Cohesive soils

groundhog.siteinvestigation.correlations.cohesive.compressionindex_watercontent_koppula(water_content, cc_cr_ratio=7.5, **kwargs)

Based on an evaluation of the compression index of clays and eight other soil mechanics parameters, Koppula (1981) concluded that the best fit was obtain using a direct relation with natural water content.

The recompression index is also calculated using a user-defined ratio of \(C_c\) and \(C_r\). This ratio is generally between 5 and 10.

Parameters:

• water_content – In-situ natural water content of the clay (\(w_n\)) [\(-\)] - Suggested range: 0.0 <= water_content <= 4.0

• cc_cr_ratio – Ratio of compression index and recompression index (\(C_r / C_c\)) [\(-\)] - Suggested range: 5.0 <= cc_cr_ratio <= 10.0 (optional, default= 7.5)

\[ \begin{align}\begin{aligned}C_c = w_n\\C_c / C_r = 5 \ \text{to} \ 10\end{aligned}\end{align} \]

Returns:

Dictionary with the following keys:

• ’Cc [-]’: Compression index (\(C_c\)) [\(-\)]

• ’Cr [-]’: Recompression index (\(C_r\)) [\(-\)]

Reference - Koppula SD (1981) Statistical evaluation of compression index. Geotech Test J ASTM 4(2):68–73

groundhog.siteinvestigation.correlations.cohesive.cv_liquidlimit_usnavy(liquid_limit, trend='NC', **kwargs)

Calculates an estimate of the coefficient of consolidation based on the liquid limit of a clay. Three trends are available; an upper bound trend for remoulded clays, a trend for normally consolidated and a lower bound trend for undisturbed overconsolidated clay. Note that sample disturbance can lead to a reduced coefficient of consolidation.

Parameters:

• liquid_limit – Liquid limit of the clay (\(LL\)) [\(pct\)] - Suggested range: 20.0 <= liquid_limit <= 160.0

• trend – Choice of trend, choose between trends for remoulded, NC and OC clay (optional, default= ‘NC’) - Options: (‘Remoulded’, ‘NC’, ‘OC’)

Returns:

Dictionary with the following keys:

• ’cv [m2/yr]’: Coefficient of consolidation (\(c_v\)) [\(m2/yr\)]

Proposed relation between coefficient of consolidation and liquid limit

Reference - U.S. Navy (1982) Soil mechanics – design manual 7.1, Department of the Navy, Naval Facilities Engineering Command, U.S. Government Printing Office, Washington, DC

groundhog.siteinvestigation.correlations.cohesive.frictionangle_plasticityindex(plasticity_index, **kwargs)

Based on a dataset of soft to stiff clays, a correlation between plasticity index and drained friction angle of clay is proposed. It should be noted that the friction angle of overconsolidated depends strongly on the in-situ condition. If the overconsolidated is fissured, the available shearing resistance will be lower than the value resulting from the correlation.

Parameters:

plasticity_index – Plasticity index of the clay as determined from Atterberg limit tests (\(PI\)) [\(pct\)] - Suggested range: 5.0 <= plasticity_index <= 1000.0

Returns:

Dictionary with the following keys:

• ’Effective friction angle [deg]’: Drained friction angle of the clay (\(\varphi^{\prime}\)) [\(deg\)]

Dataset used for the correlation

Reference - Terzaghi, K., Peck, R. B., & Mesri, G. (1996). Soil mechanics in engineering practice. John Wiley & Sons.

groundhog.siteinvestigation.correlations.cohesive.gmax_plasticityocr_andersen(pi, ocr, sigma_vo_eff, atmospheric_pressure=100.0, coefficient_1=30.0, coefficient_2=75.0, coefficient_3=0.03, coefficient_4=0.5, coefficient_5=0.9, **kwargs)

Calculates the small-strain shear modulus for cohesive soils based on plasticity index, effective overburden pressure and OCR. The proposed relation is calibrated on a number of shear wave velocity tests on clay samples with different plasticity index and OCR.

