PILE FOUNDATION FAILURES AND THEIR REMEDIES

This article is about PILE FOUNDATION FAILURES AND THEIR REMEDIES

Pile foundations are a popular choice for constructing deep foundations in areas with challenging geological conditions and varying load requirements, particularly in the case of soft soil foundations. Compared to other types of foundations, pile foundations have a higher bearing capacity, better stability, and lower differential settlement. However, pile foundations are not immune to damage and failure, particularly during seismic events such as earthquakes.

Fig: Pile foundation failure

The failure of a pile foundation can occur due to various factors such as lack of adequate boring, inaccurate soil classification, improper size of hammer, misinterpretation of load, and vibration causing lateral or vertical movement. Other factors such as tension failure of concrete pile, decay due to lower groundwater level, and disintegration of concrete due to poor quality of concrete or reactive aggregate can also contribute to the failure of a pile foundation.

In addition, soft strata under the tip of the pile, damaged or buckling piles, and eccentricity due to bowing or falling out of plumb can also cause pile foundation failure. Factors such as insect and marine borer attack, corrosion, and collapse of the thin shell of the piles can also lead to the failure of a pile foundation. Overweight due to earthfill and flowing strata caused by adjacent excavation or bank sloughing can also contribute to the failure of a pile foundation.

To prevent the failure of a pile foundation, it is essential to undertake early repair such as encasement or replacement. Removing partial load and underpinning can also be effective remedies to prevent pile foundation failure. Proper boring, accurate soil classification, and correct driving formulas can also be useful in preventing pile foundation failure. It is also essential to ensure the appropriate size of the hammer, use of reinforcement in concrete piles, and proper maintenance of the pile foundation to prevent decay and insect attack.

Pile Foundation Problems and Solutions

Pile foundations are used to transfer the load of a structure to a deeper, more competent soil or rock stratum. However, they can encounter problems such as inadequate bearing capacity, settlement, and lateral displacement, which can compromise the stability and safety of the structure. Here are some common pile foundation problems and solutions:

Inadequate bearing capacity: This occurs when the load-carrying capacity of the pile is insufficient to support the structure. To solve this problem, the pile can be redesigned to increase its diameter, length, or number. Another solution is to use a different type of pile, such as a driven pile instead of a bored pile.
Settlement: Pile foundations can experience settlement due to the consolidation of the surrounding soil. To mitigate this problem, the pile can be designed to penetrate deeper into the soil or to be installed at an angle. Additionally, preloading the soil before construction can accelerate the consolidation process and reduce future settlement.
Lateral displacement: This happens when the soil around the pile undergoes horizontal movement, causing the pile to tilt or lean. One solution is to increase the lateral capacity of the pile by adding more reinforcing steel or using a larger diameter pile. Another solution is to install a soil nail or tieback to provide additional lateral support.
Corrosion: Piles made of steel are prone to corrosion in environments with high moisture or salt content. To prevent corrosion, the pile can be coated with a protective layer or made of a non-corrosive material such as concrete or fiberglass.
Pile damage: Piles can be damaged during installation or due to external forces such as earthquakes or soil movements. To prevent damage, the pile can be reinforced with additional steel or installed using a different method, such as driving instead of boring. Damaged piles should be repaired or replaced to maintain the stability of the foundation.

Overall, proper design, installation, and maintenance of pile foundations are critical to avoid problems and ensure the stability and safety of the structure they support. It is important to consult with a qualified geotechnical engineer to determine the appropriate pile type, size, and spacing for a given soil and loading condition.

Disadvantages of Pile Foundation

Following are disadvantages of pile foundation.

Cost: Pile foundations can be more expensive than other types of foundations due to the materials and equipment required for their installation.
Limited vertical capacity: Pile foundations can have limited vertical capacity in certain soil types, such as soft or loose soils. This can require the use of more piles, which increases the cost and complexity of the foundation system.
Difficult to inspect: It can be difficult to inspect the condition of piles once they are installed, which can make it challenging to detect problems such as corrosion or damage.
Noise and vibration: The installation of pile foundations can generate significant noise and vibration, which can be disruptive to nearby residents or sensitive equipment.
Site constraints: The installation of pile foundations requires access to the site by heavy equipment, which can be difficult in urban or densely populated areas. Additionally, the presence of underground utilities or other obstructions can limit the use of pile foundations.

