DESIGN AND ANALYSIS OF DEEP FOUNDATIONS FOR MULTI-STORY BUILDING STRUCTURES
Lecturer : Dyah Ayu Rahmawati Cupasindy, S.ST., M,T
Group :
1. Ferdhie Audito 2241320087
2. Muhammad Farhan P.S 2241320087
3. Mumtaz Syarif Avito 2241320107
D-IV CONSTRUCTION ENGINEERING MANAGEMENT CIVIL ENGINEERING DEPARTMENT
STATE POLYTECHNIC OF MALANG
2025
CHAPTER 1 INTRODUCTION 1.1 Backgroud
Design and Analysis of Deep Foundations for Multi-Story Building Structures Deep foundations are a critical component in the design of multi-story building structures, particularly in areas with unstable soil conditions or high structural loads. The primary function of deep foundations is to transfer the building's load to deeper, more competent soil layers, ensuring the stability and safety of the structure. Common types of deep foundations include driven piles, bored piles, and caissons, which are selected based on geotechnical analysis and structural requirements.
The design process for deep foundations begins with a thorough soil investigation, including field and laboratory tests, to determine soil parameters such as bearing capacity, skin friction, and deformation characteristics. This data is then used to model the behavior of the foundation and soil under both static and dynamic loads. Structural analysis is conducted to ensure that the foundation can withstand dead loads, live loads, and lateral forces such as those from earthquakes or wind.
Additionally, factors such as soil-structure interaction and potential settlement must be considered to prevent damage to the building. Modern technologies, including 3D modeling and computer simulations, have significantly enhanced the accuracy of deep foundation design. Through a comprehensive approach, the design and analysis of deep foundations ensure the reliability and longevity of multi-story building structures.
1.2 Research Question
1) How do soil characteristics influence the selection of the most effective type of deep foundation for multi-story building structures?
2) Which analysis methods are most accurate in predicting soil-structure interaction for deep foundations?
3) What is the impact of lateral loads, such as earthquakes or wind, on the performance of deep foundations in multi-story buildings?
4) How does uneven settlement affect the stability of multi-story building structures, and what strategies can minimize it?
5) What is the performance comparison between driven piles and bored piles in supporting the loads of multi-story building structures?
6) How do environmental conditions, such as groundwater or corrosion, affect the durability and performance of deep foundations?
7) What are the best methods for monitoring and evaluating the performance of deep foundations during construction and operational phases?
8) How can deep foundation designs be optimized to reduce construction costs without compromising safety and structural performance?
9) What are the main challenges in designing deep foundations for multi-story buildings in areas with complex geotechnical conditions, such as soft soil or earthquake-prone regions?
1.3 Purpose
1) To understand the influence of soil characteristics on the selection of optimal deep foundation types for multi-story buildings.
2) To develop more accurate analysis methods for predicting soil-structure interaction in deep foundations.
3) To evaluate the performance of deep foundations in resisting lateral loads, such as earthquakes or wind, to enhance structural safety.
4) To minimize the risk of uneven settlement through more effective deep foundation design.
5) To compare the performance of various deep foundation types, such as driven piles and bored piles, to determine the best solution based on project conditions.
6) To analyze the impact of environmental conditions on the durability of deep foundations and propose solutions to enhance their resilience.
7) To develop systems for monitoring the performance of deep foundations during construction and operational phases.
8) To optimize deep foundation designs to reduce construction costs without compromising reliability and structural safety.
9) To identify and address challenges in designing deep foundations for multi- story buildings in areas with complex geotechnical conditions.
1.4 Research Benefits
Mahasiswa & instansi 1.5 Scope of Problem
In research on the design and analysis of foundations for multi-story building structures, the scope of the problem is quite broad, namely covering technical, environmental and practical aspects.The following is the scope of the problems that will be discussed:
1) Soil Characteristics:
In-depth analysis of soil properties, such as bearing capacity, skin friction, and settlement potential, which influence the selection and design of deep foundations.
2) Selection of Deep Foundation Types:
Evaluation of various deep foundation types, such as driven piles, bored piles, or caissons, to determine the most suitable option based on soil conditions and structural loads.
3) Soil-Structure Interaction:
Study of how deep foundations interact with the surrounding soil, including load distribution and deformation behavior.
4) Lateral and Dynamic Loads:
Analysis of the ability of deep foundations to withstand lateral loads, such as earthquakes or wind, as well as the impact of dynamic loads on foundation performance.
5) Settlement and Its Effects:
Investigation of potential uneven settlement and its impact on the stability and safety of the building structure.
6) Environmental Impacts:
Examination of the effects of environmental conditions, such as groundwater, corrosion, or climate change, on the durability and performance of deep foundations.
