بررسي آزمايشگاهيِ تأثير ميزان چسبندگي در پايداري شيب هاي خاكيِ مسلح با ستون سنگي

Experimental Studies of Cohesion Effect on Stability of Soil Slopes Reinforced with stone column

پايدارسازي شيب هاي طبيعي يكي از مسائل حائز اهميت در مهندسي ژئوتكنيك مي باشد. استفاده از راهكار هاي مفيد، ساده و مقرون به صرفه در پايدار سازي شيب هاي خاكي ضروري است، چرا كه امروزه در طبيعت با توجه به پيشرفت و توسعه ي ساخت و ساز در نواحي شيب ها، پايدار سازي شيرواني هاي مشكوك و كسب اطمينان از مقاومتِ كافي آن ها در برابر بارهاي وارده يكي از چالش هاي اساسيِ پيش روي مهندسين مي باشد. استفاده از روش هاي متداولِ پايدار سازي شيرواني ها بسته به شرايط محيطي، اهميت محل مورد نظر و درجه ناپايداري آن، هزينه هاي مصرفي مصالح موجود، امكانات و غيره بسيار متنوع مي باشد. يكي از روش هاي متداول و مناسب براي مسلح كردن شيرواني هاي خاكي استفاده از ستون هاي سنگي مي باشد. هدف از انجام اين پژوهش مطالعه ي آزمايشگاهيِ بررسي مقدار چسبندگي بر پايداري شيرواني هاي خاكيِ مسلح با ستون سنگي است كه نتايج حاصل از آن علاوه بر جديد بودن به عنوان يك كار پژوهشي تامل برانگيز مي باشد؛ اين كار با استفاده از ساخت مدل شيرواني ماسه اي و اشباع آن به كمك بارش و سپس اعمال بارگذاري صورت گرفته است. سپس نتايج به دست آمده به كمك روش اجزاي محدود (نرم افزار PLAXIS2D) و روش تفاضل محدود (نرم افزار FLAC3D) مورد تائيد قرار گرفته است. نتايج آزمايشگاه و تحليل هاي عددي نشان داده اند كه 5 درصد خاكِ ريزدانه ي چسبنده تاثير چشمگيري در افزايش پايداري شيرواني مسلح شده با ستون سنگي دارد. نتايج به دست آمده از تحليل هاي عددي تطابق خوبي با مدل سازي هاي آزمايشگاهي دارند.

The increasing demand for engineered cut and fill slopes on construction goals has increased the need of understanding the analytical methods, investigation tools and the most important stabilization methods to solve slope stability problems. The first step to maintain the stability of soil slope is performing excavation in the slope crest or/and filling the slope toe. This is the cheapest method for stabilization of soil slopes. If the method cannot provide the required factor of safety, it is necessary to use other stabilization methods. Numerical and laboratory approaches are useful for modeling soil slopes stabilization. Modeling the stability of earth slopes using numerical methods is a common practice in geotechnical engineering. Moreover, stabilization of soil slopes using piles has been practiced by many researchers in numerical and analytical approaches. Although numerical and analytical methods have special capabilities, laboratory modeling is more reliable. Stability slope analysis has attracted lots of researchers around the world and it shows the significance of this matter. When suspicious about stability of soil slopes, immediate actions and preventative steps should be used for suppression of instability occurrence. Many projects intersect with valleys and rides, which can be prone to slope stability problems. Natural slopes that have been stable for many years may suddenly fail because of many reasons; therefore, finding useful techniques for stabilizing them is a great concern for geotechnical engineers. In all soil slopes, the primary way for stabilization is the excavation in slope crest and/or filling slope toes. If this would not increase safety factor, other procedures should be applied. Three common styles of stabilization methods are; vertical reinforcement (such as stone columns and piles), horizontal reinforcement (like Geo-grids), oblique reinforcement (such as nailing). One of the common methods that is used to increase the safety factor of slopes is stone columns. All of the experimental tests were modeled and compared using the limit equilibrium (LE) and finite element (FE) methods, which are compliant with each other. Understanding soil properties is crucial for analysis of soil slopes. In this study, the effect of cohesion in embankment is investigated. This is carried out by performing laboratory tests and using finite element method software (PLAXIS2D) and finite difference method software (FLAC3D). A sand slope is reinforced with a stone column at the middle of slope. It is then saturated by precipitation and loaded up to the failure. Experimental studies in this article have the potential to give valuable information about the effects of embankment cohesion and penetration depth of stone column into the stiffer layer, in stability of stone column reinforced soil slopes.