Retaining Wall Design - Essay Example

RЕTАINING WАLL DЕSIGN Name Institution Subject Instructor Date Retaining wall design overview Retaining walls are very significant when it comes to protection against erosion at the sites that are susceptible. This is due the major role played by the walls in soil retention. For the Retaining walls to be properly functional they need to be structurally stable, durable, and have a drainage provision. Appearance of the retaining wall design is also a very important consideration. Retaining walls are capable of offering the durability solution that is needed for a structure in contact with the earth and constantly exposed to wetting. Concrete used in the construction of retaining walls is expected to be resistant to both termites and rotting (Anderson, 2008). