Abstract:
Specialised grouting methods were used to remediate a sheet pile retaining wall in zone of high turbulence, immediately downstream of the Taupo Control Gates on the Waikato River. Wagstaff Piling NZ, together with McConnell Dowell, developed the remedial work, involving a rapid gelling grout. Versions of this approach which has been progressively developed over the last 12 years, has been successfully used on previous notable projects, although always with variations of the theme. The project required a rapid gelling grout to hold the grout in place, and prevent migration into the river, through highly permeable, voided and chaotic material behind the sheet pile wall. The grout mix design incorporated a Part A and Part B mix where sodium silicate was the key activator to a cementitious grout, with variable gel times controlled by the injection system to suit the down hole conditions encountered. The variable control allowed the grout to effectively fill voided material while confining it to targeted areas, all in close proximity to the turbulent river. Finally, a series of tube-a-manchette (TAMs) were installed for post grouting. The post grouting of the TAMs would be an important verification stage. This project was an innovative solution in extreme conditions and is an example of a customised approach to drilling and grouting, used to resolve a difficult problem. Hybrid techniques such as this are not textbook solutions, involving combining variable techniques, although showing that with lateral thinking and drawing on experience, the most challenging conditions can be overcome.Specialised grouting methods were used to remediate a sheet pile retaining wall in zone of high turbulence, immediately downstream of the Taupo Control Gates on the Waikato River. Wagstaff Piling NZ, together with McConnell Dowell, developed the remedial work, involving a rapid gelling grout. Versions of this approach which has been progressively developed over the last 12 years, has been successfully used on previous notable projects, although always with variations of the theme. The project required a rapid gelling grout to hold the grout in place, and prevent migration into the river, through highly permeable, voided and chaotic material behind the sheet pile wall. The grout mix design incorporated a Part A and Part B mix where sodium silicate was the key activator to a cementitious grout, with variable gel times controlled by the injection system to suit the down hole conditions encountered. The variable control allowed the grout to effectively fill voided material while confining it to targeted areas, all in close proximity to the turbulent river. Finally, a series of tube-a-manchette (TAMs) were installed for post grouting. The post grouting of the TAMs would be an important verification stage. This project was an innovative solution in extreme conditions and is an example of a customised approach to drilling and grouting, used to resolve a difficult problem. Hybrid techniques such as this are not textbook solutions, involving combining variable techniques, although showing that with lateral thinking and drawing on experience, the most challenging conditions can be overcome.