Mineral precipitation methods

Abstract

The present invention provides methods for mineral precipitation of porous particulate starting materials using isolated urease.

What is claimed is: 
     
         1 . A mineral precipitation method, comprising:
 combining a saturated, porous, particulate starting material with   (a) isolated urease;   (b) urea; and   (c) a source of divalent cations;   wherein (a), (b), (and (c) are provided in amounts effective and the combining is carried out under conditions suitable to cause carbonate precipitation of the starting material.   
     
     
         2 . The method of  claim 1 , further comprising combining the starting material with powdered milk to act as a stabilizer. 
     
     
         3 . The method of  claim 1 , wherein the method is used for one or more of improving bearing capacity of foundations; reducing settlement potential of foundations or embankments; stabilizing slopes; reducing the potential for earthquake-induced liquefaction; mitigating the potential for damaging ground displacements subsequent to earthquake-induced liquefaction; increasing lateral resistance of foundations; enhancing stability of slopes or embankments; reducing lateral earth pressures on retaining walls; increasing passive resistance of retaining walls; increasing capacity of ground anchors or soil nails; increasing the side resistance and tip resistance of deep foundations; facilitating tunneling in running or flowing ground; stabilizing excavations bottoms; soil erosion control; or groundwater control. 
     
     
         4 . The method of  claim 1 , wherein the starting material comprises one or more of sand, silt, clay, sawdust, igneous rocks, metamorphic rocks, gravel, fractured crystalline rocks, cracked concrete, or sedimentary rocks. 
     
     
         5 . The method of  claim 1 , wherein the source of divalent cations comprises a source of divalent calcium ions. 
     
     
         6 . The method of  claim 1 , wherein the combining step is carried out more than once. 
     
     
         7 . The method of  claim 1 , wherein the combining comprises:
 (i) mixing the urease with the starting material; and   (ii) injecting into the starting material, under pressure and via an injection tube, a solution comprising the urea and the source of divalent cations.   
     
     
         8 . The method of  claim 7 , wherein the injecting is carried out two or more times. 
     
     
         9 . The method of  claim 7 , wherein the urease is mixed with starting material in only a portion of the starting material prior to the injecting. 
     
     
         10 . The method of  claim 1 , wherein the method further comprises introducing a clay slurry into the starting material prior to or concurrent with combining the starting material with the isolated urease, the urea, and the source of divalent cations. 
     
     
         11 . The method of  claim 1 , wherein the saturated starting material comprises a column of the saturated starting material. 
     
     
         12 . The method of  claim 1 , wherein the combining is conducted underneath or adjacent to an existing structure that is sensitive to ground settlement or heave. 
     
     
         13 . The method of  claim 12 , wherein the carbonate precipitation does not cause ground settlement or heave affecting the existing structure.