Chapter 6 Enginereing Sustainability: Sustainable Geotech

Chapter 6 Enginereing Sustainability: Sustainable Geotech#

Introduction: Sustainable Geotech
Simulation: Sustainable Geotech
Self-Assessment

1. Introduction#

Descriptive alt text for accessibility — Fig. 43 **Figure 6.10 **: Sustainable Geotechnical Engineering#

🌱 Sustainable Geotechnical Engineering: Overview#

Sustainable geotechnics applies environmental, economic, and social principles to geotechnical design, construction, and maintenance. It aims to reduce the ecological footprint of infrastructure while maintaining safety and performance.

🧭 Key Strategies#

Material Optimization
Use of recycled aggregates, low-carbon concrete, and geosynthetics to reduce embodied carbon
Design Efficiency
Ground improvement techniques (e.g., vibro compaction, rigid inclusions) to minimize deep foundations
Energy Integration
Incorporation of geothermal systems and energy-harvesting sensors in foundations
Life Cycle Assessment (LCA)
Evaluate environmental impacts from cradle to grave using ISO 14040/14044 frameworks
Sustainability Rating Tools
Use of Envision and other SATs to guide sustainable infrastructure planning
Digital Innovation
AI, IoT, and machine learning for optimized site characterization and real-time monitoring

🚀 Opportunities#

Carbon Reduction
Sustainable geotechnics can reduce emissions by 35–90% in foundation systems through material substitution and design optimization
Resource Conservation
Reuse of existing foundations and materials reduces waste and conserves natural resources
Resilience and Adaptation
Designs that account for climate risks (e.g., liquefaction, flooding) improve long-term sustainability
Interdisciplinary Collaboration
Integration with environmental science, urban planning, and renewable energy sectors

⚠️ Challenges#

Higher Upfront Costs
Sustainable materials and techniques may require greater initial investment
Limited Material Availability
Access to low-carbon alternatives varies regionally
Regulatory Gaps
Lack of standardized sustainability mandates in geotechnical codes
Stakeholder Alignment
Balancing cost, performance, and sustainability across diverse project teams

🌍 Climate Impact Potential#

Geotechnical construction contributes 15–23% of a building’s embodied carbon. By adopting sustainable practices—such as avoiding concrete-heavy foundations, optimizing design, and using alternative fuels—projects have demonstrated carbon savings of over 90%, translating to tens of thousands of metric tons of CO₂e avoided.

📘 Summary Insight#

Sustainable geotechnical engineering is not only feasible—it’s essential. Through innovative materials, smarter design, and life cycle thinking, geotechnical professionals can lead the charge in reducing emissions, conserving resources, and building resilient infrastructure. The path forward requires collaboration, education, and bold adoption of emerging technologies.

References#

[European Federation of Foundation Contractors (EFFC) and Deep Foundations Institute (DFI), 2022] is the Geotechnical Carbon Calculator, which calculates CO₂ emissions for foundation and geotechnical works using standardized, verifiable data. The calculator enables comparison of design alternatives and tracks performance from planning to post-construction. The calculator is tailored specifically for geotechnical projects, making it the only sector-specific carbon tool of its kind

[Geo-Institute Sustainability in Geotechnical Engineering Committee, 2022] Links geotechnical practice to UN SDGs, emphasizing resilience, stakeholder engagement, and holistic design. Defines sustainability for geotechnical engineers using ASCE ethics and the Brundtland framework. It introduces tools like LCA, LCCA, and carbon calculators for project-level assessment, including case studies on ground improvement and pile foundations with quantified impacts.

