As a Structure Management Expert of I-Consult Ltd appointed by I- Build Sdn Bhd, I am necessary to propose different types of retaining wall system available. My proposal targets the site investigation, importance of retaining wall, building methods, design ideas and preventive options to mitigate functional failures. I am required to propose an appropriate selection of the best option retaining wall system used to the Plank of Directors, where the project is located at hilly area which includes 20 items of luxury bungalows.
the need for site investigation,
the need for keeping wall,
the concept of retaining wall,
types of keeping wall
the the most suitable retaining wall because of this hilly task.
The Need for Site investigation
Every man-made civil anatomist structure is found on, in or with floor. The composition we put on the bottom is man-made. We can control to design every item that goes into our framework, such as concrete, reinforcement, bricks and even the last wall plug. However, the ground below on which this composition will stand is not man-made. We usually have less understanding of it and we certainly cannot design or control its tendencies. The ground below will determine the economies of how large, how heavy, how safe the ultimate structure is going to be rather than the other way round. In short, the safety and economics of each civil engineering structure is influenced by the properties of the bottom which this composition will stand. These properties of the bottom below or sub-soil properties are obtained via Site Exploration.
What type of investigation is needed,
Why these are needed,
Where the actual field works should be performed,
How the task is usually to be done.
Whether the exploration is sufficient or too much.
Site investigation is normally crucial and completed prior to the commencement of design of a development project. Site exploration has been defined as research of the physical characteristics of the website and includes documentary studies, site surveys and ground investigation. It is also refers to the genuine surface or subsurface inspection, including on site and laboratory tests. In extensive sense, study of the site background and environment, interpretation and analyses of most available data, and making tips on the beneficial/unfavorable locations, economic and safe design, and prediction of potential hazards should also be contained in site investigations.
First and most important, a desk research to disclose data which might already exist regarding the site, its geology and background, together with a site reconnaissance, is important and can be carried out before purchase at minimal cost. This may be followed by trial pitting, probing or boring as appropriate to the conditions unveiled by preceding studies and in the light of the development proposals. Additionally it is a precaution to minimize damage that could be induced by these soils may be communicated at this time. At least home dwellers would be alerted to potential problems (and the associated costs) from the outset, thus permitting them to make up to date decisions regarding the most appropriate basis system for his or her homes.
Site investigation was created to identify the characteristics of soils or load materials which lay beneath the site, the groundwater conditions and the presence and extent of other physical features or contaminants which might be present. This information influences the selection and design of an appropriate structural form for the suggested building. It really is a process that ought to keep on an iterative basis throughout the design and construction phases. Post-construction monitoring may also be of importance in many instances within a validation process.
The merged building tons indicated in shape 1 must be easily backed by the subsoil and also ensure that unreasonable movements of the building do not take place. In the event the supporting soil is sufficient resistant and its characteristics under weight will probably remain satisfactory, the issues of support and motion will be easily solved. However, few soils other than rock can resist these concentrated tons which is usually necessary to collect the solved loads at their least expensive point and transfer them to enough bearing soil regarded as available on a specific site (amount 2).
Figure 1: Merged building loads
Figure 2: Method of transferring merged building tons to supporting ground.
The general syndication of land types in britain is indicated in number 3; the soils include peat, clay, slit, sand and gravel. Corresponding safe bearing pressures are also given.
Figure 3: simplified syndication of varied types of promoting soils
Lastly, site inspection should be carried out by professional specialists, such as surveyors, geotechnical engineer and earth investigation contractor, and in a phased manner. The bottom investigation company is accountable for providing reliable factual data. The geotechnical advisor should accountable for the planning & execution of the analysis program, interpretation and analyses of results, and making appropriate design recommendations to avoid over design as well as unsafe design.
Failure of Site Investigation
Due to insufficient or inadequacy of guide/code necessity regarding the amount as well as quality of site investigation work, geotechnical failures often occurred. These failures sometime resulted in catastrophic disaster and imposed serious threat to public safeness.
(i) Developing unsuitable foundations;
(ii) Lack of care and concern of the hill and slope;
(iii) Issuing a notice to the regulators confirming the drainage works was completed when only a small percentage from it was done.
