Maybe I can not express clearly,  I point out something that I don't understand, you will know what I mean.I put the pictures in attachment named figure 1-7.
1.From the figure 3 and figure 4.the stress is a constant,it worked.
2.From figure 2, the left boundary loaded a porewater pressure function and the right loaded a pressure--a constant equal 1000.but the figure 2 show the right pressure is 0.
3.From figure 6 and 7. if the value in two function is equal,both they are p=p2=9.8*10e3*z, it worked,we can see it from the figure 6.but if it is unequal, p2=9.8*10e2*z, the figure 7 show the right pressure is 0.