Derived Parameters

Standard Parameters

The following table presents the derived parameters. These calculations are hard coded, and are calculated before the Formula Tool.

DGD Field NameCaptionSymbolUnitDescription
Penetration_Rate


Rate calculated based on Time_Elapsed and Depth
Bulk_Unit_WeightBulk Unit Weight

γ_b

kN⁄m^3

Bulk unit weight, γ_b

In_Situ_Pore_PressureIn Situ u

u_o

kPa

In situ pore pressure, u_o, refer to section Groundwater and Over water Testing for a full explanation.

Excess_Pore_PressureDelta u

\Delta u

kPa

Excess pore pressure, ∆u =u_2 - u_o

Normalised_Excess_Pore_PressureNormalised Delta u

Normalised \Delta u


Normalised excess pore pressure, normalised ∆u =\frac{ u_2 - u_o}{\sigma'_{vo}}

Slope_IndicatorInclination

\alpha

deg

Non-directional inclinometer measured value, or calculated from  \alpha={\sqrt{\beta_{1}^2+\beta_{2}^2}}

Total_StressTotal Stress

σ_{vo}

kPa

In situ total vertical stress, σ_{vo}=\sum^{n}_{i=1} \gamma_{bi} \Delta z_i

Effective_StressEffective Stress

σ'_{vo}

kPa

In situ effective vertical stress, \sigma'_{vo}=σ_{vo}-u_o

Total_Cone_Resistanceqt

q_t

MPa

Total cone resistance,
q_t = q_c + u_2 (1 -a);
or if the instrument is zeroed at the bottom of the borehole (downhole) q_t = q_c^* + u_2 (1 -a)+\gamma_w \cdot d

Total_Cone_Resistance_Moving_AverageMoving Average qt

MPa

Moving average qt over distance defined on CPT_PROJECT_PARAMETERS
Total_Cone_Resistance_Moving_Average_IncMoving Average qt Included

MPa

Moving average qt that are not excluded over distance defined on CPT_PROJECT_PARAMETERS
Net_Cone_Resistanceqn

q_n

MPa

Net cone resistance,
q_n = q_t - \sigma_{v0}

Corrected_Sleeve_Frictionft

f_t

kPa

Sleeve friction corrected for pore pressure effects,

f_t = f_s - \frac{(u_2 \cdot A_{sb} - u_3 \cdot A_{st})}{A_s}

Friction_RatioRf

R_f

%

Friction ratio: R_f = \frac{f_t}{q_t}\cdot 100, R_f = \frac{f_s}{q_t}\cdot 100, or R_f = \frac{f_s}{q_c}\cdot 100
See section Soil Behaviour Type.

Normalised_Friction_RatioFr

F_r

%

Normalised friction ratio,
F_r = \frac{f_s}{(q_t-\sigma_{v0})}
If q_t is not found, and if Calc_Qt_Fr_based_on_qc on CPT_PROJECT_PARAMETERS is set to true, then q_c is used in place of q_t.

Normalised_Cone_ResistanceQt

Q_t

-

Normalised cone resistance, Q_t = \frac{(q_t-\sigma_{v0})}{\sigma'_{v0}}
If q_t is not found, and if Calc_Qt_Fr_based_on_qc on CPT_PROJECT_PARAMETERS is set to true, then q_c is used in place of q_t.

Stress_Normalised_Cone_Resistanceqt1

q_{t1}

-

Stress normalised cone resistance (Kulhawy and Mayne 1990, Jamiolkowski et al 2001), q_{t1}=\frac{q_t}{\sqrt{\sigma'_{v0}\cdot\sigma_{atm}}}

Pore_Pressure_RatioBq

B_q

-

Pore pressure ratio, B_q= \frac{\Delta u}{(q_t-\sigma_{v0})}

Differential_Pore_Pressure_RatioDPPR

DPPR

-

Differential pore pressure ratio, DPRR= \frac{\Delta u}{q_t}

Dimensionless_Penetration_ResistanceQt(1-Bq)+1

Q_t(1-B_q )+1

- Dimensionless penetration resistance

Begemann Mechanical Cone Calculations

In case of using a Begemann mechanical subtraction cone, the corrected values for q_c and f_s are calculated from input data cone readings 1 and 2 as:

q_c = M_1 \cdot \frac{ A_p}{A_c} +W_1+W_2 \cdot n\\ \ \\ \text{Or if one of }M_1, A_p, A_c, W_1 \text{ or }W_2 \text{ is NULL:} \quad q_c = M_1
f_s = (M_{2\text{, row i+1}}-M_{1\text{, row i+1}} ) \cdot A_p/A_s
TF = \sum f_s \cdot (z_i - z_{i-1})


Where:

     M_1 is the mechanical cone reading 1 and is taken from Mechanical_Reading_1 field, for f_s values from the next row are used

     M_2 is the mechanical cone reading 2 and is taken from Mechanical_Reading_2 field, for f_s values from the next row are used

     A_p is the area of plunger and is taken from Area_Plunger field on CPT_CONE_INFORMATION

     A_c is the projected area of the cone and is taken from Area_Cone field on CPT_CONE_INFORMATION

     W_1 is the mass of cone and is taken from Mass_Cone field on CPT_CONE_INFORMATION

     W_2 is the mass of cone inner rod and is taken from Mass_Inner_Rod field on CPT_CONE_INFORMATION

     n is the number of rods used, calculated from dividing Depth by Length_Inner_Rod on CPT_CONE_INFORMATION, rounded up to nearest whole number plus one if the top of the rod is at the ground surface

     A_s is the area of sleeve and is taken from Area_Friction_Casing field on CPT_CONE_INFORMATION

     TF is the Total Sleeve Friction Resistance

Friction Ratio Calculation Method

The field Friction_Ratio_Calculation_Method on CPT_PROJECT_PARAMETERS defines the method of calculation. The options are:

  • qt or qc on same row as fs: All data is taken form the same row, this is the default
  • Average qt or qc over sleeve: Uses average (arithmetic mean) qt or qc over range of sleeve
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