By the above mentioned acts of setting up, building and supervising the structure of Highland Towers and the drainage system of the Highland Towers site, he was negligent and possessed brought on nuisance to them. The civil engineer acquired used rail hemorrhoids welded collectively as foundation to support the three apartment blocks. This sort of piles, that was considered inferior to concrete hemorrhoids, was accepted in the executive and building industry to support high-rise structures at the materials time. Thus, no fault can be related to the civil engineer in using the rail piles as he was only adhering to the accepted professional practice in those days. However, there is lack of consideration by the civil engineer to the hill and the slope directly behind the three blocks. The court ruled that the civil engineer should have sensibly foreseen the danger of a landslide creating a lateral insert against the building blocks of the building. For this, he should have exercised care and attention to either design or construct a foundation to accommodate the lateral fill or ensure that the slope was realistically stable. Failure to take action is a breach of his responsibility of care he owes to the Plaintiffs since his obligation was to guarantee the security of the properties he designed and built. The civil engineer's try to deny liability on the ground that he relied on the programmer to ensure that other keeping walls were made properly was unsuccessful. The judge found that it was incumbent after the civil engineer to enquire and ascertain if the work was that of a professional professional and what its impact might be on the protection of his own building.
Figure 4: Highland Event in Kuala Lumpur in 1993
What is Retaining Wall?
A retaining wall is a stabilizing composition designed and built to retain soil at a slope that is greater than it would by natural means suppose, usually at a vertical or near-vertical position. Besides, the keeping wall used to avoid the erosion and the movements of land. The function of keeping wall is to resist the lateral pressure of land when there's a desired change in surface elevation that surpasses the natural slope considered by the soil which is called the angle of repose of the land. The retaining wall is the wedge of ground resting on this upper aircraft of the position of repose that a retaining wall has to support.
It is also made with weep holes which allow gathered water to flee. This releases the additional pressure created by way of a accumulated water and helps in stabilizing the keeping wall.
Figure 5: Terminology of Retaining Wall
Constructing a retaining wall, several types of materials can be utilized. Stone and concrete are the most common materials used in constructing a retaining wall. Besides, there are also special keeping wall blocks built from aggregate materials and light cement which are designed for this purpose. Because each stop fits firmly with another, some styles interconnect, making building simpler, less costly and time required. These blocks do not require the addition of mortar due to the fit of these blocks is secure.
A keeping wall can be tiers or a series of "steps", which allow more efficient erosion control and a more sophisticated design. Different types of plantings, blossoms or materials in each tier can be included in the design to bring more color, texture and interest to the area. By breaking down the amount of soil and pressure, a tiered design also give a better erosion control placed by each department of the retaining wall rather than adding the aesthetic value.
Today, there are several styles and types of keeping wall blocks, & most people choose preformed blocks. Unlike today, large stones and railroad ties were often used to construct a tiered retaining wall in the past. Performed blocks are affordable and consumer- friendly, making other methods out of date at all, except the appearance of rough natural stone or wood is preferred.
The Concept of Retaining Wall
Nature and kind of soil;
Height of water table;
Subsoil water moves;
Type of wall;
Materials used in the construction of the wall.
Coulomb's graphical representation or wedge theory.
ACTIVE Globe PRESSURE are those that have a tendency to move or overturn the keeping wall, and are composed of the planet earth wedge being maintained together with any hydrostatic pressure triggered by the existence of groundwater. The latter can be reduced through subsoil drainage behind the wall structure, or by inserting drainage openings called weep holes through the thickness of the stem, permitting the water to drain away.
PASSIVE Globe RESISTANCES are reactionary pressures that will behave by means of a amount of resistance to activity of the wall structure. If the wall membrane tends to move ahead, the earth in front of the toe to counteract the forward movements. This pressure can be increased by enlarging the depth of the toe or by forming a rib on the underside of the bottom.
Active earth stresses must equal to passive globe resistances to avoid overturning and round slip. Typical examples of these stresses are shown in physique 6 and number 7.
