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#### List of Standards

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

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Date Number of days off 2020  New Year's...

#### Standard Penetration Test

Standard penetration test (SPT) is one of the most common in situ testing...

#### Precision or Accuracy ???

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• #### List of Standards

July 18, 2011
• #### Holiday calendar in 2021

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

December 12, 2011
• #### Precision or Accuracy ???

January 7, 2012
• #### Bulk Density

February 20, 2012
• #### Compaction Test

March 7, 2012
• #### Warning on Webpage Content Stealing

February 27, 2014
• #### Datalogger for Oedometers

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.

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