The existing theories have been developed for more than 20 years,however mainly focus on linear problems (Bishop and Price, 1979; Wu, 1984; Du, 1996;Wang, 1996).

• 水弹性理论至今已发展了20多年，着重研究线性问题（Bishop & Price，1979；Wu，1984；杜双兴，1996；王大云，1996）。