Figure 6: Active and Passive Earth Pressures take action on Mass Retaining Wall
Figure 7: Dynamic and Passive Globe Pressures take action on Cantilever Retaining Wall
EFFECT OF WATER
The design and stableness can be affected by ground normal water behind a retaining wall structure whether static or percolating through subsoil. The pressure on the rear of the wall will be increased. By minimizing the earth shear power, the bearing capacity of the dirt can be reduced; it can reduce the frictional resistance between the base and the dirt and reduce possible passive pressure in front of the wall. As a result, the problem of drainage of this particular behind the keeping wall is the utmost important in the look.
SLIP CIRCLE FAILURE
Slip circle failing (shown in shape 8) is sometimes encountered with keeping wall structure in clay soils, especially where there is a heavy surcharge of maintained material. It requires the form of a rotational motion of the dirt and wall along a round arc. The arc commences behind the wall membrane and passes under the base, producing a tilting and forward movements of the wall. Further motion can be avoided by driving sheet piles into ground before the toe, to a depth that will slice the slip circles arc.
Moment due to weight of retained earth and wall above slip circle arc about O is higher than restoring point in time RM.
RM=permissible shear stress x length of arc ABC x arc radius OC
Result: mass above ABC rotates about O. Wall tilts onward and earth heaves in the front.
Figure 8: Retaining wall failure due to rotational movement.
The Need for a Retaining Wall
A retaining wall structure might be built on property for various reasons. Some level of dirt and earth will be presented abroad, garden, pool or play area because they build a retaining wall.
The sheer aesthetics may also be added on it. A more usable land will be provided if there have a great deal of rolling and slopping yard.
Retaining Walls RESTRAIN the Earth
Buildings might be built over a hill or in a valley between several hills. Retaining wall will hold back the earth after the hillside has been dug out to create buildings. Dirt does back in from the sides of the wall structure with each shovel full. A lot more you shovel, the dirt begins to show up back. the attributes are loose and weakened, so they will crumble at the slightest provocation.
The mud which remains must discharge when the side of your hill is dug out. If remaining alone, it will eventually comes tumbling down. The dirt will be kept again and the safe practices will be ensured.
Retaining Wall space Provide More Useful Land
A walk-out basement, patio, playground, garden, rugby court or swimming pool might be installed into suggested development. In the event the land is rolling or hilly, work can't be begun before surface is leveled off.
A sort of cliff, where a area of the proposed land which is not dug out is greater than the lower smooth land, will then be overlooked. Adding a keeping wall will have more functional land as well as will add composition and beauty to your brand-new area. Retaining wall can be used as steps into the pool where pool equipments to be presented.
Retaining Surfaces Avoid the Ground from Cleansing Away
If the area gets a whole lot of rainfall or near normal water such as lake, a retaining wall will keep water from eroding the ground of your landscaping and around your foundation. This could be a safety solution to avoid landslides and river of dirt from floating into the buildings.
Types of Wall
Mass keeping walls
Mass retaining wall surfaces also known as gravity wall space. They rely after their own mass together with the friction on the lower of the bottom to conquer the trend to slide or overturn. They are usually economic only up to a height of just one 1. 800m. Mass wall surfaces can be constructed of semi-engineering quality bricks bedded in a 1:3 concrete mortar or of mass cement. Mass concrete could have some light fabric reinforcement to regulate surface cracking. Natural stone is suited to small surfaces up to 1 1. 000m high, but generally it is used as a facing material for walls up to at least one 1. 000m high, but generally it is utilized as a facing material for wall membrane over 1. 000m.
Figure 9: Brick Mass Retaining Walls
Figure 10: Mass Cement Retaining Wall with Rock Facings
Cantilever surfaces are usually of reinforced concrete, and focus on the rules of leverage. Two basic varieties can be considered: a base with a large heel so that the mass of the wall with a big toe (physique 10). The figure shows typical sections and patterns of reinforcement came across with these basic varieties of cantilever retaining wall structure. The main steel occurs on the strain face of the wall membrane, and nominal material (0. 15% of the cross-sectional section of the wall) is frequently included in the opposite face to regulate the shrinkage breaking that occurs in in-situ concrete work. Reinforcement requirements, bending, fabricating and placing are handled in detail in the section on the reinforced concrete.
