تحليل عددي شمع سرگيردار مدفون در خاك، جهت برآورد رابطه ي ظرفيت باربري جانبي

Numerical Evaluation of Lateral Bearing Capacity for Fixed-Head Piles

امروزه پي هاي شمعي در سكو هاي دريايي، پل ها، و سا ختمان هاي بلند استفاده ي وسيعي دارند، كه بايد در برابر نيرو هاي جانبي ناشي از زلزله، باد، موج دريا، و ... مقاومت كنند. تاكنون براي تخمين ظرفيت باربري جانبي شمع ها عموماً از منحني p-y مبتني بر آزمايش‌هاي صحرايي استفاده شده است. با وجود اين، ارايه ي يك رابطه ي عمومي ظرفيت باربري جانبي (مشابه ظرفيت باربري قايم) براي شمع ها، يك نياز اصلي در مهندسي ژيوتكنيك است. در اين پژوهش، با انجام تحليل هاي سه بُعدي غيرخطي بر مبناي روش اجزا محدود به كمك نرم‌افزار OpenSeesPL، رفتار شمع سرگيردار تحت بار جانبي استاتيكي در خاك ماسه‌يي مورد ارزيابي قرار گرفته است. همچنين عوامل تاثيرگذار در ظرفيت بار بري شمع، از قبيل: مشخصات هندسي شمع و پارامتر هاي ژيوتكنيكي خاك از قبيل مورد بررسي قرار گرفته است . همچنين ميزان تاثير اين پارامتر ها ارزيابي و درنهايت، رابطه ي پيشنهادي ظرفيت بار بري جانبي استاتيكي شمع هاي سرگيردار در خاك ماسه يي ارايه شده است.

Piles are used extensively to resist lateral load from earth pressure, inclined load, wind, waves, earthquakes, etc. The behavior of piles subjected to lateral loads is governed by interaction between the pile and the soil, and it is a non-linear, three-dimensional soil–structure interaction problem. Pile properties, including pile stiffness and geometry, and soil properties, i.e., unit weight, stiffness, friction angle, cohesion and the pile/soil interface, play important roles in the response of piles subjected to lateral loads. Existing methods for the analysis of laterally loaded single piles can be generally classified into the following five categories: (1) the limit state method; (2) the subgrade reaction method; (3) the p–y method; (4) the elasticity method; and (5) the finite element method. However, the effect of fundamental soil properties (e.g., strength, stiffness, and volume change characteristics) on the response of pile and soil cannot be appropriately addressed in these methods. Thus, an investigation into the effects of fundamental pile and soil properties on the soil response of a pile subjected to lateral load is necessary and helpful in improving insight into the soil/structure interaction problem for a laterally loaded pile. A fundamental study into the soil/ pile interaction response of fixed-head piles subjected to static lateral loads in sands is conducted using the non-linear finite element approach. The effects of pile properties, i.e., length and diameter, and soil properties, i.e., the horizontal coefficient of earth pressure, unit weight and stiffness, on the pile response of a pile subjected to lateral load, are also investigated. In the numerical model, the pile was treated as a linear elastic material and the soil was idealized using the multi-yield-surface plasticity model with a non-associated flow rule. The improvement in pile lateral load was found to be strongly dependent on the pile diameter, soil friction angle, and relative density of the sand. It was also found that the effective embedment length of the pile is more effective than the total length of the pile. Based on the numerical results, effective parameters are discussed and a formula for the lateral bearing capacity of a fixed-head pile in sand is recommended.