Prefabricated, modular hydropower foundation system for soil conditions

Abstract

A foundation system for modular hydropower systems and methods for constructing same. The foundation system is compatible with soils, particularly soils that are relatively loose or compressible, and thereby advantageous for the widespread implementation of low head modular hydropower systems. The foundation system includes pipe piles; sheet piles configured to be arranged transverse to the pipe piles; pile caps configured to be seated on top of the plurality of pipe piles; and a beam base slab configured to be securely positioned on top of the pile caps. A kit for the foundation system is also disclosed.

What is claimed is: 
     
         1 . A method for constructing and installing a modular foundation system, comprising the steps of:
 (a) installing a plurality of pipe piles advancing from a first abutment into a waterway;   (b) installing upstream and downstream sheet pile rows between two or more of the plurality of pipe piles;   (c) seating a plurality of pre-cast concrete pile caps;   (d) placing a temporary construction matting to span between two rows of the plurality of pile caps to serve as an access staging platform for a crane;   (e) advancing the crane to an end of the temporary access staging platform;   (f) repeating steps (a)-(e) until all of the piles and pile caps have been installed across half of a width of a dam axis;   (g) installing longitudinal pre-cast bottom beams of a base slab;   (h) Installing temporary upstream and downstream water control plates for the half of the dam width to allow for additional work to be completed in the dry and maintain flow through the other half of the waterway;   (i) installing top pre-cast beams for the base slab;   (j) installing tie-downs, as needed;   (k) erecting modules on the completed half of the foundation; and   (l) removing the water control plates for the completed half of the foundation.   
     
     
         2 . The method of  claim 1 , further comprising the steps of (m) installing a second plurality of pipe piles advancing from a second abutment into the waterway; and
 (n) repeating steps (b)-(l) with in connection with the second abutment, to meet the completed construction in mid-stream.   
     
     
         3 . The method of  claim 2 , further comprising the step of preparing the first and second abutments, the preparing step being performed before step (a). 
     
     
         4 . The method of  claim 1 , wherein step (a) is performed through an associated water column using a movable template to maintain positioning of the pipe piles. 
     
     
         5 . A foundation system for modular hydropower systems comprising:
 a plurality of pipe piles;   a plurality of sheet piles configured to be arranged transverse to the pipe piles;   a plurality of pile caps configured to be seated on top of the plurality of pipe piles; and   a beam base slab configured to be securely positioned on top of the pile caps.   
     
     
         6 . The foundation system of  claim 5 , wherein the beam base slab includes a first plurality of beams arranged in a first row, and a second row of beams arranged in a second row layered on top of the first row at a ninety-degree angle thereto. 
     
     
         7 . The foundation system of  claim 6 , wherein the beams of the first plurality of beams are tied together. 
     
     
         8 . The foundation system of  claim 6 , wherein the first and second pluralities of beams are secured together by post-tensioned tie rods to create monolithic action between the first and second pluralities of beams, whereby the section modulus of the beam base slab is increased. 
     
     
         9 . The foundation system of  claim 6 , wherein the beams of the first plurality of beams contain embedded HSS members to maximize tension capacity at top and bottom chords of the first beams. 
     
     
         10 . The foundation system of  claim 5 , wherein the pile caps are formed from pre-cast concrete. 
     
     
         11 . The foundation system of  claim 5 , wherein the pile caps are seated by gravity, by mechanical connections or by a combination of gravity and mechanical connections. 
     
     
         12 . The foundation system of  claim 5 , wherein the pile caps have a length that spans across two piles in a transverse direction. 
     
     
         13 . The foundation system of  claim 12 , wherein the pile cap length is 12 feet. 
     
     
         14 . The foundation system of  claim 5 , wherein the pile caps are staggered to more evenly distribute forces into the piles. 
     
     
         15 . The foundation system of  claim 5 , wherein the pipe piles are formed from steel. 
     
     
         16 . The foundation system of  claim 5 , wherein the sheet piles are formed from steel. 
     
     
         17 . The foundation system of  claim 5 , wherein the plurality of pipe piles includes upstream pipe piles and downstream pipe piles. 
     
     
         18 . The foundation system of  claim 5 , wherein one of the plurality of sheet piles is arranged between two of the plurality of pipe piles. 
     
     
         19 . The foundation system of  claim 5 , further including at least one tie-down securable to the base slab. 
     
     
         20 . A kit for constructing a foundation system for modular hydropower systems; comprising:
 a plurality of pipe piles;   a plurality of sheet piles configured to be arranged between the pipe piles;   a plurality of pile caps configured to be seated on top of the plurality of pipe piles; and   a beam base slab configured to be securely positioned on top of the pile caps, the beam base slab including a first plurality of beams arranged in a first row, and a second row of beams arranged in a second row layered on top of the first row.