During the sinking phase of well foundations, shifting and tilting can occur and may result in serious problems that can weaken the stability of the foundations. To avoid these issues, proper precautions must be taken. These precautions include carefully monitoring the sinking process and ensuring that the foundation is properly aligned. Limitations must also be considered, as the amount of weight and pressure that a foundation can support is limited. If the foundation is subjected to excessive weight or pressure, it may shift or tilt. In the event that shifting or tilting does occur, there are several rectifying methods that can be employed. These methods include using jacks to lift and level the foundation, adding additional support to the foundation, and adjusting the alignment of the foundation.
Shifting and Tilting of Well Foundations
The given context refers to two terms associated with the positioning of a well foundation. The first term, shifting of the well foundation, is used to describe a situation where the well is moved horizontally away from its desired position. This can occur for a variety of reasons, such as changes in the geological conditions or errors in the placement of the foundation.
The second term, tilting of the well foundation, is used to describe a situation where the well is sloped against its vertical alignment. This can also occur for various reasons, such as uneven settling of the foundation or changes in the surrounding soil conditions. Both of these situations can be problematic for the stability and functionality of the well, and may require corrective measures to be taken in order to ensure proper performance.
Precautions to Prevent Shifting and Tilting
To prevent shifting and tilting of well foundations, several safety measures should be considered. One such measure is to ensure that the diameter of the well curb is larger than the external diameter of the steining. Experts generally recommend a difference of 40 to 80 mm. Additionally, it is crucial to ensure that the well steining is symmetrically placed over the curb. This symmetry is essential to maintain the stability of the foundation.
The outer surface of both the well curb and the steining should be smooth. Any roughness or unevenness on the surface can lead to instability and cause the foundation to shift or tilt. Moreover, it is vital to uniformly dredge all the sides of the well foundation. This uniform dredging ensures that there is an even distribution of the weight across the foundation.
Lastly, the cutting edge of the foundation should be uniformly thick and sharp. This sharpness is crucial for the foundation to penetrate the soil and gain support. By following these safety measures, the well foundation can maintain its stability and prevent any potential damage or accidents.
Limitations
Well foundation is a type of foundation used in civil engineering, which is subjected to various loads and forces. It is essential to maintain the stability and integrity of well foundation to ensure the safety of the structure built upon it. To ensure the stability of well foundation, certain limits have been set.
One such limit is the maximum tilt allowed in case of well foundation, which is 1 in 60. This means that the angle of deviation from the vertical axis should not exceed 1 unit for every 60 units of length. If the tilt exceeds this limit, it can be considered dangerous and may require remedial measures.
Another limit that needs to be considered is the shift in well foundation, which should not be more than 1% of the depth of sunk. If the shift exceeds this limit, it can also be considered dangerous and may require remedial measures.
In cases where the well foundation exceeds the above limits, it is considered dangerous, and steps must be taken to rectify the shifting and tilting. Remedial measures may include reinforcing the foundation or reducing the load on it. It is important to take appropriate measures to rectify the issue to prevent any potential harm to the structure or people using it.
Rectifying Methods
Rectifying shifting and tilting problems in well foundations can be accomplished through several methods. One such method is eccentric loading, which involves loading the foundation in a way that compensates for the shift or tilt. Another method is excavation on the higher side, which involves removing soil from the higher side of the foundation to restore balance.
Water jetting is another option for rectifying well foundation problems. This method involves using high-pressure water jets to remove soil from around the foundation and reposition it into the correct alignment. Alternatively, pulling the well may be necessary, which involves using equipment to physically pull the foundation back into place.
Hydraulic jacks can also be utilized to rectify shifting and tilting issues in well foundations. By placing the jacks strategically and applying pressure, the foundation can be adjusted to the correct alignment. Struts can also be used in combination with hydraulic jacks to provide additional support and stability.
Excavation under the cutting edge of the foundation may also be necessary to rectify shifting and tilting issues. This method involves removing soil from under the edge of the foundation to level it out. Additionally, placing wood sleepers under the cutting edge can provide support and help prevent further shifting or tilting.