7) Technology and Analysis Methods:
Utilization of modern technologies, such as 3D modeling and computer simulations, to enhance the accuracy and efficiency of deep foundation design and analysis.
8) Design Optimization and Cost Efficiency:
efforts to design cost-efficient deep foundations without compromising structural safety and performance.
9) Performance Monitoring and Evaluation:
Development of methods to monitor and evaluate the performance of deep foundations during construction and operational phases.
10) Challenges in Complex Geotechnical Conditions:
Identification and solutions for challenges in designing deep foundations in areas with difficult soil conditions, such as soft soil, earthquake-prone regions, or locations with high groundwater levels.
11) Compliance with Standards and Regulations:
Ensuring that the design and analysis of deep foundations comply with applicable national and international standards and regulations.
12) Case Studies and Practical Applications:
Analysis of case studies from multi-story building projects to evaluate the effectiveness of implemented deep foundation designs.
CHAPTER 2
LITERATURE REVIEW
2.1Definition and Types of Deep Foundations 2.1.1Definition of Deep Foundations
Deep foundations are structural elements used to transfer the load of a building or structure to deeper, more stable soil or rock layers when the surface soil lacks sufficient bearing capacity or is otherwise unsuitable. They are typically employed for large or heavy structures, such as multi-story buildings, bridges, and towers, especially in areas with weak, compressible, or unstable surface soils. Deep foundations bypass the weaker upper soil layers and distribute the structural load to stronger, deeper strata, ensuring stability and minimizing settlement
.
2.1.2 Types of Deep Foundations
Deep foundations can be categorized into several types based on their construction methods, materials, and load-transfer mechanisms. The most common types include:
1. Piles:
a. Driven Piles: Prefabricated piles (made of concrete, steel, or timber) are driven into the ground using impact or vibration hammers.
b. Bored Piles (Drilled Shafts): Holes are drilled into the ground, and then filled with concrete, often reinforced with steel.
c. Micro piles: Small-diameter piles used in areas with limited access or where minimal disturbance is required.
(Example pict of foundation piles)
2. Caissons:
a. Drilled Caissons: Large-diameter foundations drilled to great depths and filled with concrete. They are often used for heavy structures like bridges.
b. Floating Caissons: Prefabricated hollow structures that are floated to the site and sunk into place, then filled with concrete.
(Pict of Foundation Caissons)
3. Piers: Similar to caissons but typically larger in diameter and constructed by excavating a deep hole and filling it with concrete.
(Pict of Foundation Piers)
4. Helical Piles:
Steel shafts with helical plates that are screwed into the ground, providing immediate load-bearing capacity. They are often used for lightweight structures or in areas with difficult access.
(Pict of Foundation Helical Piles) 5. Composite Foundations:
Combinations of different foundation types, such as piles with raft foundations, to optimize load distribution and performance.
(Pict of Composite foundation)
2.1.3 Key Characteristics of Deep Foundation
1. Load Transfer Mechanism: Deep foundations transfer loads through end-bearing (resting on a strong layer) or skin friction (resistance along the sides of the foundation).
2. Depth: They extend significantly deeper than shallow foundations, often reaching tens of meters below the surface.
3. Applications: Ideal for heavy structures, weak surface soils, high groundwater levels, or areas prone to seismic activity.
2.2 Soil Parameters Affecting Foundation Performance
The performance of deep foundations is highly dependent on the properties of the soil in which they are embedded. Understanding these soil parameters is crucial for accurate design and analysis. The key soil parameters that influence foundation performance include.
2.2.1 Soil Type and Stratification
The type of soil (For example : clay, silt, sand, gravel, or rock) significantly affects the load-bearing capacity and settlement behavior of deep foundations. For example, cohesive soils like clay have high shear strength but may exhibit long-term consolidation settlement, while granular soils like sand provide better drainage and immediate load-bearing capacity.
The arrangement of soil layers determines how loads are transferred through the soil profile. A detailed understanding of soil stratification helps in selecting the appropriate depth and type of deep foundation.
2.2.2 Bearing Capacity
Ultimate Bearing Capacity : The maximum load per unit area that the soil can support without failure. It is influenced by soil cohesion, internal friction angle, and foundation dimensions.
(Pict of Ultimate Bearing Capacity) (Pict of Mayerhof Bearing Capacity)
Allowable Bearing Capacity : The safe load-bearing capacity, which is derived by applying a factor of safety to the ultimate bearing capacity. It ensures the foundation operates within safe limits.
2.2.3 Shear Strength
The inherent shear strength of cohesive soils like clay, which arises from electrostatic forces between soil particles (c).
