Cliff Reinforcement

[nadd]

Problem: A transmission tower was built near a cliff and this past few months due to heavy rains, parts of the cliff have eroded. So cliff reinforcement in in order. The tower's leg is about 8m from the edge. The cliff is about 19m high with a creek about 3m wide at the bottom. The cliff has a near vertical slope. I am lookng at soil nailing technology to reinforce the cliff. Got any good ideas? Thanks.

 

[Jim6758]

You could install "deadmen" or soldier piles between the tower leg and the cliff. The depth required will depend on the nature of the soil. These are piers or piles in close proximity to one another(say 8 to 10 inches apart. It is important to use a "tremie" when placing the concrete so that you don't get aggregate/paste separation. If the erosion continues, you can hang a concrete wall on the "deadmen" to prevent additional erosion.

 

[excon]

i had to deal with a similar problem, only difference it was a communication tower for cable&wireless, around 60 meters and it was about 2 meters from the edge.There was a land slide that made that edge a vertical cut.
first , to keep all the underground water away from the cliff, we constructed a underground drainage, with geotextile, crusched rock, and perforated pipes , as close as possible to the edge. Then with the help of a Samsung 280 excavator we constructed a series of benches to distribute the weight, also we constructed some culverts to keep the water from running over the slopes in quantities, also all the surrounding area around the tower was covered with a thing slab of concrete to prevent water to get into any crack of the soil and further water accumulation underground. These measures were taken a year ago, and the land slide and the erotion stopped, so i hope that some of these can help you, i have a problem too, and i posted it so if you can take a look i will appreciate it.

 

[dtatlow]

You could try to set screw piles to stabilize the slope with a retaining wall application. Check out

http://www.peacelandpiling.com

 

[dirtsqueezer]

I agree with excon's suggestions for stabilizing the slope by mitigating runoff. I also think that if your river is undercutting the cliff base, there is a chance your slope may fail by being undercut at the toe.
We have had success locally containing rivers that run through residential neighborhoods using rock baskets.
A rock basket is a simple cage made of galvinized fencing that is filled with river rock and can be stacked to form a wall. They're not pretty, but it's cheap. In your case, they may be of use on the outside bend of the river, dissapating the energy of the river, and preventing erosion at the toe of the slope. If the soil is stable enough to be cliff-forming, it sounds like you have a good chance of success.
I would be interested in a follow-up to this discussion on how it turns out. Best of luck.

 

[Jim6758]

I would caution that "rock baskets" which are properly called gabions are not so cheap if done correctly. All the stone should be about the same size(4 to 6 inches in diameter) and the base and top should be hand placed by people who know what they are doing. Done properly, it is somewhat labor intensive, but very attractive. Make sure that the gabions are set on a solid base and not subject to undercutting. I still think that deadmen installation is the cheapest way to go.