زمینه و هدف: استفاده از انواع مختلف آجر به عنوان مصالح ساخت و ساز برای سالیان زیادی مورد توجه بشر بوده است. استفاده از مصالح خاکی در مقایسه با سایر مصالح صنعتی تاثیرات مخرب زیست محیطی کمتری دارد. هدف کلی این مطالعه مقایسه میزان انتشار کربن و محاسبه انرژی مصرفی در طول چرخه حیات مصالح خاک کوبیده و آجر رسی پخته شده (آجرهای سنتی) و بررسی تاثیرات زیست محیطی مربوطه می باشد. درنهایت سعی شده است با استفاده از نتایج مقایسه کل زنجیره تولید تا دروازه این دو نوع مصالح، پیشنهاد ساخت و ساز با حداقل اثرات مخرب زیست محیطی و در جهت تامین اهداف توسعه پایدار ارائه گردد.

روش بررسی: روش ارزیابی چرخه حیات در این تحقیق مبتنی بر استفاده از ضوابط و توصیه های استاندارد معتبر ایزو 14040 می باشد. مطابق این استاندارد جهت ارزیابی چرخه عمر به بررسی تک تک دروندادها و بروندادهای زیست محیطی در سراسر چرخه حیات محصول یا خدمت از ابتدای تولید تا انتهای عمر بهره برداری توجه ویژه می گردد.  محل انجام این پژوهش شهر کاشان می باشد.

یافته ­ها: بر اساس مطالعه انجام گرفته در شهر کاشان دیده شد که به ازای تولید هر یک تن آجر رسی پخته شده در کل زنجیره چرخه حیات، میزان انرژی مصرفی و انتشار کربن به ترتیب معادل 4804 مگاژول و 1287 کیلوگرم گاز دی­اکسیدکربن است. در مقایسه، برای یک تن ازخاک کوبیده شده، فقط 158 مگاژول انرژی مصرفی و تنها 42 کیلوگرم گاز دی­اکسیدکربن انتشارمی­یابد. بدین ترتیب استفاده از خاک کوبیده در مقایسه با آجر رسی موجب کاهش 1245 کیلو گرم بر تن تولید گاز دی اکسید کربن و 4646 مگاژول بر تن انرژی مصرفی، یعنی کاهشی بیش از 95درصد می­شود.

بحث و نتیجه ­گیری: کاربرد خاک کوبیده در مقایسه با آجر رسی می­تواند به میزان قابل ملاحظه­ای درکاهش اثرات منفی زیست محیطی ساخت و ساز اثر گذار باشد. علاوه بر این برای صاحبان و سازندگان مسکن، انرژی مصرفی و انتشار کربن مضر از آجر رسی پخته شده به عنوان مصالح متداول ساخت و ساز را مشخص می­کند.

تفاصيل المقالة

The number of constructed dams has been largely increased due to high demands of water supplies, and earth dams are the most common types since they are more compatible to the environment. Nevertheless, the stability of these important structures during earthquakes has to be carefully evaluated and guaranteed. In the past, earth dams usually designed with pure clay core, but in recent decades they are widely designed and constructed with mixed clay core due to their better performance against vibrations particularly earthquake loadings. This paper evaluates the displacement performance of the Karkheh Large Embankment Dam with mixed- clay core, recently constructed in south-western part of Iran, under earthquake motions and compares the dynamic analyses’ results with those of pure-clay core. In this work, the Karkheh Dam with both mixed and pure clay core is numerically modeled using the FLAC 4.0software. After calibrating the model and completing the static and dynamic analyses under different excitations, belonged to some heavy past earthquakes, the results in terms of the maximum settlements, horizontal displacements of upstream and downstream shells are estimated, compared and discussed. Based on the obtained results, it is noted that the dynamic performance of earth dams with mixed-clay core is more desirable than that of pure-clay core. It is also observed that the seismic settlements of the dam with pure-clay core averagely show an increase of 20 percents compared with that having the mixed-clay core. تفاصيل المقالة

The hydraulic pressure is one of the most important factors in the design of pressure intake tunnels. Since the surrounding media cannot usually resist the high internal pressure of these tunnels, they are usually finished with an adequate lining mostly of reinforced concrete, which is an interaction problem between water, soil or rock and concrete lining. Although reinforcing the concrete lining may reduce the width and number of the developed cracks in the lining, the penetration of water into the surrounding media can still happen due to high water pressure in the tunnel. Thus, it may lead to the development of hydro pressure on the external surface of the lining. There are some theoretical methods that are developed for the design of tunnel lining in this condition. When the tunnel is located above the underground water table, the seeping water may lead to strength reduction of the adjacent soils, particularly when the ground, like the mudstone layers existing in Dasht-e-Abbas region, south-west of Iran, is cohesive and consists of soils that are susceptible to water. In this paper, the hydrostatic interaction between soil and concrete lining of Dasht-e-Abbas pressure intake tunnel has been investigated when the shear strength parameters of the mudstone layers decrease due to the seepage of water to the surrounding media. To evaluate the stability of the tunnel, a two dimensional numerical simulation is developed using the finite element code called PLAXIS and interaction analyses are carried out. The analyses are done in stages to assess the maximum internal forces induced in the lining. The structural stability of the tunnel is evaluated and discussed in this condition. Based on the obtained results, it is noted that for more realistic understanding of the behavior of infrastructures like pressure intake tunnels under various conditions, numerical analyses should also accompany experimental and analytical approaches such as Schleiss method which is described in this paper, especially for tunneling in media that is susceptible to water and ground strength reduction. The numerical analysis results show a considerable increase in the lining internal forces when subjected to the reduction of ground strength. However, the tunnel structure is still stable under the effect of surrounding ground degradation with the constructed lining specifications. تفاصيل المقالة