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Skin Friction of the Micropile Root - Graphs

The analysis of shaft resistance of the micropile root Rs depends considerably on the type of injection of micropile root. The following options of injection are considered in the program:

  • IRS: repeated selective injection of the micropile root over sleeves performed locally (Tube-á-Manchette),
  • IGU: unified global pressure injection (Looped Tube Systems).

The following graphs for the analysis of skin friction of the micropile root qs [MPa] are built in the program:

The displayed graphs consider on the horizontal axis the limit pressure pLM determined from the pressuremeter tests (PMT). In case of SPT tests, the same graphs are used, but the limit pressure pLM [MPa] is then determined as the n-multiple of the number of blows N for the interval of penetration depth d = 0.3 m, i.e. SPT [N/0.3 m]. For individual types of soils the values of limit pressure pLM according to Menard are as follows:

  • sand, gravel, silt and weak rock: pLM = SPT / 20,
  • clays: pLM = SPT / 15.

For example, for the sandy soil and the value of the multiple of number of blows SPT = 120 the limit pressure is given by pLM = SPT / 20 = 120 / 20 = 6.0 MPa.

Next, for example, for the clayey soil and the value of a multiple number of blows SPT = 30 the limit pressure is provided by pLM = SPT / 15 = 30/15 = 2.0 MPa.

The vertical axis provides the value of skin friction of the micropile root qs depending on the value of limit pressure pLM and the applied type of injection (IRS or IGU, respectively).

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