FLATGEO Consulting Co., Ltd.  #### List of Standards

The list of standards (ASTM, BS and TCVN) which are commonly used in... #### Holiday calendar in 2020

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July 18, 2011
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October 2, 2011
• #### Standard Penetration Test

December 12, 2011
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January 7, 2012
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February 20, 2012
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March 7, 2012
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February 27, 2014
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July 21, 2015

### Geotechnical Column

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"Symbols and definitions used in geotechnical engineering" is quoted from "Lexicon in 8 languages" (the fifth edition) published in 1981 by International Society for Soil Mechanics and Geotechnical Engineering. (If your web browser does not display properly mathematical formulae, please refer to How to change renderers in MathJax)

4. Mechanical properties of soil

a) Sampling

 Symbol Dimension Unit Measured quantity Description $$C_a$$ - % Area ratio (of a sampler) $$C_a=\frac {\left(D_2^2-D_1^2 \right)} {D_1^2}$$with $$D_1=$$ inner diameter of cutting nose; $$D_2=$$ outer diameter of cutting nose $$C_i$$ - % Inside clearance ratio (of a sampler) $$C_i=\frac {\left(D_3-D_1 \right)} {D_1}$$with $$D_1=$$ inner diameter of cutting nose; $$D_3=$$ inner diameter of container $$C_o$$ - % Outside clearance ratio (of a sampler) $$C_o=\frac {\left(D_2-D_4 \right)} {D_4}$$with $$D_2=$$ outer diameter of cutting nose; $$D_4=$$ outer diameter of barrel shaft
 (Note: concepts of $$C_a, C_i, C_o$$  are defined by Hvorslev in 1949) b) Consolidation (one dimensional)

 Symbol Dimension Unit Measured quantity Description mv M-1LT-2 (kPa)-1 Coefficient of volume change Ratio between change of volume per unit volume and corresponding change of effective normal stress:$m_v=\frac {\left(e_o-e\right)} {\left(1+e_o\right)\cdot\Delta{\sigma }^{_{´}}}$ Eoed ML-1T-2 kPa Oedometric modulus $E_{oed}=\frac {1} {m_v}$ Cc - 1 Compression index Slope of virgin compression curve in a semi-logarithmic plot "effective pressure ~ void ratio": $C_c=-\frac {\Delta e} {\quad \Delta\lg {\sigma}^{_{´}}}$ Cs - 1 Swelling index Average slope of an unload-reload cycle in a semi-logarithmic plot of effective pressure ~ void ratio: $C_s=-\frac {\Delta e} {~~ \Delta\lg {\sigma}^{_{´}}}$ C$$\alpha$$ - 1 Rate of secondary consolidation Slope of the final portion of the change of volume per unit volume ~ time curve in a semi-logarithmic plot: $C_\alpha=-\frac {\Delta e} {\; \left(1+e_o\right)\cdot\Delta\lg t}$ cv L2T-1 m²/s Coefficient of consolidation $c_v=\frac{k}{m_v\cdot \gamma_w}$ d, H L m Drainage path Thickness of layer drained on one side only, or half-thickness of layer drained on both sides Tv - 1 Time factor $T_v=\frac{t\cdot c_v}{d^2}$t being the time elapsed since application of a change in total normal stress U - 1, % Degree of consolidation Ratio of mean effective stress increase at a given time to mean final effective stress increase $$\sigma_{vo}^{´}$$ ML-1T-2 kPa Effective overburden pressure In-situ effective vertical pressure existing prior to sampling or excavation $$\sigma_{p}^{´}$$ ML-1T-2 kPa Preconsolidation pressure Maximum vertical effective past pressure

c) Shear Strength

 Symbol Dimension Unit Measured quantity Description $$\tau_f$$ ML-1T-2 kPa Shear strength Shear stress at failure in rupture plane through a given point $$c\;^{_{´}}$$ ML-1T-2 kPa Effective cohesion intercept $$\phi\;^{_{´}}$$, $$\varphi\;^{_{´}}$$ - ° Effective angle of internal friction Shear strength parameters with respect to effective stresses. Defined by the equation: $$\tau_f=c\;^{_{´}}+\sigma^{_{´}}\tan \phi^{_{´}}$$ $$c_u$$ ML-1T-2 kPa Apparent cohesion intercept $$\phi_u$$, $$\varphi_u$$ - ° Apparent angle of internal friction Shear strength parameters with respect to total stresses. Defined by the equation: $$\tau_f=c_u+\sigma\tan \phi_u$$In undrained situation, with saturated cohesive soils, $$c_u$$ is also called undrained shear strength $$c_r$$ ML-1T-2 kPa Remoulded undrained shear strength Shear strength of remoulded soil in undrained situation $$S_t$$ - 1 Sensitivity Ratio between undrained shear strength of undisturbed and of remoulded soil:$S_t=\frac{c_u}{c_r}$ $$\tau_R$$ ML-1T-2 kPa Residual shear strength Ultimate shear strength in rupture plane which a soil maintains at large displacement $$c\;^{_{´}}_R$$ ML-1T-2 kPa Residual cohesion intercept $$\phi\;^{_{´}}_R$$, $$\varphi\;^{_{´}}_R$$ - ° Residual angle of internal friction Residual shear strength parameters with respect to effective stresses, defined by the equation: $\tau_R=c\;^{_{´}}+\sigma\;^{_{´}}\tan\phi\;^{_{´}}_R$

d) In-situ Tests

Symbol Dimension Unit Measured quantity Description
$$q_c$$  ML-1T-2  kPa Static point resistance (or cone resistance) Average pressure acting on the conical point in the standard static penetration test
$$f_s$$  ML-1T-2  kPa Local side friction Average unit side friction acting on the friction sleeve in the standard static cone penetration test
$$q_d$$  ML-1T-2  kPa Dynamic point resistance Average pressure acting on the conical point in the standard dynamic penetration test ($$q_{dA}$$ and ($$q_{dB}$$ for tests of type A and B, respectively)
$$r_d$$  ML-1T-2  kPa Dynamic resistance Standardized result of the dynamic penetration test ($$r_{dA}$$ and $$r_{dB}$$ for tests of type A and B, respectively)
$$N_d$$  -  1 Number of blows per 0.2 m Standardized result of the dynamic penetration test ($$N_{dA}$$ and $$N_{dB}$$ for tests of type A and B, respectively)
$$N$$  -  1 SPT blow count Standardized result of the Standard Penetration Test
$$N_{ht}$$  -  1 Number of half-turns for 0.2 m Standardized result of the Weight Sounding Test
$$P_1$$  ML-1T-2  kPa Pressuremeter limit pressure Limit pressure defined in the standard Ménard pressuremeter test
$$E_M$$  ML-1T-2  kPa Pressuremeter modulus Conventional modulus defined in the standard Ménard pressuremeter test  Equipment for Weight Sounding Test Screw-Shaped Cone 