The load transfer mechanism in a socketed foundation is a complex interplay of various factors, primarily involving the rock socket wall and the socket base. The distribution of load between these two components depends on several key parameters:
Relative Stiffness: The stiffness ratio between the foundation concrete and the surrounding rock mass plays a significant role. A stiffer foundation tends to transfer more load to the socket base, while a more flexible foundation relies more on the socket wall for support.
Socket Geometry: The shape and dimensions of the socket, including its diameter, depth, and taper angle, influence the load distribution. A deeper socket generally provides more frictional resistance along the socket wall, while a larger base area enhances load-bearing capacity.
Socket Roughness: The roughness of the socket interface affects the frictional resistance between the foundation and the rock. Rougher surfaces tend to develop higher frictional forces, increasing the load carried by the socket wall.
Strength: The strength of both the foundation concrete and the rock mass is crucial. A stronger foundation can withstand higher loads, while a stronger rock mass provides better support and resistance to settlement.
At initial loading stages, with small displacements, the rock-socket system behaves elastically. Load distribution between the wall and base can be determined using elastic analysis methods. However, as displacements exceed 10-15mm, relative movement occurs between the rock and foundation, leading to the progressive failure of the socket bond. This failure reduces the load carried by the rock-socket interface, transferring more load to the socket base.
With further displacement, the interface strength diminishes to a residual value, resulting in a complete rupture of the bond. At this stage, the majority of the load is borne by the socket base, highlighting its critical role in the ultimate load-bearing capacity of the foundation.
Understanding this intricate load transfer mechanism is essential for designing and analyzing socketed foundations effectively. By carefully considering the various factors that influence load distribution, engineers can optimize the foundation’s performance, ensuring its stability and long-term durability under various loading conditions.