Answer Happy

a) What is the maximum SPT-N value commonly considered as
stiffsoil?
b) For SPT-N values more than 50, computed the equivalent value
based on ratio of (50/N × 300).
c) Compute the conversion from SPT-N value to shear wave
velocity (SWV) of each layer of soil, Vsi using the Imai and
Tonouchi (1982) empirical equation for all soil type, Vsi= 97 N
0.314 .
d) Compute the average SWV of the borehole (refer to Figure 1
for the formula of Vs).
e) Compute the site natural period (TS) using the formula of TS
in Figure 1.
f) Recommend the ground type according to the classification
scheme in Figure 1 (i.e. Model B in the Malaysia EC8 NA, 2017).
g) Convert the RSA into RSD and Plot the ADRS diagram.
h) Compare your answers in 1(e) and 1(g) with program MY1 on
quakeadice.org.
1. Soil natural period and selection of Model B from Malaysia EC8 NA (2017): Table 1 shows an example of borehole log record at a site in Johor Malaysia. Table 1: A borehole log record at a site in Johor Malaysia Depth di Descriptions (m) (m) 0.0 pale to light brown sandy SILT (D1) 0 1.5 soft pale to light brown clayey SILT (P1/D2) 1.5 3.0 1.5 very soft light to grey silty CLAY with sand (P2/D3) very soft to soft light grey silty SAND (P3/D4) 4.5 1.5 6.0 firm pale to light grey sandy CLAY (P4/D5) UD2 at 6.5m 1.5 7.5 firm to stiff pale to light grey sandy CLAY (P5/D6) 1.5 9.0 1.5 firm light grey and pale brown silty CLAY (P6/D7) UD3 at 9.5m stiff pale to light brown silty CLAY (P7/D8) 10.5 1.5 12.0 1.5 stiff pale to light grey silty CLAY with fine sand (P8/D9) ditto (P9/D10) 13.5 1.5 15.0 stiff pale to light grey silty CLAY with sand (P10/D11) 1.5 1.5 18.0 stiff to very stiff pale to light grey silty CLAY with sand (P11/D12) very stiff pale to light grey silty CLAY with fine sand (P12/D13) very stiff pale to light grey sandy CLAY (P13/D14) 1.5 19.5 1.5 21.0 ditto (P14/D15) 1.5 22.5 hard pale to light grey sandy CLAY (P15/D16) 1.5 24.0 hard light to grey sandy CLAY (P16/D17) 1.5 25.5 ditto (P17/D18) 1.5 27.0 ditto (P18/D19) 1.5 28.5 1.5 very dense light to grey silty SAND (P19/D20) hard light to grey sandy CLAY (P20/D21) 30.0 1.5 31.5 ditto (P21/D22) 1.5 33.0 hard pale to light grey sandy CLAY (P22/D23) 1.5 34.5 hard light to medium grey sandy CLAY (P23/D24) 1.5 [5 marks] SPT-N 3 2 2 7 8 9 10 12 14 12 15 18 25 20 32 35 38 40 55 125 140 135 110
Table A.1. Ground classification scheme in accordance to site natural period for soil deposit exceeding 30 m in depth Ground Description and range of site natural period, Ts (s)* type A Rock site, or a site with very thin sediments and Is < 0.15 s B A site not classified as ground type A, C, D or E A site with sediments of more than 30 m deep to bedrock and Ts = 0.5 s to 0.7 s D A site with sediments of more than 30 m deep to bedrock and Ts = 0.7 s to 1.0 s E A site with sediments of more than 30 m deep to bedrock and Ts => 1.0 s, or deposits consisting of at least 10 m thick of clays/silts with a high plasticity index (Pl> 50) NOTE. A soil site is characterised by its small-strain site natural period (Ts) of the soil layer down to the depth of much stiffer sediments or bedrock. For soil sediments of more than 30 m deep to bedrock, Is can be estimated using the formula: H₂ T₁ = 4 X H₂ V₂ The values of the site natural period (Ts), small-strain shear modulus or shear wave velocity (SWV, V's) of soils can be measured by various geotechnical or geophysical testing techniques. Sedimentary layers with SPT-N value greater than 100 can be omitted in the computations of site natural period and weighted average, SWV. Generally, two boreholes for a block of low-rise building are sufficient. Spacing of boreholes for multi- storey buildings should be 15 m to 45 m. More boreholes are necessary for problematic and erratic soil formation. The arithmetic mean of the site natural period Is shall be adopted for site classification. Figure 1: Ground classification scheme with site period parameterisation according to the Malaysia EC8 NA (2017)