COSC 254

What additional steps are taken to prevent water entry?

A barrier type called dampproofing is applied to the basement walls.

What is filling?

A broad term that refers to the placing of any earth material.

What is a pressure-injected footing/compaction grouted footing?

A dry stiff mixture of concrete or grout is compacted into a pre-drilled hole.

How does an auger injected pile get formed?

A hollow stem auger is used to drill the hole, then concrete is deposited through the stem as the auger is withdrawn.

What is a drainage mat?

A manufactured sheet type material that is made of a plastic egg-crate-like structure. Or some other very open, porous material that is faced on the outside with filter paper that resists the soil particles and allows water to pass easily. Soil passage must be restricted so that drainage pipes do not get clogged.

What is Dampprooofing?

A moisture resistant cement plaster or asphalt compund that is applied in spray, troweled, or applied with a roller.

If a steel shell is to remain, what is done to it to give it additional strength?

A shell may be corrugated to increase its strength.

What is integral waterproofing?

A variety of ingredients that are added to to the concrete when mixing. These materials stop up the pores in the concrete and render it waterproof.

What is a mud slab?

A weak concrete slab used to create a temporary, level, dry base over an irregular, often wet excavation.

CLSM may be made weak and strong depending on the requirement. When is it made weaker than normal?

Around utility pipe excavation. This is done so it can be dug out by hand if needed.

Concrete is rarely adequate for this purpose?

As a water proofing. Water migrates through its microscopic pores, or through pathways created by: shrinkage cracks, tie holes, utility penetrations, or cold joints.

Disadvantage of fully adhered membrane sheeting.

Because of shear pressure fully adhered sheets are vulnerable to stress cracking and tearing.

How are sitecast concrete piles installed?

By driving a hollow steel shell into the ground then filling the shell with concrete.

Bearing capacity of a precast concrete piles?

Can range up to 500 tons.

What is Radon?

Cancer causing gas that occurs naturally within soils in concentrations that vary by region.

Look over figures on pages 74 & 75

Do it you punk!

How does drainage resist groundwater entry?

Draws water away from the foundation therefore reducing the volume and pressure acting on the wallas and slabs.

Where substructures enclose basements, parking garages, or other usable space, what must be kept out?

Groundwater

What is the function of a retaining wall?

Holds back soil where an abrupt change in elevation occurs.

What are the possible downsides to liquid applied membrane waterproofing?

However irregularities in thickness and curing can cause the system be inconsistent.

How is CLSM delivered to the site?

In concrete mixer trucks.

What is an active sub-slab depressurization system?

Installing a small electric fan to the passive vent. This fan extracts the gas from the soil and decreases the risks.

What happens to the steel shell after the concrete pile is formed?

It can remain or be removed and reused.

How is asphalt (aka bituminous) dampproofing applied?

It is a black liquid that is applied with sprayer or rolled on.

How is a cement plaster damppfroofing (aka parge coating) applied?

It is a light gray color and is troweled on.

What is a rammed aggregate pier?

Pre-drilled holes are filled with compacted crushed rock or stone. Very similar to soil mixing.

What must the retaining wall resist?

Pressures of soil and groundwater from the uphill side.

See Figure 2.65 for retaining wall figures

See figure 2.65

What is the advantage of a pressure-injected footing/compaction grouted footing?

Similar to soil mixing this process densifies and strengthens the surrounding concrete.

Which material is most commonly used to construct retaining walls?

Site-cast concrete

Why do perforations face downward?

So that as water levels rise, water enters the pipes at the lowest possible levels.

What is earth reinforcing?

Soil that is sandwiched between strips or meshes of galvanized steel, polymer fabric, or glass fibers. These systems stablilize the soil in the same manner that roots hold a plant in the ground.

What does drainage typically consist of?

Some combination of pourous backfill material: such as sorted gravel, drainage mat, or perforated drain pipe.

What happens once membranes pass testing?

Membranes are covered with protection board, drainage mat, or insulation board to protect from the sunlight or physical damage from backfilling.

Where is electro-osmotic waterproofing most commonly used?

Most commonly used to remediate leakage in existing foundations where other methods are impractical.

