Look at B31.1 2004 edition Non-Mandatory Appendix VII "Procedures for the design of restrained underground piping" and have somebody who is familiar with this subject matter guide you through this task on a professonal basis... you are obviously swimming in waters that are way over your head.

In accordance with the NSPE code of ethics you may be in violation of #2 practice beyond your field of competence... see... http://www.nspe.org/ethics/eh1-code.asp