I am not sure if this is what you are looking for but this link may be of interest. The terrible conditions that the troops had in the trenches with the mud and everything lead to a condition called 'trench foot'.
for a comic treatment of it, have a look for a Charlie Chaplin DVD of Shoulder Arms, made at the time. At first the studio didn't want to release it, fearing soldiers would be offended by seeing it as comedy, but they turned out to love it. I don't have it to hand but I'm pretty sure some of the jokes were about mud.
Passchendaele (officially the third battle of Ypres) is outstanding among the battles of World War I not only for its cost, but also for the conditions in which those casualties were incurred.
"...I died in Hell
(they called it Passchendaele) my wound was slight
and I was hobbling back; and then a shell
burst slick upon the duckboards; so I fell
into the bottomless mud, and lost the light"
Any website on the Battle of Ypres will give details of the mud and how men and horses drowned in the mud. Here are a couple:
You are in luck as I have just had to write a GCSE coursewwork essay on this! Mud at Passchendaele was the worst part as it rained for 14 days straight (i think). This led to the troops having to walk on duckboards over the water which meant the Germans could machine gun them down. Also, tanks couldnt blast through the enemy lines as they got bogged down in the mud. Also, troops drowned in the mud. A useful point for u here; the tanks corps told British high command not to bombard the area as they realised it would turn into bog. However, they did and then the rain came into it all making the ground and conditions atrocious for the troops. Hope you have fun with your project =D