Q1: Large diameter sewers subjected to external pressure alone, are reinforced

ANS:D - with elliptical cage

The use of an elliptical cage in reinforcing large diameter sewers is not a standard practice. Typically, reinforcement for sewer pipes subjected to external pressure alone involves methods such as adding steel reinforcement cages or ribs near the outer surface of the pipe, encased in concrete. An elliptical cage is not commonly used for this purpose. However, if we were to imagine the concept, an elliptical cage would be a structural reinforcement in the shape of an ellipse, designed to fit around the exterior of the sewer pipe. This cage would provide additional support and strength to the pipe, helping it withstand external pressure from the surrounding soil and other environmental factors. While the idea of an elliptical cage might seem feasible in theory, it is not a widely recognized or utilized method in sewer pipe reinforcement. Instead, traditional methods such as steel reinforcement cages or ribs are more commonly employed due to their effectiveness and reliability in reinforcing sewer pipes subjected to external pressure. Therefore, while an elliptical cage could potentially provide reinforcement, it is not a standard practice in sewer pipe construction or reinforcement.