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Skin Friction of the Micropile Root - Graphs

The analysis of shaft resistance of the micropile root R_s 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 q_s [MPa] are built in the program:

The displayed graphs consider on the horizontal axis the limit pressure p_LM determined from the pressuremeter tests (PMT). In case of SPT tests, the same graphs are used, but the limit pressure p_LM [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 p_LM according to Menard are as follows:

• sand, gravel, silt and weak rock: p_LM = SPT / 20,
• clays: p_LM = 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 p_LM = 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 p_LM = SPT / 15 = 30/15 = 2.0 MPa.

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