Aggregate Piers:
The most economical method for ground improvement is aggregate piers. Before aggregate piers were used, engineers had to replace the weak soil with an engineering fill in order to use shallow foundations, but in some cases (load is very high) they had to use deep foundations, which is much more expensive. By using aggregate piers, we can now use shallow foundations in marginal soil without having to replace it. By using compacted aggregate to create stiff pier element, aggregate piers help to increase the bearing capacity, liquefaction resistance, shear strength, rate of consolidation and it reduces settlement.
There are two types of aggregate piers: Rammed Aggregate Piers and Vibrated Aggregate Piers (vibro stone columns).
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• Compaction is done in a rectangular or triangular pattern in a number of phases, each phase has a number of passes, it could be a primary pass, or secondary pass, …etc.
• For the spacing, a consideration should be done for the depth of compressible layer, permeability of soil and location of ground water table. As well as that when compacting for deeper layers a wider spacing should be used compared to upper layers.
Reference: http://nptel.ac.in/courses/105108075/module2/Lecture06.pdf
• Deep craters should be formed by tamping, and each crater should be filled with sand after each pass.
Reference: http://nptel.ac.in/courses/105108075/module2/Lecture06.pdf
Compaction grouting:
Also known as Low Mobility Grouting is a technique that improve the strength and stiffness of the soil by injecting low slump, low mobility aggregate grout into it. Since the grout can be injected in the side or at an inclined angle leading to beneath the building, the method can be used whenever the foundation of an existing building needs improvement. This technique can densify loose sands for liquefaction
of sand and gravel deposits that lay on top of London clay and it is
Seawalls: Good or Bad? Walter Cavanaugh and Gary Grossman have a serious dilemma. Their entire households were literally falling away from them. Their houses on Indio Drive in the Sunset Palisades Planning Area in Pismo Beach rest atop a bluff that protrudes into the sea.
The 1.78 mile western span of the bridge between San Francisco and Yerba Buena Island presented the first obstacle. The bay was up to 100 feet deep in some places and required a new foundation-laying technique. Engineers developed a type of foundation called a pneumatic caisson to support the western section. A series of concrete cylinders were grouped together and then capped-off, having the air pressure of each cylinder identical to balance the beginning of the structure. From there, the workers added sets of new cylinders until the caisson reached the bottom of the bay. Then, in order to reach the bedrock, they inserted long drills down the cylinders, digging until they reached bedrock. After the caisson was balanced at the bottom of the bay, workers filled it with 1 million cubic yards of concrete, more concrete than was used for the construction of the Empire State Building! This caisson connected the two suspension bridges that make up the western part of the bridge.
According to Suspension bridges: Concepts and various innovative techniques of structural evaluation, “During the past 200 years, suspension bridges have been at the forefront in all aspects of structural engineering” (“Suspension”). This statement shows that suspension bridges have been used for over 200 years, and that people are still using them today because they are structurally better bridges. This paper shows four arguments on the advantages of suspension bridges, and why you should use one when building a bridge. When deciding on building a suspension bridge, it has many advantages such as; its lightness, ability to span over a long distance, easy construction, cost effective, easy to maintain, less risk
From the top of the rock you can see gnamma pits. These are areas where the rock has weathered, leaving pits in the tock that soil builds into and plants hold it in
· The same diameter corer is used so to keep the surface area of each
[4] Muni Budhu. Soil Mechanics and Foundations 3rd Edition and Foundations and Earth Retaining Structures (Combined book made for UBC). John Wiley & Sons, Inc. 2011.
These types of bridges are either V-shaped or in an inclined position. An example of this type of bridge is the Albert Bridge in London, England. An additional type of bridge structure is the truss bridge. A truss bridge contains a pattern of diagonal columns that sit on top of the bridge. There are many types of designs, but the most common designs are the king posts, which consist of two diagonal columns supported by a vertical column, and queen posts, which consist of two diagonal columns supported by two vertical and horizontal columns near the peak. An example of a truss bridge is the Dom Luis I
An impact crater (impact basin or sometimes crater) is a circular depression on a surface, usually referring to a planet, moon, asteroid, or other celestial body, caused by a collision of a smaller body (meteorite) with the surface. In the center of craters on Earth a crater lake often accumulates, and a central island or peak (caused by rebounding crustal rock after the impact) is usually a prominent feature in the lake.
In these cases, such as building a reservoir, a huge number of concrete trucks are generally brought in in a caravan, and they pour their concrete into the forms that have been constructed onsite. In some cases, this order will put a concrete plant out of commission for a period of time due to the demand, and as such it must obviously be coordinated ahead of time.
What is a bridge? A bridge is a structure providing continuous passage over a body of water, roadway, or valley. Every bridge looks different from the another. Their bridge structure is different. There are nine types of main bridges. Bridge engineers use a lot of geometry to help them design the different bridges. Without geometry, the bridges would not be safe.
Geotechnical Engineering covers the engineering properties of soils, the fundamentals of soil mechanics, and the application of geotechnical data and fundamentals to the design of foundation elements, earth-retaining structures, excavations, earth embankments and highway pavements.
Soil mechanics studies are the most related studies in Geotechnical Engineering to geology. It is analyzing the site conditions and the soil properties. Many soil properties need to be checked like the Atterberg Limits, which is the shrinkage limit. This indicates how much would the soil shrink because of weather and water limits.