Chapter 3: Earthquake Engineering & Soil Dynamics¶

Chapter Context & Source Papers

This chapter synthesizes technical papers from Session 3 (Earthquake and Soil Dynamics) presented at GAIC 2025 and published in GeoVadis: The Future of Geotechnical Engineering (Volume 3), CRC Press / Taylor & Francis (2026), DOI: 10.1201/9781003645955.

1. Executive Summary & Dynamic Focus¶

Session 3 addressed non-linear seismic soil response across complex infrastructure systems:

flowchart TD
    S3["Session 3: Earthquake & Soil Dynamics"]
    S3 --> ZD["Zoned Embankment Dams<br/>Nonlinear dynamic response<br/>Crest settlement & shear strain"]
    S3 --> PL["Particle-Scale Liquefaction<br/>DEM contact mechanics<br/>Void ratio vs coordination number"]
    S3 --> QW["Port Quay Walls<br/>Performance-based design<br/>Indian vs Japanese seismic codes"]
    S3 --> MD["Glacial Lake Moraine Dams<br/>Imja Lake seismic breach risk<br/>Kobe vs Chile strong ground motions"]
    S3 --> CF["Circular Footing Impedance<br/>Dynamic soil-foundation interaction<br/>Frequency-dependent compliance"]

2. Non-Linear Seismic Response of Zoned Embankment Dams (Kumar & Maheshwari)¶

A. Kumar and Prof. B.K. Maheshwari evaluated the non-linear earthquake response of high zoned rockfill dams with central impervious clay cores:

Constitutive Formulation: Equivalent linear vs. fully non-linear hysteretic elastoplastic models with pressure-dependent shear modulus degradation \(G/G_{\text{max}}\) and damping ratio \(D\):

\[\frac{G}{G_{\text{max}}} = \frac{1}{1 + \left(\frac{\gamma}{\gamma_r}\right)^a}\]

Permanent Deformation Prediction: Newmark sliding block integration versus coupled dynamic effective-stress finite element analyses. Under peak ground acceleration (\(PGA = 0.45\text{ g}\)), non-linear soil softening amplified permanent crest settlement by 42% compared to equivalent-linear approximations.
Excess Pore Pressure in Core: Core saturation levels dictated hydrodynamic stress redistribution; failure to model hydraulic-mechanical coupling underestimates downstream slope outward bulging.

3. Particle-Based Micromechanics for Liquefaction Susceptibility (Banerjee et al.)¶

S. Banerjee, R.K. Kandasami, M.U. Rehman, and A. Srivastava introduced a simplified particle-level discrete element method (DEM) framework to characterize liquefaction susceptibility:

Micro-to-Macro Contact Network: Coordination number \(Z_c\) and mechanical contact anisotropy tensor \(a_{ij}\):

\[Z_c = \frac{2 N_c}{N_p}\]

\[a_{ij} = \frac{15}{2} \left( \Phi_{ij} - \frac{1}{3}\delta_{ij} \right)\]

where \(N_c\) is contact count and \(N_p\) is particle count.

Liquefaction Triggering Criterion: During undrained cyclic shearing, liquefaction onset corresponds to a critical drop in active load-bearing coordination number (\(Z_c \rightarrow 3.0\)), causing macroscopic shear modulus \(G \rightarrow 0\) regardless of initial relative density \(D_r\).
Simplified Assessment Index: A dimensionless grain-scale metric linking uniformity coefficient \(C_u\), sphericity \(S\), and initial state parameter \(\psi\) was proposed, circumventing time-consuming cyclic triaxial testing for initial site screening.

4. Performance-Based Seismic Design of Port Quay Walls (Pushpa et al.)¶

K. Pushpa, P. Nanjundaswamy, and S.K. Prasad carried out a rigorous comparative review between Indian Standard (IS 1893 / IS 456) and Japanese Port Design Standards (OCDI - Overseas Coastal Development Institute of Japan):

Design Philosophy Comparison:
- Indian Standard: Force-based pseudo-static method using seismic coefficient \(k_h = \frac{Z \cdot I \cdot S_a / g}{2 R}\).
- Japanese Code (OCDI): Two-tier performance-based design:
  - Level 1 (Serviceability Earthquake - return period 75 yrs): Minor residual displacement (\(\Delta x < 0.1\text{ m}\)), immediate operational recovery.
  - Level 2 (Safety Earthquake - return period 475–1000 yrs): Controlled residual displacement (\(\Delta x < 0.3 - 0.5\text{ m}\)), no sudden collapse of caisson structure or loss of berth function.
Case Evaluation: Pseudo-static methods significantly underestimate residual lateral displacement and tilting when backfill liquefaction occurs behind the caisson wall, demonstrating the necessity of effective-stress dynamic response analyses in maritime infrastructure.

5. Seismic Stability of Glacial Lake Moraine Dams (Ojha, Tiwari, et al.)¶

Biraj Ojha, Aanchal Tiwari, Sandeep Sapkota, Ram Chandra Tiwari, and P. Dangi Chhetri investigated the seismic vulnerability of the Imja Glacier Lake moraine dam in the high Himalayas of Nepal:

Site Context: Imja Lake (\(5,010\text{ m}\) elevation) stores tens of millions of cubic meters of meltwater retained by an unconsolidated terminal moraine dam containing an ice core.
Seismic Excitation: Dam stability was simulated under historical strong ground motions (1995 Kobe \(M_w 6.9\) and 2010 Chile \(M_w 8.8\) earthquakes):

graph TD
    EQ["Strong Ground Motion (Kobe / Chile)"] --> Accel["High Crest Acceleration Amplification (Up to 2.1x)"]
    Accel --> Core["Ice-Core Degradation & Moraine Liquefaction"]
    Core --> Slide["Upstream / Downstream Slope Slumping (1.2 to 2.4 m)"]
    Slide --> Freeboard["Loss of Freeboard & GLOF (Glacial Lake Outburst Flood)"]

Outlet Channel Integrity: The artificial spillway channel was found prone to blockage from seismic raveling of adjacent moraine ridges, posing a critical cascading risk of overtopping and catastrophically triggering a Glacial Lake Outburst Flood (GLOF).

6. Dynamic Soil-Foundation Interaction of Circular Footings (Jafarzadeh & Maleki)¶

Fardin Jafarzadeh and Jafar Maleki investigated the dynamic impedance and vibration response of rigid circular surface footings on sand beds:

Experimental Testing: Large-scale dynamic test pit instrumented with accelerometers and contact pressure sensors excited under variable frequency vertical and rocking harmonics (\(f = 5 - 50\text{ Hz}\)).
Impedance Functions: Complex stiffness \(K^* = K_{dyn} + i \omega C\):

\[K_{dyn}(\omega) = k(\omega) K_s\]

\[C(\omega) = c(\omega) \frac{K_s r_0}{V_s}\]

where \(K_s = \frac{4 G r_0}{1 - \nu}\) is static vertical stiffness, and \(r_0\) is footing radius. * Non-Linear Strain Effects: At shear strain amplitudes \(\gamma > 10^{-4}\), foundation resonance frequencies shifted downward by 25% due to shear modulus degradation in the near-field zone, accompanied by a 35% increase in radiation damping.