Tunnel boring machines (TBMs), also known as moles, are used to excavate tunnels with a circular cross-section through various ground conditions ranging from hard rock to sand. TBMs provide alternatives to conventional drilling and blasting or hand mining techniques, limiting disturbance to surrounding ground and producing a smooth tunnel wall. Key advantages of TBMs include higher advancement rates, continuous operation, less rock damage, reduced support needs, greater work safety, and automated processes, though TBMs themselves can be expensive to construct and transport.