What do CLSM's make?

Mud Slabs

How does bentonite waterproofing work?

Once water comes into contact with the clay it swells and forms a barrier that is impervious to water passage.

What shapes (in section) do precast concrete piles come in?

Square, octagonal, or round

What is a deadman (retaining wall member)?

The deadmen in the horizontal timber wall are timbers embedded in the soil behind the wall and connected to it with timbers inserted into the wall at right angles.

How is sheet membrane waterproofing material applied?

The factory manufactured sheets are either adhered fully to the walls or allowed to lay loosely against it.

What is perforated drain piping?

Piping that is laid around the outside perimeter of the building foundation. Made of 4"-6" pipe with several parallel rows of perforations that let water enter.

How long are waterproofing systems expected to last?

The lifetime of the building. This is why they are inspected so carefully.

What is backfilling?

The replacement of soil materials to restore excavation back to its finished level.

What is the typical configuration of a base isolator?

They come in different forms, but one in particular consists of a multilayer sandwich of rubber and steel plates. As well as a lead core that dampens movement and keeps the layers together.

Are most precast concrete piles prestressed?

Yes, but sometimes for smaller buildings conventionally reinforced concrete precast piles are used.

Where are geotextiles?

geotextiles rae fabrics made of chemically inert plastics that are resistant to deterioration in soil.

What is the load capacity for sitecast concrete piles?

load capacity can range to 200 tons.

What does a passive radon control system consist of?

-A layer of gravel or another type of gas permeable materal -Over the gravel a plastic sheet membrane that is impermeable is placed -Slab is poured on top of the plastic membrane. All cracks and pentrations are sealed. -A vent pipe to the surface is ran from the gravel

What method is used to insulate basements?

-Attached directly to the wall -inserted in between furring strips -or a separately framed wall built to the inside of the wall

What are alternatives to a retaining wall?

-Earth Reinforcing -Gaibbons

Methods of underpinning (mentioned in text)?

-Foundation enlarged so that their is more soil to distribute to -made deeper so that it reaches to better stratum -Or the soil can strengthened either chemically or with grout. -minipiles can be inserted

How is compaction performed?

-Heavy rolling -vibrating -ramming

What must the design of the foundation wall take into account?

-Height of the wall -Pressures acting on the wall -Character the soil on which the wall will rest

What are reasons for underpinning?

-Improper design -Building size/load changes -New buildings or nearby construction disturbs existing foundation

What materials are retaining walls made of

-Masonry -Preservative treated wood -coated steel -precast concrete -sitecast concrete

What material is used to insulate basement?

-Polystyrene foam, glass or mineral fiber insulation boards (adhered with adhesives or fasteners or placed against wall) -Insualtion may be integrated into the concrete using insulating forms or in the cores of CMU

Advantages of precast concrete piles?

-high load capacity -freedom from corrosion or decay

Waterproofing is

-more expensive that dampproofing -therefore it is used where groundwater conditions are severe and subgrade space must be kept dry.

What materials is waterproofing membranes made of?

-plastic -asphalt compounds -synthetic rubbers -and other materials

What are some uses of geotextile fabrics?

-soil reinforcing -soil retention -drainage mat -erosion protection -under pavers on a terrace -weed control in flowerbeds

Stages and method of up-down construction?

1. Installation of perimeter slurry wall 2. Internal steel columns for the substructure are lowered into slurry filled holes. Concrete footings are tremmied beneath them. 3. Ground floor slab is formed and cured. 4. Now superstructure and substructure are constructed simultaneously. This is done by using mining techniques. 5. Each level of foundation is erected by excavating the soil below and laying a mud slab or CLSM then reinforcing and concrete is poured. Once cured the workers continue to work downward until foundation is complete.

There are three failure mechanisms in retaining walls mentioned in figure 2.64. See figure 2.64

1. Overturning 2. Sliding 3. Undermining (directly attributable to groundwater running beneath the wall)

What are the sizes of typical concrete piles?

10-30 inches in diameter

How does waterproofing resist groundwater entry?

Acts as a barrier to to the passage of water.

If the passive radon control system fails, what can be done?

Adding an active sub-slab depressurization system.

