Is it feasible to increase the distance into surrounding clay that heat can be conducted? Could metal be used to conduct heat from clay surrounding tunnels to c

Is it feasible to increase the distance into surrounding clay that heat can be conducted? Could metal be used to conduct heat from clay surrounding tunnels to clay that is presumably cooler, further away? I could imagine that if a material exists that insulates electricity but conducts heat very well, the track itself might be useful in transferring heat to cooler clay, making the track colder and cooling tunnels.