Foundation Construction Methods

How we built over a live sewer for the extension element for our CIAT Awards shortlisted project.    Building over a sewer can be risky. The weight of a new structure can crush the pipe, leading to serious damage and costly repairs from the local water authority. To avoid this, we had to get creative. 💡    This sort of work is controlled under the Building Regulations and building over an existing sewer is only allowed if the building work 'is constructed or carried out in a manner which will not overload or otherwise cause damage to the drain, sewer or disposal main either during or after construction.'   First, I mapped out the existing drains and manholes to understand the depth and size of the pipes. We discovered they were over 2 metres deep, which meant we needed a specialised foundation system to bypass them.    After considering several options, I decided on piled foundations. This method uses deep "stilts" to transfer the building's weight well below the sewer pipe, ensuring no pressure is placed on it. This not only dealt with the risk to the sewer but also proved to be a safer, faster, and more cost-effective solution than the alternative which was 3m deep trench foundations.    The choice of roof structure also had an impact on the piled foundations and how they interacted with the sewer pipe. I proposed a cut timber roof supported off a steel ridge beam. This roof structure was designed to move loads to the long gable side wall of the extension [running parallel to the pipe] so the two short walls [on top of the pipe] were not as heavily loaded, this therefore reduced the loads above the sewer and the risk of the sewer being damaged. If trussed rafters had been used the loads would have been moved to the short walls thus increasing the loads on the existing sewers below. This detail was key to protecting the underground infrastructure.    To make this project even more interesting the piling sub-contractors who had been quite helpful pre-construction decided to change their T&C’s a week before installation. The Clients weren’t really happy with this late change so I helped source alternative piling sub-contractors at short notice who managed to turn things around in enough time. Was slightly stressful for a couple of weeks but we just about made it without any delay or cost changes.    We also had CCTV surveys completed before + during + after the building work to check the condition of the drains. This helped us identify if the drains were in good condition or if they had become damaged during the building work and needed some remedial repairs.    So, that’s how we successfully built over a live sewer.    I can’t stress how important the initial survey work is before design work is started, as this vital information will inform the initial and final design.    Wish me luck for the actual Chartered Institute of Architectural Technologists (CIAT) Awards event tomorrow in London, I’ll keep you posted! 😎

“The construction of the Burj Khalifa’s basement involved advanced deep piling techniques to ensure the stability of the world's tallest skyscraper. These deep piles were meticulously designed and installed to support the immense load of the building and withstand environmental stresses such as heavy winds and potential overloads. This foundational approach ensures long-term stability and safety, preventing any risk of structural failure due to these factors.” Certainly! Here’s a more detailed explanation of the real-world techniques and considerations involved in the basement construction of the Burj Khalifa: 1. Site Preparation and Excavation Geotechnical Analysis: Detailed geotechnical surveys provided crucial data about the soil composition, groundwater levels, and bedrock depth. This information was essential for designing the foundation system. Massive Excavation: Excavating the site involved removing approximately 60,000 cubic meters of earth. The excavation extended down to the bedrock, creating a large and deep pit. 2. Secant Pile Wall Construction: To support the excavation and prevent soil collapse, a secant pile wall was installed. This method involves drilling overlapping concrete piles into the ground, creating a solid barrier around the excavation site. Purpose: The secant pile wall helped to retain the surrounding earth and control groundwater ingress during construction. 3. Deep Pile Foundations Pile Design: The foundation utilized a combination of bored piles and a raft foundation. Bored piles, ranging from 1.5 to 2 meters in diameter and extending up to 50 meters deep, were drilled into the bedrock to anchor the building. Raft Foundation: Above the piles, a massive reinforced concrete raft, approximately 3.7 meters thick, was constructed. This raft distributes the building’s load evenly across the piles. 4. Reinforcement and Concrete Reinforcement: High-strength steel rebar was used extensively to reinforce the concrete, ensuring structural integrity under the immense load of the Burj Khalifa. Concrete Quality: High-strength concrete was used to withstand the significant forces applied by the building and the environmental conditions. 5. Waterproofing Membranes and Coatings: Advanced waterproofing membranes and coatings were applied to protect the basement from groundwater infiltration. This was crucial given the high water table in Dubai. Drainage Systems: A comprehensive drainage system was installed to manage any water that might seep into the basement, further safeguarding the structure. #BurjKhalifa #DeepPiling #FoundationEngineering #SkyscraperConstruction #StructuralStability #HighRiseBuilding #AdvancedEngineering #BuildingTheFuture #ConstructionInnovation #MegaStructures