🧱 Theoretical Background: Sustainable Geotechnical Engineering Calculator#

📘 Overview#

This calculator estimates the environmental and structural performance of common foundation systems—shallow footings, pile foundations, and retaining walls—based on user-defined geometry and soil parameters. It integrates:

Engineering design models for bearing capacity, axial pile capacity, and earth pressure
Material quantity estimation for concrete, steel, and geosynthetics
Embodied carbon and life cycle cost calculations
A sustainability scoring system based on reuse, emissions, and cost

📐 Engineering Models#

1. Shallow Foundation Bearing Capacity#

Based on Terzaghi’s equation for strip footings:

\[ q_{\text{ult}} = c N_c + q N_q + 0.5 \gamma B N_\gamma \]

$( c $): soil cohesion (kPa)
$( q $): overburden pressure (kPa)
$( \gamma $): unit weight of soil (kN/m³)
$( B $): footing width (m)
$( N_c, N_q, N_\gamma $): bearing capacity factors (empirical)

2. Pile Foundation Axial Capacity#

Simplified model combining skin friction and end bearing:

\[ Q_{\text{ult}} = \alpha c \pi L + c A_p N_c \]

$( \alpha $): adhesion factor (typically 0.6)
$( c $): cohesion
$( L $): pile length (m)
$( A_p $): pile cross-sectional area (m²)
$( N_c $): bearing capacity factor (typically 9 for cohesive soils)

3. Retaining Wall Earth Pressure#

Using Rankine’s active earth pressure theory:

\[ P_a = \frac{1}{2} \gamma H^2 K_a \quad \text{where} \quad K_a = \frac{1 - \sin(\phi)}{1 + \sin(\phi)} \]

$( \gamma $): unit weight of soil
$( H $): wall height (m)
$( \phi $): internal friction angle (°)

🌍 Sustainability Metrics#

1. Embodied Carbon#

Calculated using emission factors:

Material	Emission Factor (kg CO₂/kg)
Concrete	0.15
Steel	1.85
Geosynthetics	2.50

\[ \text{Carbon} = \sum (\text{mass}_i \times \text{emission factor}_i) \]

2. Life Cycle Cost#

Estimated using unit costs:

Material	Cost ($/kg)
Concrete	0.10
Steel	1.20
Geosynthetics	2.00

\[ \text{Cost} = \sum (\text{mass}_i \times \text{unit cost}_i) \]

3. Sustainability Score#

Empirical scoring system (0–10):

+2 if reuse ≥ 50%
+2 if carbon < 500 kg CO₂
+1 if cost < $1000

📊 Material Estimation#

Concrete volume is calculated from geometry:

Shallow footing: $( V = B \times B \times D $)
Pile: $( V = A_p \times L $)
Retaining wall: $( V = H \times t_{\text{wall}} \times L_{\text{wall}} $)

Steel mass is estimated using typical reinforcement ratios:

Foundation Type	Steel Ratio (kg/m³)
Shallow Footing	100
Pile Foundation	120
Retaining Wall	150

📚 References and Sources#

Terzaghi, K. (1943). Theoretical Soil Mechanics. Wiley.
Das, B.M. (2010). Principles of Foundation Engineering. Cengage.
Rankine, W.J.M. (1857). On the Stability of Retaining Walls. Philosophical Transactions.
Hammond, G.P., & Jones, C.I. (2008). Embodied energy and carbon in construction materials. ICE Proceedings.
World Bank (2020). Low Carbon Construction Materials: Cost and Emissions Benchmarks.

📥 Typical Input Ranges#

Parameter	Typical Range
Cohesion $( c $)	0–100 kPa
Unit Weight $( \gamma $)	16–22 kN/m³
Friction Angle $( \phi $)	25–40°
Reuse Percentage	0–100%
Concrete Density	2400 kg/m³
Steel Reinforcement	100–150 kg/m³

2. Simulation#

import numpy as np
import matplotlib.pyplot as plt
import ipywidgets as widgets
from IPython.display import display, clear_output

# Emission and cost factors
emission_factors = {"concrete": 0.15, "steel": 1.85, "geosynthetic": 2.5}
cost_factors = {"concrete": 0.10, "steel": 1.20, "geosynthetic": 2.00}

