When the shallow earths are not powerful enough to support the loads from the construction deep foundations are needed. The loads are resisted through point bearing and skin friction. Conduit can be driven open-ended or closed-ended, with points or plates. The pipes can subsequently be filled with concrete to add strength to the pile if driven with plates. Normally the money spent on plates and concrete would be better spent on a bigger, thicker heap.
The arrangement of the top stone layer and the place of the stone surface is ascertained with soundings when point bearing pile foundations are used. The place and shape of the rock surface is notably investigated, when cohesive layers extend to the stone surface, when there’s a loose coarse grained earth or moraine layer on an inclined rock surface and when the dense coarse grained earth or moraine layer on an inclined rock surface is thin. If the coarse grained ground or moraine layer is sufficiently dense and thick, in order that the adequate geotechnical bearing capacity is reached by piles without penetration into the rock, the soundings can be completed in the tough base layer.
In general the place of the stone surface must be discovered with percussion drilling. To define density and the stack penetration of the ground layers dynamic probing has to be carried out. When point bearing heaps which go to the stone are used, the location of the rock surface is consistently decided with percussion drilling at each pile group. In specific cases it is essential to clarify the upper rock structure with rock core borings.
When friction piles are used, the density of the layers and the borders between the earth layers, are determined for the layers that were penetrated and notably for the heap bearing layers. Soil survey is largely carried out using standard penetration tests, dynamic probing or cone penetration tests. During the choice of studying operations and investigation methods it is crucial to find and localize potential cohesive soil layers between cohesionless soil layers.
In order to discover the shaft friction it is suggested that the strength parameters of the ground are investigated using, for instance, triaxial testing.
A land stopper can develop at the stage of the open-ended pipe pile during pile driving. Soil samples must be chosen from the plugging ground layer to determine at the minimum the grain size distribution, but rather also the strength parameters if the ground plug is exploited in the design of the geotechnical bearing capacity of the heap.
Tension on piles
Where stacks are used, that are forever or repeatedly subjected to bigger tension loads than the powerful weight of the heap, the friction and adhesion between soil layers and the pile shaft has to be determinable from the basis of the soil survey. Long term tension can be enabled only for piles in coarse or moraine layers. For this goal the soil survey corresponding to the survey demanded for friction piles is needed. Transient tension can be enabled also in cohesive soil layers. For this purpose the vane are essential to ascertain the adhesion of the pile shaft.