مدلسازی آزمایشگاهی- عددی رفتار لرزه ای شیب های ماسه ای خشک مسلح شده با ردیف شمع

در این مقاله رفتار دینامیکی شیب خاکی متشکل از مصالح ماسه ای خشک سست توسط مدل های کوچک مقیاس فیزیکی و عددی مطالعه می شود. ردیفی از شمع های شناور مدل آلومینیومی درون شیب ماسه ای ساخته شده در جعبه ی صلب و شفاف مدلسازی فیزیکی روی میز لرزه نصب شده اند. میز لرزه ی کوچکمقیاس دو درجه ی آزادی با منشا ارتعاش الکترودینامیک به کمک سنسورهای اندازه گیری شتاب و تغییرمکان ابزار بندی شده است. در این تحقیق به شکل نوآورانه ای، بارگذاری لرزه ای هارمونیک یک بار در راستای طولی شیب، یکبار در راستای عرضی شیب و بار دیگر به طور همزمان در هر دوی این راستاها اعمال شده است. مقادیر پاسخ های نشست تاج شیب که به کمک سنسور lvdt در هر یک از این حالات بارگذاری اندازه گیری شده اند، به عنوان منحنی های خروجی ارائه شده اند. در پایان مقاله، جهت صحت سنجی نتایج مدل فیزیکی کوچک مقیاس، مدل عددی تفاضل محدود سه بعدی نظیر آن ایجاد شده است. هماهنگی و توافق مناسبی بین نتایج عددی و آزمایشگاهی بدست آمده است. نتایج این مطالعه نشان می دهد که افزایش راستای بارگذاری شیب از حالت مرسوم یک محوری به دو محوری و نیز عدم تسلیح شیب با ردیف شمع، باعث افزایشی چشمگیر و بیش از 100% در مقادیر تغییرمکان های قائم خواهد شد.

Experimental-Numerical modeling of seismic behavior of dry sandy slopes reinforced by piles row

In this study the behavior of floating piles row with circular crosssection were installed inside the dry sandy slope by help of threedimensional numerical analyses and physical modeling have been simultaneously studied. The threedimensional numerical modeling was used for conducting the parametric studies about effects of directions of imposition of harmonic seismic loading on the main geotechnical parameters of floating piles rowsandy slope problem. The seismic loading of harmonic sinusoidal waves in the form of seismic motions in the inplane and outofplane directions along the longitudinal and transverse directions of slope model and both of them were imposed on the slope physical and numerical models. Moreover, the physical modeling of the investigating problem was implemented for validation of numerical results by imposing the sinusoidal harmonic loading in the longitudinal and transverse horizontal directions of microscale slope model by help of smallscale geotechnical shaking table. Reinforcing of a dry sandy slope by a row of floating piles (similar to reinforcing of slope by endbearing piles row) results in significant decrease (to about more than 50 percent) in slope rsquo;s vertical displacements. Outofplane components of seismic loading such as transverse component of earthquake, T component, (productive of horizontal shear waves, i.e., SH waves) also in the presence of site rsquo;s effects such as ldquo;directivity effects rdquo; can produce the responses as large as the inplane motion components such as earthquake longitudinal contained component, L (productive of P and SV seismic waves). The motion of slope sliding wedge in the strong ground motions is a rigid block motion while the failure wedge displacement under weak ground motions is a negligible motion and occur in a flexible block manner. Simultaneous seismic loading along twoaxes of three coordinate axes in contrast to the current slope seismic loading that the seismic loading are imposed along one axis and in the longitudinal direction of slope failures surface, have great effects on the slope displacements values and internal efforts generated in the reinforcing piles row. Studying and solving the classic problem of inplane and outofplane seismicwaves propagations in the combination with the existence of slope in the ground and piles row interaction (i.e., adding the piles rowslope seismic interaction to the initial classic problem) by help of present available analytical and mathematical solutions will be a very difficult problem. By combining of the inplane and outofplane seismic motions the complexity of the piles rowsandy slope dynamic interaction problem will increase and in the some cases presenting analytical and closedform solutions can be impossilble. The alternating solutions for solving these complex problems proposed by the present paper are the simultaneous using of numerical and shaking table physical modeling for understanding the precise details and ambiguities of the problem in the complete scientific and practicalempirical frameworks. The results of present study show that installing a row of floating piles similar to the endbearing piles row can reduce the displacements of loose dry sandy slope and through this manner the seismic stability of slope against the local and general failures increased. In the present paper despite of increasing the directions of seismic loading from onedirection to the twodirections the installed floating piles row sufficiently played their roles in the reducing seismic displacements of slope. Indeed, according to the experimentalnumerical results of the present paper, decreasing of slope crest settlements by installing a row of floating piles in the seismic loading cases are more than 50 percent. The results of smallscale 2DOF geotechnical shaking table physical model were used to verification of the obtained 3D numerical results. There is a good agreement between the numerical and physical models results.