Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations waross on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Grouting in vertical fissures in rock

Status
Not open for further replies.

sgsibob

Geotechnical
Apr 15, 2002
31
US
Isn't the resultant fluid force on a vertical boundary limited by the volume of fluid available to exert the force?

I am going to use an example of a fissure in rock but the same could be said of a retaining wall with a finite amount of flowable material behind it, for example a wall cut into rock with a narrow zone of structural backfill behind the wall face.

Let's say one has a vertical fissure in impermeable, unsaturated rock and one wants to grout the fissure to stabilize the column of rock between the fissure and a nearby free surface. While the grout is still fluid, the fissure walls will theoretically be subjected to a hydrostatic pressure per unit of wall length equal to 0.5*(height^2)*fluid unit weight. For example let's say (for simplicity) the grout has the density of water and the height is 10 ft; then the theoretical horizontal fluid pressure on the fissure walls is 0.5*62.4*100 = 3120 lb/LF of fissure. Now let's say the fissure is only 1 inch wide. It contains only 1/12*10*62.4 = 52 lb/LF of fluid. As I said the fissure contains fluid, but the walls are dry and impermeable, so there is no hydraulic communication between the fluid in the fissure and any other fluid level.

I see these analyses all the time where the hydrostatic pressure is used, even though it exceeds the weight of the water available to exert it?

Am I missing something here?
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor

Back
Top