BRACING OF FOUNDATION PITS - MICRORIDER BRACING

Carrying out shotcretes

Microrider walls (also called Genova walls) represent an alternative to the most commonly used type of rider bracing. They can be used in confined spaces without a possibility of handling bigger building machinery and in places where it is necessary to design a sheeting construction of a minimal thickness. They are most often applied in cases of built-up areas in towns, where it is necessary to sheet a deep foundation pit so that the serviceable area of a built-up space was as large as possible for the purposes of a new building. Microrider walls consist of the following components:

  • » microriders – these are, in principle, non-grouted micropiles with reinforcement of thick wall pipes or with reinforcement made of I, H rolled sections, while the diameter of holes in filled with cement suspension or mortar ranges between 130–300 mm and the axial span falls between 400 and 800 mm.
  • » fillings between microriders that are usually made of shotcrete with a reinforcement mesh, less often made of pieces of steel sheeting boards Union, rarely planks or prisms.
  • » strap anchors – most commonly steel, pre-set, consisting of sheet piles, a pair of U-sections, etc.
  • » anchors, which are mainly temporary, bar or strand.

Drilling anchors securing the micropile sheeting stability; the New Connection in PragueWith respect to the dimension of individual components– especially microriders – it is obvious that this construction is relatively soft and mostly needs to be anchored or strutted at several levels. Because of the fact that basement walls of newly built constructions are usually provided with insulation, it is required that the surface of microrider walls was smooth and created a direct base for insulation. This requirement is, however, difficult to meet, as it is necessary to transfer anchoring, or strutting to microriders over strap anchors protruding over them. It is also needed to arrange the strap anchors from the point of view of height so that it corresponded not only with the static objective, but also with the position of future ceilings and it was possible to remove them without problems in the course of gradual building of the basement. Microrider bracing is often combined with other technologies of special foundation works, especially with jet grouting columns and standard or sealing grouting.

Micropile sheeting scheme, view and cut

Micropile sheeting scheme, view and cut

Micropile sheeting scheme, lay-out
2a) micropiles
2b) anchors
2c) strap anchors

Micropile sheeting scheme, lay-out

Carrying out vertical elements of the on-coming micropile sheetingView of a partly excavated micropile wallMicropile sheeting detail after excavation