# Engineering models
def bearing_capacity(c, gamma, B, q):
    Nc, Nq, Ngamma = 5.14, 1.0, 0.0
    return c * Nc + q * Nq + 0.5 * gamma * B * Ngamma

def pile_capacity(c, Ap, L, alpha=0.6):
    Qs = alpha * c * np.pi * L
    Qp = c * Ap * 9
    return Qs + Qp

def earth_pressure(gamma, H, phi):
    Ka = (1 - np.sin(np.radians(phi))) / (1 + np.sin(np.radians(phi)))
    return 0.5 * gamma * H**2 * Ka

def sustainability_score(reuse_pct, carbon, cost):
    score = 5
    if reuse_pct >= 50: score += 2
    if carbon < 500: score += 2
    if cost < 1000: score += 1
    return max(min(score, 10), 0)

# Material estimation
def estimate_materials(foundation_type, B, D, Ap, L, H, t_wall, wall_length):
    if foundation_type == "Shallow":
        V_conc = B * B * D
        steel_ratio = 100
    elif foundation_type == "Pile":
        V_conc = Ap * L
        steel_ratio = 120
    elif foundation_type == "Retaining Wall":
        V_conc = H * t_wall * wall_length
        steel_ratio = 150
    else:
        V_conc = 0
        steel_ratio = 0
    concrete_kg = V_conc * 2400
    steel_kg = V_conc * steel_ratio
    return concrete_kg, steel_kg

# Widgets
foundation_dropdown = widgets.Dropdown(
    options=["Shallow", "Pile", "Retaining Wall", "Geosynthetic-Reinforced"],
    description='Type'
)
reuse_slider = widgets.FloatSlider(value=0, min=0, max=100, step=10, description='Reuse (%)')
geo_slider = widgets.FloatSlider(value=200, min=0, max=1000, step=50, description='Geosynthetics (kg)')

# Geometry
B_slider = widgets.FloatSlider(value=2.0, min=0.5, max=5.0, step=0.1, description='Footing Width (m)')
D_slider = widgets.FloatSlider(value=0.5, min=0.2, max=2.0, step=0.1, description='Footing Depth (m)')
Ap_slider = widgets.FloatSlider(value=0.2, min=0.05, max=1.0, step=0.05, description='Pile Area (m²)')
L_slider = widgets.FloatSlider(value=10, min=2, max=30, step=1, description='Pile Length (m)')
H_slider = widgets.FloatSlider(value=4, min=1, max=10, step=0.5, description='Wall Height (m)')
t_wall_slider = widgets.FloatSlider(value=0.3, min=0.2, max=1.0, step=0.05, description='Wall Thickness (m)')
wall_length_slider = widgets.FloatSlider(value=6, min=2, max=20, step=1, description='Wall Length (m)')

# Soil
c_slider = widgets.FloatSlider(value=25, min=0, max=100, step=5, description='Cohesion (kPa)')
gamma_slider = widgets.FloatSlider(value=18, min=10, max=22, step=1, description='Unit Weight (kN/m³)')
q_slider = widgets.FloatSlider(value=30, min=0, max=100, step=5, description='Overburden (kPa)')
phi_slider = widgets.FloatSlider(value=30, min=20, max=45, step=1, description='Friction Angle (°)')

# Output and button
output = widgets.Output()
run_button = widgets.Button(description="Run Analysis", button_style='success')

# Update visible inputs
def update_visibility(change=None):
    with output:
        clear_output()
        base = [foundation_dropdown, reuse_slider, geo_slider]
        if foundation_dropdown.value == "Shallow":
            inputs = base + [B_slider, D_slider, c_slider, gamma_slider, q_slider]
        elif foundation_dropdown.value == "Pile":
            inputs = base + [Ap_slider, L_slider, c_slider]
        elif foundation_dropdown.value == "Retaining Wall":
            inputs = base + [H_slider, t_wall_slider, wall_length_slider, gamma_slider, phi_slider]
        else:
            inputs = base
        display(widgets.VBox(inputs + [run_button]))