Problem in Bored Pile Construction

Bored pile construction can encounter various problems during the drilling, reinforcement, and concreting phases. Here are some common problems in bored pile construction:

Collapse of borehole: Bored piles are drilled by excavating soil from the ground and replacing it with concrete. If the borehole collapses due to unstable soil conditions, it can result in a reduction in pile diameter or even the loss of the entire borehole. This can be avoided by using casing to stabilize the borehole, or by drilling with a bentonite or polymer mud to maintain the stability of the borehole walls.
Formation of necking: Necking occurs when the borehole diameter decreases at a certain depth due to the resistance of the soil or rock. This can result in a reduction of the pile’s cross-sectional area and capacity, which can compromise the pile’s performance. Necking can be minimized by adjusting the drilling parameters, such as the drilling speed or torque, or by using a larger diameter drill bit to reduce the resistance.
Inadequate concrete cover: The concrete cover of the reinforcement is critical to protect the steel from corrosion and ensure the durability of the pile. If the concrete cover is inadequate, the reinforcement can be exposed to corrosive agents or damage, which can compromise the pile’s structural integrity. This can be avoided by using proper reinforcement spacing and cover, and by ensuring that the reinforcement is properly secured in the pile during the concreting phase.
Excessive concrete slurry: During the concreting phase, excess concrete slurry can accumulate at the bottom of the borehole, which can lead to a reduction in the pile’s ultimate bearing capacity. This can be avoided by controlling the amount of concrete slurry and by ensuring that the concrete is properly placed and compacted.
Difficulties in removing the drilling tool: After the drilling is complete, the drilling tool can become stuck in the borehole due to the adhesion of the soil or rock. This can delay the construction process and increase costs. This can be avoided by using proper drilling techniques and equipment, and by lubricating the drilling tool to reduce friction. If the tool becomes stuck, it may need to be extracted with a specialized tool or technique.

Collapse of Soil in Pile Borehole

The collapse of soil in a pile borehole is a common problem encountered in the construction of bored piles. It can occur due to a variety of factors, including the instability of the surrounding soil, the presence of groundwater, or inadequate drilling techniques. Here are some possible causes and solutions for the collapse of soil in a pile borehole:

Instability of soil: The collapse of soil can occur due to the instability of the soil around the borehole. This can happen when the soil is too loose, too wet, or has low cohesion. To prevent this, the borehole can be stabilized by using casing or drilling fluid to support the borehole walls during the drilling process.
Groundwater: The presence of groundwater can cause the soil in the borehole to become unstable and collapse. This can be mitigated by using a drilling fluid that has a higher density than the groundwater, such as bentonite or polymer mud, to create a stable hydrostatic pressure and prevent the inflow of groundwater.
Inadequate drilling techniques: The collapse of soil can also occur due to inadequate drilling techniques, such as using a drill bit that is too small or drilling at an improper angle. This can be avoided by using appropriate drilling equipment and techniques, and by monitoring the drilling parameters, such as the drilling speed, torque, and pressure.
Remedial measures: If soil collapse occurs during the drilling process, remedial measures can be taken, such as filling the borehole with drilling fluid or grout to stabilize the soil and prevent further collapse. In some cases, it may be necessary to abandon the borehole and start over.

Overall, preventing soil collapse in a pile borehole requires careful planning, proper drilling techniques, and effective monitoring. It is important to consult with a qualified geotechnical engineer to determine the appropriate drilling methods and materials for the specific soil and groundwater conditions at the site.

Pile Deviation Solution

Pile deviation refers to the horizontal displacement or misalignment of a pile from its intended location or orientation. Pile deviation can occur during the installation process due to a variety of factors, such as soil conditions, equipment malfunction, or operator error. Here are some possible solutions for pile deviation:

Monitoring: One of the best ways to prevent pile deviation is to monitor the installation process in real-time. This can be achieved by using instruments such as inclinometers or strain gauges to measure the vertical and horizontal position of the pile during installation. The data can be used to adjust the drilling equipment or correct any deviations that occur.
Realignment: If a pile deviates during installation, it may be possible to realign it by adjusting the drilling equipment or using specialized tools such as jacks or hydraulic rams to shift the pile back into position.
Abandonment: In some cases, it may be necessary to abandon a pile that has deviated too far from its intended location or orientation. The abandoned pile can be replaced with a new pile that is installed correctly.
Correction: If the pile deviation is minor, it may be possible to correct it by applying a lateral load to the pile in the opposite direction of the deviation. This can be achieved by using a hydraulic jack or other specialized equipment to shift the pile back into its intended position.
Redesign: If pile deviation is a recurrent problem, it may be necessary to redesign the foundation system to better accommodate the soil conditions and installation techniques at the site. This can involve changing the pile type, spacing, or orientation to improve the stability and performance of the foundation.

