What is the coefficient of restitution for the pile and cushion?

The pile would have no loss of energy so EEM(i) = 1.00 for all pile springs.

Coefficients of restitution and other properties for cushions are listed on the 686 page under “Additional Students Resources (ASR)” in the “Data and help files”, part C, Cushion properties.

What is gamma?

The meaning and appropriate values are listed in the user’s manual in the ASR section M. See the figure on page 40, and for an explanation of limiting forces between pile segments see page 45.

Total static load resistance?

Sadly, in a wave equation problem the total static soil resistance (RUT) starts out unknown. You just have to make a guess and see what the program spits out. If you put RUT = 500 kips and the program tells you that you are advancing the pile at 1 blow per foot, you put way too low a RUT value for your first guess. Increase the resistance. If instead it says you are getting 5000 blows per foot, you put way too much resistance. You must then adjust the value of RUT up or down so you start getting practical blow counts from around 20 to 200 blows per foot.

RUP: Along with RUT = 500 kips, if some of that total resistance goes under the point of the pile, you will have to put how much goes under the point as RUP (resistance under point). So if your soils consultant says that 20% of the total resistance on the pile goes under the point, and you put RUT = 500 kips, you would enter RUP = 100 kips.

What do I use for the pile weights?

Calculated in class. Also see section the ASR section M page 52.

What is MO, the number of elements upon which soil resistance acts?

No, MO is the weight number of the first element upon which soil resistance acts. See ASR section M, page 51 for definition of MO. It is the mass number that corresponds with the first soil spring resistance. See also the figure on page 60, where MO = 6.

Dr. Lowery,

I have several questions regarding the input for homework 1.

- For gamma 3 on Card 102, is this value -1.0 since the pile is continuous thus tension is expected in between segments? That is correct.
- Provided no soil information, would it be fine if we assume the soil strength/ static load acting on soil (RUT)?

That is correct, although if you are driving in a soil subject to set-up (soils in which the resistance increases with time to a higher value), you will probably take the static resistance predicted by the soils consultant, divide it by the set-up factor, and use that for RUT and RUP, the resistance to penetration at the time of driving.

- The 20% resistance at pile tip, is this 20% of embedment length or the 80% resistance is for the whole 200-ft embedment length?

If RUT = 500 kips as a first guess, then RUP is 20% of that number.

- For card 200, is the second weight provided in the example due to the helmet weight? Also, in computing the third weight, it appears in class that we assigned the total weight at last pile segment. Shouldn’t this be weight of each pile segment?

Yes, the second weight in your problem will be the helmet weight. And yes, we used to put in EVERY weight, one at a time. How dumb. On the new input image, if your 3rd through 440th elements all weigh 6.391 kips, you just tell the program that W(440) = 6.391 and it understands that weights 3 through 440 = 6.391 kips. If you have another 100 feet of pile left to go, which is heavier, just tell him the last weight in that string of weights – W(450) = 7.126 kips. Saves time and paper, and is pretty easy to input your data. All of the other long form input cards work the same way.

- Do we obtain the spring rate for the steel similar to obtaining spring rate for the cushion?

Yes. K = A*E/L and watch your units.