نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و هفتم شماره 4 (پیاپی 89، زمستان 1396)

The prediction of tunnel convergence at great depth is the important factor in tunneling design. A large number of analytical solutions have been presented for circular tunnels. However; it is not an easy task to use them in practice due to their either complexity or difficulty of stepwise computations, particularly when the stress-strain behavior of rock mass is the strain softening.
Therefore; in this study, a simple analytical approach is presented to estimate circular tunnel convergence using the stress- strain curve of rock mass located on tunnel wall. This curve is obtained based on values of the principle stresses as well as their variation on tunnel wall due to tunnel face advancement.

In the present research, the elastic perfectly plastic and hardening behavior of the sandy soil, located under the inverted folded shell strip foundation, have been modeled in Plaxis software. The analysis is based on the Mohr–Coulomb theory. Moreover, the distribution of internal forces and the effects of variations in the width and thickness of the shell foundations on the bearing capacity have been investigated. The results of the numerical analysis have been compared with the analytical relations proposed by Rinaldi in 2012.

The diffusion of nitrate pollution in watersheds is due to complex biochemical and hydrological procedures linked to the cycle of nitrogen and water. Nitrate load comes from different sources such as wastewater treatment plants, runoff of fertilized lawns and cropland, failing on-site septic systems, runoff of animal manure storage areas, and industrial discharges that contain corrosion inhibitors. Loss of nitrate to surface and groundwater can reduce farm productivity, harm the environment, and affect drinking water quality. Large uncertainties and limited physical understanding of the water quality such as nitrate barricade the process-based modeling and seek a black box relationship between driving and resultant variables. Therefore, in this paper Multi-Station (MS) modeling of nitrate of the Little River Watershed (LRW) has been done. Hence, MS nitrate modeling is considered whereby nitrate loads of the inside and outlet of the LRW could be predicted. As a more explanation, the nitrate of upper sub-basins are employed for predictions of the interior sub-basins nitrate loads, and then, central sub-basins are participated in outlet nitrate prediction of the LRW. So, MS model can prepare a reliable platform to get information about the amount of nitrate in crucial places of the LRW. For this purpose, two scenarios with distinct views are used for MS nitrate modeling to identify the suitable strategy for future hydro-environmental researches. In the first scenario, Markovian characteristics of the streamflow-nitrate process are proposed as the base of the MS model, where antecedent of streamflow and nitrate time series of sub-basins are shared in nitrate modeling. On the other hand, non-linear feature extraction criterion of MI that is more suitable measure regarding the linear measure of Correlation Coefficient (CC) is employed for the selection of appropriate inputs of the Least Square SVM (LSSVM) and Feed Forward Neural Network (FFNN) models to avoid from the time consuming trial-error process of input selection. In the second scenario, seasonality-based characteristics of the streamflow-nitrate process are focused. Where, streamflow and nitrate time series of the sub-basins are decomposed by the wavelet transforms at a suitable level for clarifying spectral and temporal information of the time series. Then, as a new feature extraction method, both SOM and MI are respectively employed for clustering homogeneous sub-series and selecting cluster's proper agents, to be fed into LSSVM and FFNN models for MS nitrate load modeling of the LRW.

During several past decades, many researchers have conducted studies to develop the relationship between liquefaction resistance and seismic parameters of various soils. One of the methods to assess liquefaction which is widely used is the stress-based method, which was presented for the first time by Seed and Idriss (1971) and Whitman (1971). That is an experimental method and is based on experimental and local observations.
Anyway, the relationships developed by the use of the traditional method based on experimental data are limited and don’t provide a proper and stable prediction, they also dont show major weaknesses in mathematical relations, complete structure and heterogeneous space of soil and liquefaction, while soils have quite complicated structures, there is simpler methods of examination that allow unlimited development of a model for all systems, such as genetic programming (GP), artificial neural networks (ANNS) and Neuro-fuzzy inference system (ANFIS) (Shahin et al., 2003). In this study, using fuzzy clustering, it has been initially tried to divide data to groups whose members are similar and have relatively same properties. So data with similar geotechnical and seismic properties can be placed in a cluster and hence, a closer study of the data to better understand the factors affecting soil liquefaction can be possible. Next, a model was presented for time estimation of the soil liquefaction probability using the method of genetic programming. Finally, considering the results of the conducted clustering and the study of data in each cluster, the sensitivity of parameters affecting soil liquefaction and their relative importance were analyzed using nonlinear methods.