# Compute results
def compute_results(button=None):
    with output:
        clear_output(wait=True)
        concrete_kg, steel_kg = estimate_materials(
            foundation_dropdown.value,
            B_slider.value, D_slider.value,
            Ap_slider.value, L_slider.value,
            H_slider.value, t_wall_slider.value,
            wall_length_slider.value
        )
        concrete_eff = concrete_kg * (1 - reuse_slider.value / 100)
        steel_eff = steel_kg * (1 - reuse_slider.value / 100)
        geo_eff = geo_slider.value * (1 - reuse_slider.value / 100)

        carbon = (concrete_eff * emission_factors["concrete"] +
                  steel_eff * emission_factors["steel"] +
                  geo_eff * emission_factors["geosynthetic"])
        cost = (concrete_eff * cost_factors["concrete"] +
                steel_eff * cost_factors["steel"] +
                geo_eff * cost_factors["geosynthetic"])
        score = sustainability_score(reuse_slider.value, carbon, cost)

        if foundation_dropdown.value == "Shallow":
            result = bearing_capacity(c_slider.value, gamma_slider.value, B_slider.value, q_slider.value)
            label = "Ultimate Bearing Capacity (kPa)"
        elif foundation_dropdown.value == "Pile":
            result = pile_capacity(c_slider.value, Ap_slider.value, L_slider.value)
            label = "Axial Pile Capacity (kN)"
        elif foundation_dropdown.value == "Retaining Wall":
            result = earth_pressure(gamma_slider.value, H_slider.value, phi_slider.value)
            label = "Active Earth Pressure (kN/m)"
        else:
            result = "N/A"
            label = "Performance Metric"
        # 📘 Interpretation and Summary
        print("\n📘 Interpretation:")

        # Embodied carbon interpretation
        if carbon < 500:
            print("✅ Low embodied carbon — aligns with sustainable construction targets.")
        elif carbon < 800:
            print("⚠️ Moderate embodied carbon — better than conventional but could improve.")
        else:
            print("❌ High embodied carbon — consider reducing concrete or increasing reuse.")

        # Cost interpretation
        if cost < 1000:
            print("✅ Economical design — suitable for budget-sensitive projects.")
        elif cost < 1500:
            print("⚠️ Moderate cost — acceptable for performance-driven applications.")
        else:
            print("❌ High cost — consider optimizing material use or sourcing.")

        # Strength interpretation
        if foundation_dropdown.value == "Shallow" and result < 150:
            print("⚠️ Low bearing capacity — may not be suitable for heavy loads.")
        elif foundation_dropdown.value == "Pile" and result < 500:
            print("⚠️ Low axial capacity — consider increasing pile length or diameter.")
        elif foundation_dropdown.value == "Retaining Wall" and result < 20:
            print("⚠️ Low earth pressure — verify soil parameters.")
        else:
            print("✅ Structural performance appears adequate for typical conditions.")

        # Sustainability score interpretation
        if score >= 8:
            print("✅ High sustainability score — excellent balance of cost, carbon, and reuse.")
        elif score >= 5:
            print("⚠️ Moderate sustainability — room for improvement.")
        else:
            print("❌ Low sustainability — redesign recommended.")

        # 📊 Summary Table
        print("\n📊 Summary Compared to Typical Values:")
        print(f"{'Metric':<25}{'Your Design':>15}{'Typical Range':>20}")
        print("-" * 60)
        print(f"{'Embodied Carbon (kg CO₂)':<25}{carbon:>15.1f}{'300–800':>20}")
        print(f"{'Life Cycle Cost ($)':<25}{cost:>15.2f}{'800–1500':>20}")
        print(f"{label:<25}{result if isinstance(result, str) else f'{result:.1f}':>15}{'Depends on type':>20}")
        print(f"{'Sustainability Score':<25}{score:>15}{'5–10':>20}")