Parameters:

• pi – Plasticity index (difference between liquid limit and plastic limit) (\(PI\)) [\(pct\)] - Suggested range: 0.0 <= PI <= 160.0

• ocr – Overconsolidation ratio of the clay (\(OCR\)) [\(-\)] - Suggested range: 1.0 <= OCR <= 40.0

• sigma_vo_eff – Vertical effective stress (\(\sigma_{vo}^{\prime}\)) [\(kPa\)] - Suggested range: 0.0 <= sigma_vo_eff <= 1000.0

• atmospheric_pressure – Atmospheric pressure (\(P_a\)) [\(kPa\)] - Suggested range: 90.0 <= atmospheric_pressure <= 110.0 (optional, default= 100.0)

• coefficient_1 – First calibration coefficient (:math:``) [\(-\)] (optional, default= 30.0)

• coefficient_2 – Second calibration coefficient (:math:``) [\(-\)] (optional, default= 75.0)

• coefficient_3 – Third calibration coefficient (:math:``) [\(-\)] (optional, default= 0.03)

• coefficient_4 – Fourth calibration coefficient (exponent for OCR) (:math:``) [\(-\)] (optional, default= 0.5)

• coefficient_5 – Fifth calibration coefficient (exponent for sigma_ref) (:math:``) [\(-\)] (optional, default= 0.9)

\[ \begin{align}\begin{aligned}\frac{G_{max}}{\sigma_{ref}^{\prime}} = \left( 30 + \frac{75}{\frac{I_p}{100} + 0.03} \right) \cdot OCR^{0.5}\\\sigma_{ref}^{\prime} = P_a \cdot \left( \sigma_{0}^{\prime} / P_a \right)^{0.9}\end{aligned}\end{align} \]

Returns:

Dictionary with the following keys:

• ’sigma_0_ref [kPa]’: Reference stress (\(\sigma_{ref}^{\prime}\)) [\(kPa\)]

• ’Gmax [kPa]’: Small-strain shear modulus (\(G_{max}\)) [\(kPa\)]

Data used for calibrating the correlation

Reference - Andersen KH. Cyclic soil parameters for offshore foundation design. The Third ISSMGE McClelland Lecture. In: Meyer V, editor. Proc. Int. Symp. Frontiers in offshore geotechnics, ISFOG 2015. London: Taylor and Francis; 2015. 5–82.

groundhog.siteinvestigation.correlations.cohesive.k0_plasticity_kenney(pi, ocr=1, coeff_1=0.19, coeff_2=0.233, coeff_3=-281, coeff_4=1.85, **kwargs)

Calculates the coefficient of lateral earthpressure at rest for normally and overconsolidated clay. Kenney (1959) presented a formula for coefficient of lateral earth pressure at rest for normally consolidated clay. The plasticity index \(\text{PI}\) was used as a basis for this correlation. This relation was modified for the effect of overconsolidation as shown by Alpan (1967). The exponent on OCR shows a linear variation with plasticity index.

Parameters:

• pi – Plasticity index (\(\text{PI}\)) [\(pct\)] - Suggested range: 5 <= PI <= 80

• ocr – Overconsolidation ratio (\(\text{OCR}\)) [\(-\)] (optional, default= 1, suggested range: 1 <= OCR < 30)

• coeff_1 – First calibration coefficient (optional, default=0.19)

• coeff_2 – Second calibration coefficient (optional, default=0.233)

• coeff_3 – First calibration coefficient (optional, default=-281)

• coeff_4 – Second calibration coefficient (optional, default=1.85)

\[ \begin{align}\begin{aligned}K_{0,NC} = 0.19 + 0.233 \log_{10} I_p\\I_p = -281 \log_{10} \left( 1.85 \lambda \right)\end{aligned}\end{align} \]

Returns:

Dictionary with the following keys:

• ’K0 NC [-]’: Coefficient of lateral earth pressure at rest for normally consolidated conditions (\(K_{0,NC}\)) [\(-\)]

• ’K0 [-]’: Coefficient of lateral earth pressure at rest (\(K_0\)) [\(-\)]

Reference - Alpan (1967) THE EMPIRICAL EVALUATION OF THE COEFFICIENT K0 AND K0R. Soils and Foundations. Volume 7, Issue 1