• Use a hammer (or another means) to force the end of pile into 

 the concrete or grout. 



« Pour in more concrete or grout to complete the pile installation. 



The equipment used to remove the internal plug and to form a belled end 

 is available and can be easily adapted for this system. 



Modified Drilled and Grouted Piles (MDGP) 



As shown in Figure 33, this system is a slightly modified version 

 of the conventional drilled and grouted piles. The pile wall in this 

 system is perforated and an oversized drill bit is attached at the tip 

 of the pile. The pile and drill bit are moved forward at the same time 

 to the correct depth. (No drilling mud is used, thus avoiding mud con- 

 tamination.) The drill bit is removed and grout from inside the pile is 

 forced out through the holes to fill the annulus. On some occasions the 

 hole could collapse during drilling and prevent the pile being inserted. 

 If this happens either a vibratory or impact force may have to be used 

 to insert the piles. 



Keyed-in Piles (KIP) 



As shown in Figure 34, this system uses a specially designed pile 

 with a mechanical keying-in system equipped with lateral extension 

 branches that are pushed out through the piles and into the surrounding 

 sediment after the pile has been driven or installed by vibratory hammers. 

 Either hydraulic or mechanical systems can be used to push out the ex- 

 tension branches. Axial loading will force the extended branches to 

 form a different and more complicated failure pattern in the soil than 

 the conventional piles. Additional load carrying capacity in either 

 axial compression or pullout is expected for this system. 



More development work is needed before this system can be used. 

 Several aspects require further evaluation; they include, but are not 

 limited to, the following items: 



• Understand the failure mechanism governing the load carrying 

 capacity of this piling system in a variety of calcareous 

 sediments. 



• Determine what effects the keying-in system will have on the 

 axial behavior of this system. 



• Design and implementation of keying-in and pushing-in systems. 



Drilled and Screwed Piles (DSP) 



This system is very similar to the Fundex piles used in Europe 

 (Tomlinson, 1977). This system (Figure 35) uses an expandable helically- 

 screwed drill point held by a bayonet joint at the lower end of a tube. 

 The tube is rotated by a hydraulic, motor or rotary table at the same 

 time it is forced down by hydraulic rams. After reaching the correct 



24 