Reinforced cantilever surfaces have an financial height range of 1. 200-6. 000m. Walls in excess of this elevation have been financially created using prestressing techniques. Any durable facing materials may be applied to the top to increase the appearance of the wall, but it must be appreciated that such surface finishes are decorative and add nothing at all to the structural power of the wall.
Figure 10: Reinforced Cement Cantilever Retaining Walls
Counterfort Retaining Walls
These wall surfaces can be made of reinforced or prestressed concrete, and are believed appropriate if the elevation is over 4. 500m. The counterforts are triangular beams put at ideal centres behind the stem and above the base to enable the stem and bottom part to do something as slabs spanning horizontally over or under the counterforts. Physique 11 and amount 12 show a typical section and routine of reinforcement for a counterofrt keeping wall.
If the counterforts are positioned on the face of the stem they are really termed buttresses, and the whole arrangement is named a buttress-retaining wall. The look and construction concepts are similar in both formats.
Figure 11: Reinforced Concrete Counterfort Retaining Wall
Figure 12: Reinforced Concrete Counterfort Retaining Wall
Reinforced masonry keeping walls
Steel reinforcement may be used in brick keeping walls to resist tensile forces also to prevent the ramifications of shear. A brick bonding set up known as Quetta relationship is used to make a uniform distribution of vertical voids. Vertical metal reinforcement is linked with the building blocks reinforcement and spaced to coincide with purpose-made voids. The voids are filled up with concrete to produce a group of reinforced concrete mini-columns within the wall when the brickwork is completed.
Where appearance is not important, or the wall structure is to get a surface treatment, reinforcement and in-situ concrete within hollow cement block work give economical and functional construction. Number 13 shows the application of standard-profile, hollow, dense concrete blocks place in stretcher bond as long term formwork to ongoing vertical columns.
Figure 13: Reinforced Concrete Block Retaining Wall
Quetta relationship with steel pubs concrete in the voids;
Stretcher-bonded extensive cavity with reinforced metallic bars coated for corrosion coverage;
Solid wall of perforated bricks with ongoing voids including grouted steel reinforcement pubs.
Figure 14: Post-tensioned Brick Retaining Walls
Based on dialogue shown on above, I'd like to select Cantilever retaining wall as the utmost suitable retaining wall for the project where is located at hilly area which contains 20 devices of luxury bungalows.
As shown as above, a cantilever retaining wall is a form of masonry installation that holds a large amount of earth in place. The cantilever design is just one of the variations on a retaining wall structure design, using various key points to manage globe loads. Cantilever retaining wall has an economic height selection of 1. 200-6. 000m. This type of retaining wall membrane is suitable for bungalows because the height is sufficient to support the bungalows.
A concrete cantilever retaining wall uses a relatively skinny stem of steel-reinforced, cast-in-place, concrete or mortared masonry. Inside a cantilever retaining wall design, an globe pressure vector acts horizontally against the medial side of the wall. The bottom part of the wall reveals a gravity vector downward. That gravity vector produces an other force upwards. The causing vector counters the earth pressure vector, and pushes back again against the earth load. This type of retaining wall membrane is more secure compared to the other three types which explained on above in order to create 20 items of luxury bungalows because the tons are distributed similarly.
Retaining wall membrane design is evaluated to moderate the effects of the landslide. Retaining walls can be helpful in protecting dirt against the sorts of motion associated with these natural disasters. Looking at landslide risk and the chance of liquefaction, the saturation of earth, is part of assessing how a retaining wall structure works. Cantilever retaining wall is the one which involves a uniform thickness wall membrane which is linked with a footing. It located at the basement of bungalows. Thus, cantilever keeping wall will hold back the earth. Land erosion, landslides and environment disasters are less likely to be occurred. In other words, breaking and collapse of 20 units of luxury bungalows are avoided.
Weep holes were created in the cantilever keeping wall release a the additional pressure created by way of a accumulated water and helps in stabilizing the retaining wall. This ensures the building won't collapse due to the fast circulation of normal water on the hill.
In conclusion, a suitable retaining wall can stabilize the ground and steer clear of overturning and sliding of building. Beside, a suitable retaining wall membrane can also help in saving the structure cost. Therefore, cantilever keeping wall is the most suitable retaining wall structure for 20 products of luxury bungalows which are located on the hilly area.
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