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1. What must be considered when designing a dewatering system?

As stated in our reading for this week, the planning of a successful dewatering operation requires the knowledge of the ground conditions to be dewatered. The essential information includes the sequence of soil strata to be encountered, their permeabilities, and the position of the natural groundwater table during the construction period. The amount of groundwater lowering required. The duration of the period of dewatering. Lastly, the applicability and costs of the various dewatering methods that may be employed.

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2. Under what conditions would a slurry wall system be very effective?

The slurry trench method has been successfully developed to deal with particularly troublesome dewatering and excavation support problems such as those encountered in structures and dams. Slurry walls often are used where the waste mass is too large for treatment and where soluble and mobile constituents pose an imminent threat to a source of drinking water.

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3. Under what conditions would a sinking caisson be effective?

This method has been used successfully for small structures only a few feet or meters in diameter and for large structures over 100 ft. in width. Usually very soft ground.

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D G

2. Under what conditions would a slurry wall system be very effective?

Slurry walls is a technique used to build reinforced concrete walls in areas of soft earth close to open water. This technique is used to build water-blocking walls that surround tunnels to lay foundations. These walls are used to contain contaminated groundwater and direvert uncontaminated groundwater flow; it provides a groundwater treatment system. If there are highly acidic or alkaline contaminants, they may not be compatible with the wall material.

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  3. Under what conditions would a sinking caisson be effective?

Caissons are prefabricated cylinders or hollow boxes that are sunk into a desired depth beneath oceans, rivers, and other waters of bodies. Then, they are filled with concrete to create a solid foundation serving as an anchor. South Padre Island has finally earned approval and has started building a pier. Bridge piers generally require a caisson. Steel reinforcement can be used as a portion if needed to provide a more stable structure. This helps distribute the weight. The strength of concrete design mix and concrete shaft cover play a vital role. The friction resistance to the soil can significantly increase or decrease the sinking process.

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4. Under what conditions might you want to use cofferdams?

Cofferdamns are essential when you have a project that requires dewatering. This method keeps the jobsite dry. These dams allow an enclosed area to pump out water so excavation can be done when the ground is dry. This method is used on bridge piers or any other structure to be built within water.

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HM

1. What must be considered when designing a dewatering system?

Dewatering is usually the contractor’s responsibility. The contractor must consider the safety operations of the design of a dewatering system. Soil type and groundwater control requirements are also important to consider when designing a dewatering system. The contractor is responsible for the design, construction, operation and maintenance, just to name a few that need to be kept in mind.

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2. Under what conditions would a slurry wall system be very effective?

A slurry trench method is successful when dealing with troublesome dewatering and excavation support problems. This method includes the construction of an impervious barrier beneath the ground surface. As excavation for the wall is in progress, the material removed is replaced with a heavy clay slurry. The slurry is enough to support the excavation walls. The slurry can also be collected and reused. These constructed barriers have proven effective in most foundation materials and have been constructed to depths exceeding 200 ft. Slurry walls are helpful because they are resistant to contamination of groundwater.

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3. Under what conditions would a sinking caisson be effective?

The caisson method is the excavation from within a permanent structure. The structure is built in place if the site is on land or floated into position is the site is located in water. The caisson method is successful for small structures that are only a few feet or meters in diameter and for large structures over 100ft in width. As long as air pressure within the caisson is greater than the water pressure at its base, the intrusion of water is prevented. However, the caisson method may not be successful in very soft ground since it could be difficult to maintain the alignment of the caisson during the excavation process.

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