Common Pile Driving Problems and Solutions

Pile driving is a common technique used to install piles into the ground to support structures such as buildings, bridges, and offshore platforms. However, there can be several problems encountered during the pile driving process. Here are some common pile driving problems and their solutions:

Pile damage: Pile damage can occur during the driving process due to excessive bending, cracking, or splitting. To prevent pile damage, it is important to choose the right type of pile for the soil conditions and use the appropriate driving techniques and equipment.
Soil resistance: The resistance of the soil can affect the pile driving process. If the soil is too hard or dense, the pile may not be driven to the desired depth or may require excessive force. If the soil is too soft or loose, the pile may not be able to support the intended load. To overcome soil resistance, it may be necessary to use specialized equipment, such as vibratory hammers or impact hammers with higher energy, to increase the efficiency of the driving process.
Pile alignment: Proper alignment is crucial for the effectiveness of the pile foundation system. Deviations in the pile alignment can cause excessive stress or settlement of the structure. To prevent pile alignment issues, it is important to use accurate surveying and monitoring techniques during installation and to use specialized equipment, such as pile shoes or pile guides, to ensure that the pile remains in the correct position during driving.
Environmental concerns: Pile driving can cause environmental concerns, such as noise pollution and disturbance to aquatic life in marine environments. To mitigate these issues, it is important to use environmentally-friendly techniques, such as noise barriers or bubble curtains, to reduce the impact of pile driving on the surrounding environment.
Material quality: The quality of the pile material can affect the performance and longevity of the foundation system. Poor quality or defective piles can result in reduced load capacity or premature failure. To ensure the quality of the piles, it is important to use reputable suppliers and conduct regular quality control checks on the materials.

Overall, preventing pile driving problems requires careful planning, proper equipment, and effective monitoring. It is important to consult with a qualified geotechnical engineer and pile installation specialist to ensure that the foundation system is designed and installed correctly to minimize the risk of problems during and after the installation process.

Pile Verticality Check

Pile verticality check is a critical step in the pile installation process to ensure that the pile is installed vertically and meets the design requirements. Here are some common methods used for pile verticality check:

Plumb bob method: This method involves suspending a plumb bob from the top of the pile to check its verticality. A plumb bob is a weight attached to a string, and when the string is suspended from the top of the pile, it indicates the true vertical alignment. Any deviation from the vertical can be measured by comparing the position of the plumb bob to a reference point. This method is simple and easy to use, but it requires a clear line of sight and may be affected by wind or other external factors.
Spirit level method: This method involves using a spirit level to check the verticality of the pile. A spirit level is a tool that contains a bubble that indicates whether a surface is level or not. To use this method, a straight edge or a special bracket is attached to the pile, and the spirit level is placed on the bracket to check the pile’s vertical alignment. This method is more accurate than the plumb bob method and can be used in confined spaces, but it requires a level base to work effectively.
Laser level method: This method involves using a laser level to check the pile’s verticality. A laser level emits a laser beam that can be projected onto the pile, and any deviation from the vertical can be measured by comparing the position of the laser beam to a reference point. This method is highly accurate and can be used over long distances, but it requires specialized equipment and expertise.

Overall, the selection of the appropriate method for pile verticality check depends on various factors such as accessibility, accuracy, and cost. It is important to consult with a qualified geotechnical engineer or pile installation specialist to ensure that the correct method is selected and applied correctly to ensure that the pile is installed vertically and meets the design requirements.

Pile Eccentricity Rectification

Pile eccentricity refers to the deviation of the pile from its intended position or alignment. This can occur during the pile installation process due to various reasons such as soil conditions, equipment malfunction, or human error. Rectifying pile eccentricity is important to ensure that the pile can effectively support the structure and meet the design requirements. Here are some common methods used for pile eccentricity rectification:

Jacking method: This method involves using hydraulic jacks to push or pull the pile back into its intended position. The jacks are placed on the pile cap or adjacent piles, and the force is applied to the pile using a steel frame or a reaction beam. This method is effective for small to moderate pile eccentricities, but it requires specialized equipment and expertise.
Redriving method: This method involves removing the existing pile and redriving it into the ground at the correct position. This method is effective for large pile eccentricities and can ensure that the pile is installed vertically and meets the design requirements. However, it can be costly and time-consuming, and it may not be possible in certain site conditions.
Pile cap modification method: This method involves modifying the pile cap to accommodate the eccentricity of the pile. The pile cap can be extended or enlarged to provide additional support to the pile and compensate for the eccentricity. This method is effective for moderate to large pile eccentricities, but it requires careful analysis and design to ensure that the modified pile cap can effectively support the structure.

Overall, the selection of the appropriate method for pile eccentricity rectification depends on various factors such as the magnitude of the eccentricity, the site conditions, and the project requirements. It is important to consult with a qualified geotechnical engineer or pile installation specialist to ensure that the correct method is selected and applied correctly to rectify the pile eccentricity and ensure the safety and performance of the foundation system.

PILE FOUNDATION FAILURES AND THEIR REMEDIES