        
        
        print(f"🏗️ Foundation Type: {foundation_dropdown.value}")
        print(f"Concrete Volume: {concrete_kg / 2400:.2f} m³")
        print(f"Concrete Used: {concrete_eff:.1f} kg")
        print(f"Steel Used: {steel_eff:.1f} kg")
        print(f"Geosynthetics Used: {geo_eff:.1f} kg")
        print(f"Reuse Percentage: {reuse_slider.value}%")
        print(f"\n🌍 Embodied Carbon: {carbon:.2f} kg CO₂")
        print(f"💰 Life Cycle Cost: ${cost:.2f}")
        print(f"📏 {label}: {result if isinstance(result, str) else f'{result:.1f}'}")
        print(f"🧠 Sustainability Score: {score}/10")

        categories = ['Carbon (kg CO₂)', 'Cost ($)', 'Sustainability']
        values = [carbon, cost, score]
        colors = ['gray', 'green', 'blue']

        plt.figure(figsize=(7, 4))
        plt.bar(categories, values, color=colors)
        plt.title("Sustainable Geotechnical Metrics")
        plt.ylabel("Value")
        plt.grid(True)
        plt.tight_layout()
        plt.show()

# Link triggers
foundation_dropdown.observe(update_visibility, names='value')
run_button.on_click(compute_results)

# Initial display
update_visibility()
display(output)

3. Self-Assessment#

🧱 Reflective, Conceptual, and Quiz Questions: Sustainable Geotechnical Engineering Calculator#

📘 Conceptual Questions#

These questions explore the engineering principles, sustainability metrics, and modeling logic behind the calculator.

Foundation Design#

What are the key differences in load transfer mechanisms between shallow and deep foundations?
How does geometry (e.g., footing width, pile length, wall height) influence material demand and structural performance?
Why is bearing capacity estimated using Terzaghi’s equation for shallow foundations?

Material Estimation#

How is concrete volume estimated from geometric inputs, and why is density used to convert to mass?
What assumptions are made about steel reinforcement ratios in different foundation types?
How does material reuse affect both embodied carbon and cost?

Sustainability Metrics#

Why is embodied carbon a critical metric in geotechnical design?
How does the sustainability score balance environmental and economic performance?
What are the limitations of using fixed emission and cost factors across diverse project contexts?

🔍 Reflective Questions#

These questions encourage critical thinking and application to real-world design decisions.

If your project site has soft clay and high water table, which foundation type would you choose and why?
How would your design change if the goal was to minimize embodied carbon rather than maximize bearing capacity?
What trade-offs exist between increasing wall thickness for strength and reducing material use for sustainability?
How could this model be extended to include excavation impacts or construction equipment emissions?
What policy or procurement strategies could incentivize reuse of foundation materials?

❓ Quiz Questions#

Multiple Choice#

Which foundation type typically requires the greatest volume of concrete per unit area?
A. Shallow footing
B. Pile foundation
C. Retaining wall
D. Geosynthetic-reinforced soil
Answer: B
What is the primary factor influencing axial capacity of a pile in cohesive soil?
A. Pile diameter
B. Soil friction angle
C. Cohesion and pile length
D. Wall height
Answer: C
Which parameter most directly affects active earth pressure on a retaining wall?
A. Wall thickness
B. Soil cohesion
C. Friction angle and wall height
D. Pile area
Answer: C

True/False#

Increasing reuse percentage reduces both embodied carbon and material cost.
Answer: True
The sustainability score increases if the design uses more concrete.
Answer: False
Steel reinforcement is assumed to scale linearly with concrete volume in this model.
Answer: True

Short Answer#

Explain how the calculator estimates concrete mass from geometric inputs.
Answer: It calculates volume based on foundation geometry and multiplies by concrete density (2400 kg/m³) to estimate mass.
What are the environmental benefits of using geosynthetics in foundation systems?
Answer: Geosynthetics can reduce the need for bulk materials, improve soil performance, and enable reuse or modular design, lowering overall carbon footprint.

Parameter	Typical Range
Cohesion \(( c \))	0–100 kPa
Unit Weight \(( \gamma \))	16–22 kN/m³
Friction Angle \(( \phi \))	25–40°
Reuse Percentage	0–100%
Concrete Density	2400 kg/m³
Steel Reinforcement	100–150 kg/m³