Advantages and disadvantages of sheet membrane waterproofing?

Advantages: Consist in thickness Disadvantages: Have seams, can't configure around difficult shapes.

What are minipiles?

Aka pin piles or micropiles. Made from a steel pipe or bar that is rammed into the ground then grouted in place.

How can up-down construction be economical?

Although its upfront cost can be more it can save significant construction time.

What is electro-osmotic waterproofing?

An electrical current is induced in a wall that forces the water to the outside of the foundation.

What is blind-side waterproofing?

Applied before the concrete is poured. Drainage mat is applied to the excavation sheeting, and other waterproofing is applied to the drainage mat. The concrete wall is poured against the membrane.

Where does backfilling occur?

Around foundations, substructures, and uttility pipes.

Where are waterstops placed?

Cold Joints

Who generally decides what type of waterproofing membrane to use?

Consultants from the trade who have specialized knowledge of these systems generally help decide what is the best method and material.

What is CLSM?

Controlled Low-strength Material is a backfilling material made of portland cement, fly ash, sand, and water.

What are gabions?

Corrosion resistant wire baskets are filled with cobble or boulder size rocks. The baskets are then stacked to to form retaining walls or slope protection.

In residential construction what must be done before the foundation is backfilled?

First floor structure must be complete b/c this braces the foundation walls laterally.

What is another name for CLSM?

Flowable Fill.

How is backfilling placed?

It is placed in layers called "lifts." These lifts are 4" to 1' in thickness. Each lift is compacted before the next is placed.

How is water different that dampproofing?

It is resists water passage even in the more demanding conditions of hydrostatic pressure.

What is underpinning?

It is the strengthening and stabilizing of an existing foundation.

What does a base isolator do?

It is used for building in areas with high seismic activity. When subjected to lateral forces the rubber flexes or yields and the isolator deforms. This keeps the shear pressure on the building from cracking the structure.

What is bentonite waterproofing?

Made from sodium bentonite (naturally occurring clay) that is highly expansive. bentonite is sandwiched between corrugated cardboard, geotextile fabric, or plastic and comes in sheets.

How long can substructure construction take?

Many months, or on very complex projects a year or more.

What is the method of applying liquid-applied membrane waterproofing?

Material is applied with spray or roller, and are seamless and can form around intricate shapes.

What is a waterstop?

Materials such as: plastic, metal, synthetic rubber, or materials that swell are placed where concrete mating occurs. These are vulnerable spots for water to enter.

How does radon affect buildings?

This gas seeps into the building through unsealed penetrations and cracks. It can endanger the occupants of the building.

What is Flood Tested?

This technique tests horizontal membranes by submerging them for an extended period of time in water.

Why do some large sizes of precast concrete piles have open cores?

To allow for inspection after driving.

Why are soil mixing and rammed/compacted aggregate piers used?

To allow for more shallow foundations to be built on top of them.

Why must precast concrete piles be handled carefully?

To avoid bending and cracking before installation.

Why are basements thermally insulated?

To prevent heat loss. This makes them more energy efficient and maintains occupant comfort.

What is the added cost of adding a passive radon control system during construction?

Very minimal

Disadvantage of loosely laid sheet membrane material?

Water can get under sheet material and it can be difficult to determine where exactly a leak has occurred.

Once water enters the perforated drainage pipe where does it go?

Water may flow by gravity to daylight on a lower surface elevation on a sloping site, a municipal storm sewer system, or a sump pit which is automatically pumped dry once full.

Two basic methods of resisting water?

Waterproofing and drainage.

What should the moisture content be of soil that is to be backfilled?

Wet enough to compact but not to wet that it becomes sloppy when compacting.

When would blind-side waterproofing be used?

When foundation encroaches on the property edge and workers cannot excavation cannot be enlarged to apply the waterproofing.

When would you put additional perforated pipes under basement slab?

Where groundwater levels are severe?

When are buildings constructed with a passive radon control system?

Where radon levels are high and infiltration needs to be minimized. In residential and educational bilding especially.

Can splices be made in precast concrete piles?

Yes with mechanical fastening devices that are cast into the ends of the piles.