Proceedings of the 4 th World Congress on Civil, Structural, and Environmental Engineering (CSEE’19) Rome, Italy – April, 2019 Paper No. ICGRE 163 DOI: 10.11159/icgre19.163 ICGRE 163-1 Study of Bearing Capacity and Settlement Behaviour of Solid Circular and Hollow Circular Footings on Granular Soil Parth Patel 1 , Manas Bhoi 1 1 Pandit Deendayal Petroleum University Raisan, Gandhinagar, India parth.pcv15@sot.pdpu.ac.in; manas.bhoi@sot.pdpu.ac.in Abstract - This paper presents the experimental study of bearing capacity of isolated model footings which are hollow circular and solid circular in shape subjected to axial loading. The ring footing shape is characterized by outer diameter Do and the inner diameter Di, defined by ring diameter ratio, n= (Di/Do). In this study, behaviour of one solid circular footing (n=0) and four ring footings with n=0.166 (Di=2.5cm), n=0.333 (Di=5cm), n=0.666 (Di=10cm) and 0.866 (Di=13cm) were investigated to analyze the effect of increasing inner diameter while keeping outer diameter constant (Do=15cm). A relationship between load intensity, footing pressure, ring diameter ratio and settlement is developed for each type of footing to determine the influence of the above-mentioned parameters on the bearing capacity and settlement of the footing. These relationships depict that the bearing capacity varies with the change in ring diameter ratio. An efficiency factor is derived from the stress-settlement relation for different ring diameter ratio. It is found that for the hollow circular footings having n=0.166 and n=0.333, the failure pattern is comparable to the solid circular footing having identical bearing capacity and the load-settlement curve, this may be due to the more confining effect up to certain ring diameter ratio; suggesting the use of hollow circular footings over solid footings thereby making savings in volume of material used and the cost incurred. Keywords: Bearing capacity, Ring footing, Load v/s settlement, Footing pressure, Ring diameter ratio, Efficiency factor, Confining effect. 1. Introduction Foundation is an intrinsic and a very essential part of any structure. It transfers the load coming from the superstructure to the underneath soil layer. A structure’s stability mainly depends on its foundation and the type of soil it is resting on. While talking about shallow foundation, different types of footings have different purposes to serve according to their behaviour and characteristics. The shape of different footings such as square, rectangular, circular etc. is chosen depending upon the superstructure and area available for transferring its load to the soil. Hollow circular type footings are a unique case of circular footings which have both inner and outer diameters. These are used in structures which are circular in plan and the transfer of load takes place from walls of building to the foundation before it gets transferred to the soil. Ring or hollow circular foundation can be used in tall circular structures like water storage tanks, bridge piers, transmission towers, oil containers, silos, etc. These all are axi-symmetric structures. Compared to circular footings, hollow circular footing has many advantages and benefits. One is the reduction of the volume of material and the construction cost. Under Dynamic loads, ring footing acts as an anchorage, resisting the slip under dynamic loads. Also the hollow circular footing gives a better stabilizing moment arm when compared to a solid circular footing having same cross-sectional area. Data and literature depicting the characteristics and performance of the ring footings in terms of the settlement and bearing capacity is limited and needs to be explored further. The study of the behaviour of ring footings and its bearing capacity was carried out first by Fisher [1]. Ohri [2], Egorov [3] and more recently Razavi and Hataf [4] have also studied the behaviour of ring footings and its attributes. Many efforts were carried out to obtain suitable mathematical solutions in the form of bearing capacity factors. Kumar and Ghosh [5] used the stress characteristics method to compute the bearing capacity factor Nc for smooth and rough rigid ring footings. Kumar and Chakraborty [5] used finite element analysis along with upper and lower bound theories to determine the bearing capacity factors. Recently, Gholami and Hosseininia [6] and Keshavarz[7] and Kumar [5] derived all three bearing capacity factors for rigid hollow circular footings using stress characteristics method. Numerical analysis through FLAC was performed by Zhao and Wang [8], Benmebarak et al. [9] and