The construction industry is known to be the pioneer of countries development. Because of intensive relationship with natural resources, pollution and health topic, this industry has received a great deal of attention in terms of environmental aspects, especially in the recent decades. The impact of this industry on economic and social issues in addition to environmental issues, has attracted the researchers of sustainable development topics on this industry more than before. The construction industry is responsible for the consumption of 40% of global resources, 12% of potable water reserves, 55% of wood products, 45-65% of produced waste, 40% of raw materials, and the emission of 48% of harmful greenhouse gases, which leads to air and water pollution, threat of depletion of natural resources, and global warming (Castro-Lacouture et al., 2009; Roodman & Lenssen, 1995).

In view of potential vulnerability of even exciting buildings designed based on seismic design codes under consecutive strong earthquakes, paying attention to the use of a secure system, especially in earthquake-prone regions is revealed. Tunnel form system is a new industrial construction system in which only the slabs and walls are used as lateral load resisting elements (Balkaya and Kalkan, 2004). Naming this system as the tunnel form is due to the installation of formworks in box manner (Fig. 1) (Mirghaderi et al., 2009).
Previous earthquake experience and the results of laboratory and numerical studies of lateral resistance of tunnel form construction represent a very significant performance against strong earthquakes. So far no study has been conducted to assess the resistance of this construction system subjected to consecutive earthquakes. It seems that this structural system is able to retain safety against successive earthquakes. This study aims to quantify the post-earthquake capacity of the damaged tunnel form buildings after subjecting the main shock and also their performance assessment subjected to multiple earthquakes.

In this paper, our concern is to produce light-weight concrete with using different ingredients in the concrete mix. Specimens were satisfied the density and strength regulators of structural lightweight concretes. The final aim is to increase ultimate strength and effects of added Nano-silica and steel fiber on the mechanical behavior. Nano-silica increases tensile compression and flexural strength with improving the concrete structure (Quercia et al. 2010). In the other hand, using steel fibers reduces the crack width and parallelize their orientation by bridging between microcracks (Qing et al. 2007).

Existing reinforced concrete (RC) frame buildings with non-ductile detailing represent a considerable hazard during earthquakes. These types of buildings suffered severe damages and were responsible for most of the loss of life during the major seismic events. Among seismic performance upgrading methods, several options are normally available, and one of them is to employ energy dissipation devices (Aniello, 2007). Energy input by a strong earthquake is expected to be greatly dissipated by these devices, (Ghobarah, 2001) and if they are damaged, the rehabilitation is quite easy after the earthquake since these devices are designed to be replaceable (Ramadan, 1995). In particular, this paper focuses on removable steel eccentric bracing systems (EBs).

Acid mine drainage (AMD) produced by oxidation of sulphide minerals contained in mining wastes remains one of the critical environmental challenges for the mining industry (Wheeland and Feasby, 1991). The oxidation reaction can cause acidification and heavy metals release in surface and ground water (Dagenais et al., 2005). Use of cover system on mine waste is an effective method for prevention or reduction of acid mine drainage creation (Quangrawa et al., 2005). Use of single layer cover is a method in which the water level remains near the tailings surface (Demers et al, 2009). In this research, the behavior of single cover in controlling oxygen diffusion through cover system was evaluated.

One of the main causes of the destruction of marine structures, is creating erosion in its pier foundation. The uncontrolled spread of scour hole undermines the foundation and thereby will threaten the entire structure. In this study, the performance of countermeasure strategies include bed sill, collar and then combination of them were evaluated. Experimental assessment for cylindrical pier has been conducted under the clear water condition. Based on the recommendations resulting from the studies reviewed, bed sill was attached to the downstream side of the pier, the width of the channel, vertically from floor to sediments and circular collar with an outer diameter equal to 3 times the pier diameter, was installed in the bed level. Also in the combination method the integration of last two solutions was used, while bed sill was placed tangent to the downstream of collar.