Understanding Structural Piles in Construction Structural piles are deep foundation elements that transfer structural loads to deeper, stable soil layers or rock, especially where surface soils are weak or compressible. Types of Piles: - End-bearing piles – Transfer load to hard strata. - Friction piles – Rely on skin friction along pile shaft. - Steel piles – High load capacity, often H or pipe sections. - Concrete piles – Precast or cast-in-situ, commonly used in buildings. - Timber piles – Suitable for light structures and temporary works. - Composite piles – Combine materials for specialized conditions. The main functions of piles are: support structural loads, resist vertical/lateral forces, minimize settlement and provide stability in challenging soil conditions. And how piles are driven? the popular method at least 4: - Driven piles: Installed using impact hammers or vibratory drivers. - Bored piles: Drilled and then filled with concrete (cast-in-situ). - Screw piles: Rotated into ground using torque. - Jack-driven: Pushed into the ground using hydraulic jacks (often in urban areas).

Most Foundations Fail Before Construction Even Starts (Because people guess the soil, but the soil doesn’t guess back) You can't fake ground strength And you can't fix a foundation mistake once the concrete sets That's why pile foundations exist → To transfer load far below where soft soil gives up → To anchor your structure into zones that actually resist Let’s dig into it ~ site-style ↓ What Is a Pile Foundation? Think of a pile as a deep anchor ↳ Driven into the earth ↳ Carries the structure’s load down to a stronger layer When surface soil can't handle the pressure → piles go deeper When you're building heavy → piles spread that stress smartly Common Types of Piles You’ll Work With ↳ End-Bearing Pile → Transfers load to a firm layer below → Picture it like pressing a column onto a concrete slab ↳ Friction Pile → No hard layer below? No problem → Load carried through skin friction with surrounding soil ↳ Steel Pile → Handles massive loads, resists bending, tough in harsh sites ↳ Timber Pile → Lightweight, affordable, but needs care to avoid decay ↳ Composite Pile → Hybrid materials ~ strength of steel, stability of concrete Installation Methods ~ Choosing What Fits the Site ↳ Driven Pile → Hammered in forcefully → Quick, but noisy ↳ Bored Pile → Drill first, pour concrete after → Ideal for tight spaces, vibration-sensitive zones ↳ Screw Pile → Twisted into the ground like a giant bolt → Fast, clean, minimal disruption ↳ Jacked Pile → Pressed into place hydraulically → Quiet and precise ~ perfect for retrofitting or sensitive foundations Why This Isn’t Just Theory I’ve seen piles that were perfect on paper But failed on-site because no one cross-checked the soil report I’ve also seen lean budget piles perform beautifully All because the team chose the method based on real ground data ~ not assumptions Foundation success is not just engineering It’s communication between geotech, structure, and site conditions Next time you see a bridge, tower, or even a pier standing still Know this → It’s not the concrete you’re looking at It’s the underlying calculation that got respected ↳ What pile method do you rely on most in your projects? Drop your lesson ~ help the next engineer avoid an expensive mistake P.S. Follow Md Asif Azad for more. #FoundationDesign #PileEngineering #GeotechnicalWisdom #MdAsifAzad #CivilEngineering #FieldReady #DeepFoundation #SoilMatters #StructuralBase #ConstructionExecution #SiteToStructure

