Foundation for a Wind Turbine Utilizing a Slurry of Low Viscosity Grout

Abstract

A self-leveling grout provides a level surface for the disposition of a wind turbine base. The self-leveling grout is placed within the foundation grout trough as an initial slurry having a viscosity at ambient temperature approximately the same as the viscosity of known grout slurries utilized in turbine foundations. After placement in the grout trough, elevated temperature is applied to the grout slurry, which lowers the viscosity of the slurry such that the slurry becomes self-leveling and the top surface assumes a nearly perfectly level surface. Additional elevated temperature is applied which initiates the curing of the grout to the required compressive strength for supporting the turbine tower.

1 . A method for using low-viscosity grout in the installation of a wind turbine foundation, the method comprising the steps of:
 providing a plurality of anchor bolts within a generally vertical excavation;   cementing the anchor bolts within the excavation wherein a top surface of the cement comprises a grout trough;   introducing a slurry of low-viscosity grout into the grout trough, the slurry of low-viscosity grout comprising the rheological properties of having a first viscosity at ambient temperature and a second viscosity at a first elevated temperature, wherein the first viscosity is higher than the second viscosity, and the grout self-levels to a level surface at the first elevated temperature;   allowing the low-viscosity grout to cure to an acceptable compressive strength; and   securing a base flange to the anchor bolts.   
     
     
         2 . The method according to  claim 1  wherein each of said anchor bolts is disposed within a sleeve extending substantially along the length of the anchor bolt, the method further comprising the step of obstructing an opening between an interior wall of the sleeve and a surface of the anchor bolt such that the low-viscosity grout cannot enter into a space between the interior wall of the sleeve and the surface of the anchor bolt. 
     
     
         3 . The method according to  claim 2  wherein the opening between an interior wall of the sleeve and a surface of the anchor bolt is obstructed by providing a swaged upper end of said sleeve conforming substantially to a surface of said anchor bolt. 
     
     
         4 . The method according to  claim 1  wherein the slurry of low viscosity grout comprises an epoxy, and further comprising the steps of mixing a base component of said grout and a catalyst component of said grout prior to introducing the slurry of low viscosity grout into the trough. 
     
     
         5 . The method according to  claim 1  further comprising the step of heating the slurry of the low viscosity grout further, such that the slurry hardens to a grout having an acceptable compressive strength to support the weight of the base flange in a level position. 
     
     
         6 . The method according to  claim 5  further comprising the step of allowing the grout to cool prior to securing the base flange. 
     
     
         7 . The method according to  claim 1  wherein heat is applied to the slurry of low-viscosity grout by a cover structure comprising heating elements. 
     
     
         8 . The method of  claim 7  wherein the cover structure comprises means for evenly distributing heat about the slurry of low viscosity grout. 
     
     
         9 . The method of  claim 7  wherein the cover structure comprises a plurality of arc length sections. 
     
     
         10 . A foundation for supporting a wind turbine comprising:
 a plurality of anchor bolts disposed within a vertical excavation;   a cement disposed within the vertical excavation such that a substantial portion of a length of each of said plurality of anchor bolts is embedded within the cement, the cement having an upper surface defining a trough; and   a grout disposed within said trough, the grout initially introduced into the trough as a slurry having the rheological properties of having a first viscosity at ambient temperature and a second viscosity at a first elevated temperature, wherein the first viscosity is higher than the second viscosity, and the grout slurry is self-leveling to a level surface at the first elevated temperature.   
     
     
         11 . The foundation according to  claim 10  further comprising a sleeve extending substantially along the length of an anchor bolt, the sleeve preventing contact between the anchor bolt and the cement, the sleeve comprising a swaged upper end such that the upper end of the sleeve conforms substantially to a surface of the anchor bolt. 
     
     
         12 . The foundation according to  claim 10  wherein the trough is an annular trough. 
     
     
         13 . A method of constructing a foundation for a wind turbine tower, comprising the following steps:
 providing a plurality of anchor bolt packages within a generally vertical excavation, wherein each anchor bolt package comprises an anchor bolt and a polypropylene sheath extending along a substantial portion of the exterior of the anchor bolt;   cementing the anchor bolts within the excavation wherein a top surface of the cement comprises a grout trough with upwardly extending ends of the anchor bolt packages extending above the grout trough;   introducing a low-viscosity grout slurry into the grout trough, the low-viscosity grout slurry comprising the rheological properties of having a first viscosity at ambient temperature and a second viscosity at a first elevated temperature, wherein the first viscosity is higher than the second viscosity, and the grout is self-leveling to a level surface at the first elevated temperature;   allowing the low-viscosity grout slurry to cure to an acceptable compressive strength, the grout slurry curing to a hardened grout having a perfectly level top surface;   lowering a base flange onto the level top surface of the hardended grout; and   securing a base flange to the upwardly extending ends of the anchor bolt packages.   
     
     
         14 . The method according to  claim 13  wherein heat is applied to the slurry of low-viscosity grout by a cover structure comprising heating elements. 
     
     
         15 . The method of  claim 14  wherein the cover structure comprises means for evenly distributing heat about the slurry of low viscosity grout. 
     
     
         16 . The method of  claim 14  wherein the cover structure comprises a plurality of arc length sections. 
     
     
         17 . The method of  claim 14  wherein the cover structure comprises control means for adjusting the temperature within the cover structure.