كليدواژه :
بيوراكتور غشايي , فاضلاب پتروشيمي , كاهش گرفتگي , جاذب كربن فعال
چكيده فارسي :
پيهاي گسترده در خاكهاي ماسهاي به طور معمول از ظرفيت باربري بالايي برخوردار بوده ولي ميزان نشست در اين خاكها ظرفيت باربري مجاز
پي را محدود ميكند. امروزه به كارگيري پيهاي شمعي به عنوان راهحلي براي كاهش نشست بسيار رايج است. در چنين شرايطي سهم بيشتر بار به
پي گسترده وارد ميشود و شمعها نقش كاهنده نشست را خواهند داشت. تعداد شمعهاي استفاده شده و محل قرارگيري آنها به گونهايست كه
نشست پي را به مقدار مجاز كاهش دهد. اندركنش ميان شمع– خاك– پي گسترده در پيشمع پيچيده است. كارهاي تحليلي و عددي فراواني در
مورد پيهاي شمعي انجام شده ولي كارهاي آزمايشگاهي نسبتاً اندك است. در اين مقاله با مدلسازي فيزيكي بارگذاري فشاري پيهاي شمعي در
آزمايشگاه و نيز با كمك تحليل عددي اجزاء محدود به ارزيابي رفتار اين پيها در ماسه خشك پرداخته است. شمعهاي مورد آزمايش و پي گسترده
به صورت بتني درجا اجرا شدند. مدلهاي فيزيكي استفاده شده شامل شمع منفرد، شمع منفرد واقع در گروه شمع، پي گسترده و پيشمع بودند.
همچني اثر مقياس مدل فيزيكي روي نتايج مورد بررسي قرار گرفته است. نتايج نشان داد كه وقتي شمع منفرد توسط شمعهاي ديگر محصور
ميشود، ظرفيت باربري آن افزايش مييابد. همچنين با افزايش تعداد شمعها در زير پي گسترده مقدار نشست پي به طور قابل ملاحظهاي كاهش
يافته است. با كمك مدلسازي عددي و نيز بكارگيري نظريه حالت بحراني ميتوان با دقت قابل قبولي از نتايج مدلسازي فيزيكي با ابعاد آزمايشگاهي
در مقياس واقعي نيز بهره جست.
چكيده لاتين :
Nowadays, the employment of large raft foundations is common in high-rise buildings. The amounts of
settlement in these cases usually are considerable. The settlements are reduced by installation of some piles
beneath the raft, occasionally. This load transfer system is called “piled raft Foundation”. In such cases, the
raft usually carries a high portion of structural loading, and the piles are as the settlement reducer elements.
The number of piles and their configuration are determined in such a way that settlement of the foundation
decreases to an allowable value. In these situations, the configuration of piles is determined in optional manner
and strategically. The foundations are conventionally designed in which the piles carry the total load of
structure and the raft bearing capacity is not taken into account. Numerous studies indicated that this method
is too conservative and the load should be divided between piles and raft. Only when the pile cap is elevated
from the ground level, the raft bearing contribution can be neglected. In a piled raft foundation, pile-soil-raft
interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors
of piled raft foundations, very few experimental studies are reported in the literature. As long as the behavior
of these foundations is not evaluated on experimental or full-scale tests, it cannot rely on analytical and
numerical results. Full-scale loading tests are costly due to the large amounts of forces and reactions.
Therefore, the small-scale experimental study can be an effective way of controlling numerical and analytical
methods. This paper concentrates on study of behavior of piled raft in dry sand by physical modeling and finite
element analysis method. The piles and raft models were made of cast-cast-in-place concrete. The physical
models consisted of single pile, single pile in group, unpiled raft and piled raft foundation. The scale effects
of the models were investigated. Some instruments measured the load contribution between the piles and the
raft. The effect of the piles installation in the group was also investigated. The results showed that with
installation of the single pile in a group, the pile bearing capacity and stiffness increase. In fact, the piles
installation and confinement, increases stiffness of the soil around the pile that decreases soil deformation and
pile settlement. Due to increase of the number of piles beneath the raft, the bearing capacity of raft increase
and its settlement decrease, significantly. By increasing the number of piles, the settlement of the foundation
decreases significantly. At the beginning of the loading, due to higher stiffness of the piles than the soil, the
slope of load-settlement curves for the piled raft is greater. The piled raft with maximum number of piles has
a steeper initial slope in the loading curve. After pile failure, the loading curve reduces and becomes parallel
to that of unpiled raft. Based on the results of this study, with the use of finite element method and the critical
state theory, one can predicate behavior of test model in the full scale dimensions.