cross sea bridge construction Constructing cross-sea bridges involves several methods, including building foundations using cofferdams or caissons, constructing piers, and then erecting the bridge deck, all while considering the unique challenges of the marine environment. Here's a more detailed breakdown: 1. Foundation Construction: Cofferdams: In shallow waters, a cofferdam, a temporary dam, can be built to enclose the area where the foundation will be laid, allowing the water to be pumped out and work to be done on a dry seabed. Caissons: For deeper waters, caissons, which are watertight chambers, can be sunk to the seabed, allowing construction of the foundation in a dry environment. Pile Foundations: In unstable seabeds, piles, long, strong columns, can be driven deep into the ground to provide a stable base for the piers. 2. Pier Construction: Underwater Piers: Once the foundation is in place, piers, the supporting columns of the bridge, are constructed. Construction Methods: These piers can be built using methods like prefabrication (constructing parts on land and then transporting them to the site) or in-situ concrete casting (pouring concrete directly into molds on the seabed). 3. Bridge Deck Construction: Superstructure: Once the piers are in place, the bridge deck, the road or rail surface, is constructed. Materials: Common materials for bridge decks include steel, concrete, and asphalt. Methods: The bridge deck can be assembled on land and then lifted into place, or built section by section on the piers. 4. Considerations for Cross-Sea Bridges: Environmental Factors: Cross-sea bridges are exposed to harsh marine conditions, including strong currents, waves, and storms, requiring robust designs and materials. Seismic Activity: Bridges in earthquake-prone areas need to be designed to withstand seismic forces. Navigation: The design of the bridge must ensure safe passage for ships and other marine traffic. Materials: The materials used in cross-sea bridges must be resistant to corrosion and other marine degradation. Construction Challenges: Building in the water can be challenging, requiring specialized equipment and techniques. Risk Management: Construction projects of this scale require thorough risk assessment and management to ensure safety and successful completion.

**Vibro Stone Columns ** It's a ground improvement technique used to enhance the load-bearing capacity and drainage properties of weak or compressible soils. This method involves inserting columns of coarse gravel or crushed stone into the ground using a vibrating probe, which compacts the surrounding soil and improves its strength. **Process of Installing Vibro Stone Columns:** 1. **Insertion of Vibro Probe** A vibrating probe is driven into the ground to the required depth, either by self-weight, vibration, or air/water jetting. 2. **Formation of the Column** Aggregate is poured into the hole and compacted in layers using the vibratory probe. This process continues until the column reaches the surface. 3. **Compaction of Surrounding Soil** The vibration not only compacts the stone but also densifies the surrounding soil, increasing its strength and reducing settlement. **Applications of Vibro Stone Columns: 1- Increasing Bearing Capacity: Used in weak soils like soft clays, silts, and loose sands. 2- Reducing Settlement: Helps minimize long-term settlement in foundations. 3- Improving Drainage. There are two main types of Vibro Stone Columns, and the choice between them depends on soil conditions, site constraints, and the execution method: 1. Wet Method – Using Water Jetting: - The vibro probe is driven to the required depth with the assistance of high-pressure water jetting. - Water helps to displace loose soil and create the required cavity for the stone aggregate. - This method is used in soft soils or when penetration is difficult with vibration alone. - Requires a proper drainage system to handle excess water and displaced soil. 2. Dry Method – Without Using Water: - The vibro probe is inserted directly into the soil using vibration and self-weight. - Stone aggregate is fed into the hole by gravity or through a feeding tube. - Used in unsaturated soils, such as sand or stiff clay. - Provides a cleaner work environment as there is no excess water to manage. *Choosing the Right Method: 1- The Wet Method is preferred when the soil is very weak and cannot support the sidewalls of the hole. 2-The Dry Method is suitable when the soil can sustain the hole’s sidewalls during installation. Both methods are effective in improving soil strength and load-bearing capacity, and the selection depends on soil properties and project requirements.