1. Eccentric loading
To rectify the tilt of a well, one common method is to apply eccentric loading on the higher side. The higher side refers to the opposite side of the tilt or the lower side of the well. This is achieved by constructing a loading platform on the higher side and placing a load on it. The eccentric load applied to the higher side increases the downward pressure, which then helps to correct the tilt.
The amount of load and eccentricity needed for correction is determined by the depth of sinking of the well. The greater the depth of sinking, the larger the eccentricity and load required. By using this method, the tilt of the well can be corrected, and the well can be restored to its proper vertical position.
2. Excavation on Higher Side
When sinking a well, it is not uncommon for the well to become tilted to one side. When this happens, a technique that can be used is to increase the excavation on the opposite side of the tilt. This approach helps to correct the tilt and ensure that the well remains straight.
However, it is important to note that this technique is most effective when used in the initial stages of well sinking. As the well becomes deeper, it can become increasingly difficult to correct any tilting, and more advanced techniques may need to be employed to keep the well on track.
Overall, while the technique of increasing excavation on the opposite side of a tilt can be helpful in the early stages of well sinking, it is not a solution that can be relied on throughout the entire process. Careful monitoring and adjustments may be necessary to ensure the well remains straight and functions effectively.
3. Water Jetting
Water jetting can be used as a remedial measure to correct the tilt of a well. By directing a forceful stream of water towards the external surface of the well on the higher side, the friction between the soil and the well surface can be reduced. This reduction in friction can cause the higher side of the well to become lowered, which ultimately helps to make the well vertical.
Overall, water jetting can be a helpful technique for correcting the tilt of a well by decreasing the amount of friction between the well surface and surrounding soil.
4. Pulling the Well
It is possible to pull a well towards the higher side by using steel ropes. To do this, one or more steel ropes are wrapped around the well, and wooden sleepers are placed in between the well and ropes. This is to ensure that the well’s steining is not damaged and that the load is distributed over a larger area of the steining. It is essential to perform the pulling process with caution to avoid any potential shifting of the well’s foundation, which could result in severe damage.
5. Pushing using Jacks
One way to address the tilting and shifting of a well foundation is to use hydraulic or mechanical jacks. By pushing the well from the lower side to the higher side, the tilt can be corrected. To ensure the stability of the jack system, neighboring vertical well foundations or other suitable arrangements can provide support.
However, it is crucial to exercise caution when using the jack system to push the well. Improper handling may cause the well to shift, leading to further damage or instability. Therefore, careful monitoring and precision are necessary to avoid such complications.
6. Using Struts
To prevent further tilting of a well, struts can be used as supports on either the lower or tilted side. These struts are placed between the well steining and wooden sleepers in order to distribute pressure over a larger area and prevent damage to the well steining. The struts are also supported by a firm base, which has driven piles to provide additional stability. By using this method, the well can be reinforced and its structure can be maintained over time.
7. Excavation under Cutting Edge
The method described is specifically used for hard strata soils. Typically, the process involves de-watering the well and conducting an open excavation directly under the cutting edge located on the higher side. However, in cases where de-watering is not feasible, professional divers utilize appropriate equipment to loosen the soil strata. This loosening process allows for excavation to take place safely and effectively. It is important to note that this technique is only recommended for hard strata soils and should be carried out by trained professionals with the necessary equipment and safety precautions in place.
8. Wood Sleeper under Cutting Edge
The given context describes a situation where there is an increasing tilt towards the lower side. To control this tilting temporarily, wooden sleepers are placed under the cutting edge on the lower side. These sleepers act as a support to counter the tilt and maintain stability. Once the well is corrected to a vertical level, these sleepers can be removed.
In essence, the use of wooden sleepers serves as a temporary solution to manage the tilting and maintain stability in the well. This method is practical and cost-effective, as it allows for a quick response to the problem without the need for permanent modifications to the well structure. Removing the sleepers once the problem is resolved is a simple process, which allows for the well to return to its original state. Overall, this approach is an effective way to manage tilting in a well, ensuring its stability and safety.
Fig 7: Wood Sleeper under Cutting Edge