A measure of the shear strength of granular soils like sand, which depends on the interlocking of soil particles and confining pressure (φ).
(Pict of Shear Strength of Soil)
2.2.4 Settlement Characteristics
a) Immediate Sattlement
Occurs immediately after load application, primarily in granular soils due to particle rearrangement.
b) Consolidation Sattlement
Occurs over time in cohesive soils due to the expulsion of water from the soil pores. It is a critical factor in clayey soils.
c) Differential Sattlement
Not evenly distributed settlement across the foundation, which can cause structural damage. It is influenced by variations in soil properties and loading conditions.
2.2.5 Modulus Of Subgrade Reaction
A measure of the soil's stiffness, indicating how much the soil resists deformation under load. It is essential for analyzing soil-structure interaction and designing foundations to minimize settlement.
(Pict of Modulus Of Subgrade Reaction)
2.2.6 Permeability
The ability of soil to transmit water, which affects drainage and pore water pressure. High permeability in granular soils allows for rapid drainage, while low permeability in cohesive soils can lead to excess pore pressure and reduced effective stress.
2.2.7 Elastic Modulus
A measure of soil stiffness, indicating how much the soil deforms under stress. It is critical for predicting settlement and deformation.
2.2.8 Soil Density
Density Affects the shear strength and compressibility of the soil.
Denser soils generally have higher bearing capacity and lower settlement.
The weight of soil per unit volume, which influences the overburden pressure and lateral earth pressure on the foundation.
2.2.9 Ground Water Conditions
The depth of the water table affects the effective stress in the soil. A high water table will reduce the effective stress, thereby lowering the bearing capacity of the soil, as well as the water pressure exerted on the foundation, which must be considered in the design to prevent buoyancy or instability.
(Pict of Ground Water Condition)
2.2.10Soil Liquefaction Potential
In earthquake-prone areas, water-saturated grained soils can experience a decrease in strength and behave like liquids due to increased pore water pressure. This phenomenon, called liquefaction, can cause serious failure of deep foundations.
(Description of Soil Liquefaction Potential)
2.2.11 Soil Corrosivity
The chemical composition of the soil can affect the durability of foundation materials, especially steel piles. Corrosive soils require protective measures, such as coatings or cathodic protection.
(Description of The Impact Soil Corrosivity)
2.2.12Soil Compressibility
The tendency of soil to decrease in volume under load. Highly compressible soils, such as soft clay, require special consideration to minimize settlement.
(Description of Soil Compressibility)
2.2.13Calculation methods for foundation bearing capacity (Terzaghi, mayerhof, etc.)
The bearing capacity of a foundation is the maximum load per unit area that the soil can support without undergoing shear failure or excessive settlement. Several
theoretical and empirical methods have been developed to calculate the bearing capacity of deep foundations. The most widely used methods include those proposed by Terzaghi, Meyerhof, Vesic, and Hansen. Each method considers different factors, such as soil properties, foundation geometry, and loading conditions.
2.2.14Terzaghi’s Bearing Capacity Theory
Terzaghi (1943) was one of the first to develop a comprehensive theory for calculating the bearing capacity of shallow and deep foundations.
His method is based on the assumption that the soil is homogeneous, isotropic, and behaves as a rigid-plastic material.
qu=cNc+qNq+0.5γBNγ Where :
c = cohesion of the soil
q = effective overburden pressure at the foundation base (q=γDfq=γDf) γγ = unit weight of the soil
B = width or diameter of the foundation Df = depth of the foundation
Nc, Nq, Nγ = bearing capacity factors, which depend on the soil's angle of internal friction (ϕϕ)
Bearing Capacity Factors : Nc = Nq−1
tanϕ
Nq=eπtanϕtan2
(
45∘+ϕ2)
Nγ = 2(Nq+1) tanϕ
Terzaghi’s method is widely used for cohesive and cohesionless soils but is limited to shallow foundations. For deep foundations, modifications are required to account for the depth effect.
2.2.15Meyerhof’s Bearing Capacity Theory
Meyerhof (1963) extended Terzaghi’s theory to include the effects of foundation shape, depth, and inclination of loads. His method is more versatile and applicable to both shallow and deep foundations.
qu=cNcscdc+qNqsqdq+0.5γBNγsγdγ Where :
sc, sq, sγ = shape factors dc, dq, dγ = depth factors Shape Factor :
sc=1+0.2B
Ltan2
(
45∘+ϕ2)
sq=sγ=1+0.1B
Ltan2
(
45∘+ϕ2)
L = length of the foundation.
