The container holding the soil was 6 by 12 by 24 inches high. The depth 

 of soil was 18 inches leaving 6 inches available at the container top 

 for pile positioning equipment. 



The low void ratio soil placement procedure also used a disbursing 

 box and a 1/2-inch Tyler sieve screen. In order to achieve a 1-inch 

 higher density lift, additional soil was added and tamped by a 

 3- by 3-inch square wooden hammer. The following void ratios were ob- 

 tained for the suite of soil models: 



Model High Void Ratio Low Void Ratio 



Calcareous Sand 2.0 ± 0.1 1.4 ± 0.1 



Calcareous/Silica Sand 1.43 ± 0.01 0.94 ± 0.02 



Silica Sand 0.75 ± 0.1 0.6 ± 0.1 



A total of 18 inches of soil required 18 lifts. In between each 

 even lift, 13 lead shot pellets were placed on the surface of the lift. 

 Three pellets were placed, 1/2 inch apart, directly on the center line 

 of the pile driving path with the center pellet on the center line of 

 the pile. The remaining 10 pellets were placed symmetrically on each 

 side of the pile in a geometric progression manner starting with 1/4 inch 

 from the pile surface and stopping at 4 inches. The finished model, had 

 eight layers of 13 lead shot pellets for a total of 104 discrete points. 

 The size of the pellets was compatible with the median soil grain size 

 determined from the grain size distribution curve (Figure 3) . 



Test Procedures 



Thirty-four sand models were constructed and tested to determine 

 the driving energy required to penetrate the sand and to monitor the 

 vertical and horizontal movement of each lead shot pellet by radiography. 

 Cured sand models were taken to the Aeronautical-Mechanical Prototype 

 Support Branch at Point Mugu and set up in front of the x-ray equipment. 

 A metal grid, for monitoring relative movement, was tacked to the back 

 of the wooden container (model) and a pile guide secured over the soil. 

 An x-ray* was taken showing the initial position of the lead pellets. 

 The pile driving mechanism was placed in the guide and a selected weight 

 fell 30 inches and impacted the top of the pile. A second x-ray was 

 taken after the pile was driven 2 inches (Figure 5). This process was 

 repeated until the pile had been driven 14 inches. In a few cases, the 

 high cementation sand models were too hard for the piles to be driven 

 14 inches. The hardened material caused severe cracking of the soil 

 mass and container failure from the driving energy. When this occurred, 

 pile driving was stopped. After the pile reached full penetration, a 

 pullout test was done but the load was not measured. 



*The word "x-ray" implies that film, placed behind the model, was 

 exposed to the x-ray source that recorded the position of the grid, 

 lead shot pellets, and the pile. 



10 



