformable material placed above the box culvert roof, called Trenched Induced Trench Installation (TITI). Firstly, the pressure transferred to the culvert under the weight of soil and surface pressure has been validated using numerical analyses compared with analytical equations that predict the applied pressure. Then, two-dimensional finite element analyses have been performed to explore the effect of various factors on the applied pressure on the roof, sidewalls, and bottom of buried box culvert in TITI method. Results show that soil arching reduces the earth pressure on roof and arching developed between box sidewalls and trench walls; the pressure applied on the culvert side walls can be controlled.

Concrete-faced rockll dams (CFRDs) have been widely used for multi-purposes over the world. The construction of CFRD involves placing the rockll in nite thickness layers as a dam body material, and compacting them to reach desired height. A reinforced concrete slab is then constructed at the upstream face of the dam. The concrete face will transfer the water pressure imposed by reservoir to the rockll and nally to the dam foundation. During impounding of CFRDs reservoir, the upstream concrete face undergoes deformations, resulting in the development of compressive and tensile stresses in the impermeable face. Where, generated stresses exceed allowable values, some cracks would develop in the face and cause deciencies in the performance of CFRD as a water barrier structure. Regarding the fact that the dam body deformation as a result of reservoir imposed pressure, has a direct eect on concrete face deformation, adopting a suitable constitutive model to simulate rockll material behaviour, is of particular concern in predicting deformation and developed stresses in the concrete-face of CFRDs. With regard to the previous works on the behavior of rockll material using large scale test equipments, the behavior of rockll is found to be non-linear, inelastic and pressure dependent which claries the signicance of adoption of a convenient model as dam body material. In this paper, to evaluate the capability of dierent models to predict the deformation of dam body material and subsequence eect on upstream face, two elasto-plastic constitutive models have been selected and calibrated using triaxial test results. After selection of more proper model based on comparison by measured data in Da'ao dam, the performance assessment of concrete-face in terms of maximum deformation and developed in-slope direction strains, under dierent conditions was continued. Two-dimensional analyses wereconducted employing Finite Element Analysis (FEA) software, ABAQUS. This software has the ability of simulating multi-step analysis as applied for modeling of dam body in multi layers, placing the concrete face and applying water pressure of reservoir during impoundment, in this study. The analyses results, revealed the importance of rockll material behavior in the performance of concrete-face, in addition to the remarkable role of dam height and the friction properties of face-rockll interface.

Hammers or presses commonly used in modern manufacturing facilities produce remarkable vibrations during their operation. Foundations supporting these machines experience powerful dynamic effects which may extend to the surrounding areas and affect workers, sensitive machines within the same facility, or the neighboring residential areas. To control free-field impact-induced vibrations, wave barriers may be constructed in the vicinity of the vibration source. This paper examines the efficiency of soft barriers (open trenches) on screening pulse-induced waves for foundations resting on a deep elastic layer or a layer of limited thickness underlain by rigid bedrock. The effectiveness of open trenches as wave barriers is examined for different cases of soil layer depth, arrangement for double trenches, and trench location.A 2D finite element model is constructed and some parametric analyses are performed in the time domain. Different arrangements of wave barriers in vibration isolation for shock-producing equipment are assessed for their efficiency. The results show that using the second trench could remarkably reduce the vibration amplitude. Finally, some guidelines are defined for their use.