Depth Factor :
dc=1+0.2Df
B tan
(
45∘+ϕ2)
dq=dγ=1+0.1Df
B tan
(
45∘+ϕ2)
Meyerhof’s method is particularly useful for deep foundations because it accounts for the increased bearing capacity due to the depth of
embedment.
2.2.16Derivation of Settlement Equations
Foundation settlement consists of three main types:
a) Immediate Settlement
Calculated using elasticity theory:
Si=qB
(
1−ν2)
E Is Where:
q = stress at the foundation base
B = foundation width ν = soil Poisson’s ratio E = soil elastic modulus
Is = influence factor for foundation shape
Consolidation Settlement Using Terzaghi’s theory:
Sc= Cc
1+e0Hlog
(
σσ0f)
Where:
Cc = compression index e0 = initial void ratio H = soil layer thickness σf = final effective stress σ0 = initial effective stress
Differential Settlement
Differential settlement is calculated as:
Sd=Smax−Smin
Where Smax and Smin are the settlements at different points of the foundation.
2.2.17Derivation of Soil Shear Strength Formula
Soil shear strength consists of two components:
Cohesive Soil (Clay):
τ=c+σtanϕ
Where:
τ = shear stress c = soil cohesion σ = normal stress
ϕ = internal friction angle
Granular Soil (Sand):
For cohesionless soil (c=0c):
τ = σ tan ϕ
2.2.18Derivation of Liquefaction Effect on Deep Foundations
In seismic conditions, saturated sandy soils may undergo liquefaction. The factor of safety against liquefaction is given by:
FS=CRR CSR Where:
CRR = cyclic resistance ratio of the soil CSR = cyclic stress ratio, calculated as:
CSR=0.65τmax σv' 1FS<1, liquefaction is likely to occur.
2.3Safety factors and design criteria
The design of deep foundations requires the application of safety factors and adherence to specific design criteria to ensure structural stability, durability, and performance under various loading and environmental conditions. Safety factors account for uncertainties in soil properties, load estimations, and construction practices, while design criteria provide guidelines for load capacity, settlement, and compliance with standards.
2.3.1 Safety Factors
1. Factor of Safety (FS) for Bearing Capacity: The ultimate bearing capacity (ququ) is divided by a factor of safety (typically 2.5 to 3.0) to obtain the allowable bearing capacity (qaqa), ensuring the foundation operates within safe limits.
2. Factor of Safety for Settlement: Predicted settlement must be less than allowable limits (e.g., 25 mm for isolated foundations and 50 mm for raft foundations) to prevent structural damage.
3. Factor of Safety for Lateral Loads: Additional safety margins are applied to resist lateral forces from wind or earthquakes.
4. Factor of Safety for Material Strength: Material strengths are reduced by safety factors to account for variability in properties and construction quality.
2.3.2 Criteria Design
a) Load Criteria: Foundations must withstand dead loads, live loads, and environmental loads (e.g., wind, earthquakes) using specified load combinations (e.g., 1.2DL + 1.6LL).
b) Settlement Criteria: Total settlement should not exceed 25 mm for isolated foundations or 50 mm for raft foundations, with differential settlement limited to 10-20 mm.
c) Geotechnical Criteria: Foundations must safely transfer loads without exceeding the allowable bearing capacity, account for soil-structure interaction, and resist liquefaction in seismic zones.
d) Structural Criteria: Foundations must be strong, durable, and constructible, with materials resistant to corrosion or chemical attack.
e) Environmental Criteria: Designs must consider groundwater effects, buoyancy, and minimize environmental disruption.
f)
Code Compliance: Designs must adhere to relevant standards, such as ACI 318, Eurocode 7, or SNI 8460.In foundation planning, several practical aspects need to be considered. The design should be adapted to the geotechnical and environmental conditions at the project site. Regular monitoring and testing are required to ensure the foundation functions as planned. In addition, risks such as unexpected soil conditions should be identified and minimised to avoid problems in the future.
CHAPTER 3
DATA AND SITE CONDITION
3.1 Soil Profile and Characteristics
Berdasarkan hasil pengeboran geoteknik dan pekerjaan SPT, diketahui lapisan tanah keras dengan NSPT>40 bervariatif antar titik pengujian yang sudah dilakukan.
Berdasarkan hasil pekerjaan CPT, diketahui lapisan tanah cukup keras dengan qc ≥ 250 kg/cm2 bervariatif antar titik pengujian yang sudah dilakukan.
Berdasarkan data laboratorium, didapatkan rangkuman data sebagai berikut:
3.2 Structural Load
3.3 Enviromental Condition
Berdasarkan pengujian SPT, didapatkan data sebagai berikut yang tercantum data kedalaman muka air tanah.
