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Modulus of Subsoil Reaction According to Chinese standards

The calculation of modulus of subsoil reaction according to Chinese standards is based on the JGJ 120-2012 standard (Technical specification for retaining and protection of building foundation excavations) for "m" method.

For "m" method, the modulus of subsoil reaction kh is given by the following formula:

where:

m

-

proportional coefficient of modulus of subsoil reaction [kN/m4]

z

-

depth of the calculation point from the original ground [m]

h

-

depth of the calculation point from the ditch bottom at current stage of construction [m]

From previous formula it’s obvious that calculation of modulus kh is linear with depth of point during the analysis.

Proportional coefficient m should be determined from pile test with horizontal load. If there are no test data, Chinese standard JGJ 120-2012 suggest an empirical formula to estimate this coefficient:

where:

c

-

cohesion (shear strength) of soil [kPa]

φ

-

angle of internal friction of soil [°]

vb

-

horizontal displacement of sheeting structure at the ditch bottom [mm]; when the displacement is smaller than 10 mm, then vb = 10 mm

Other methods ("c" method and "k" method) are not published in JGJ 120-2012 standard, but they are based on practical experience and they are used in China profusely. Then the modulus of subsoil reaction kh is given by the following formula:

If exponent n = 0,5, it's "c" method and then a = c (kN/m3.5).

If exponent n = 0, it's "k" method and then, a = K (kN/m3).

It’s obvious that for "m" method, n = 1.

Literature:

JGJ 120-2012 (Technical specification for retaining and protection of building foundation excavations).