Comments on appropriately backfilling large borehole

[soil1999]

There is 1 ft diameter hole to be drilled to depth of 50 m ( for insatlling some type of casing)adjacent to a toe of a slope dyke. Since there is concern that this hole maybe a potential for concentrated flow (erosion) if not backfilled properly, it is required that a that backfill should be done without voids being left in the hole. Can you pls provide your detalied ,if any regarding this matter (how to gurantee that backfilling did not leave any hole. The only provision I am thinking of that will ensure no voids are left is
- Bentonite should be used and placed with appropraite quantitiy( volume of the hole =volume of the bentoniteused)

 

[Ron]

Inject CLSM (controlled, low strength material) as the casing is removed. Keep the head of the CLSM higher than the expected lateral pressure of the soil. For your purposes, you can probably fill the casing and the extract it almost simultaneously.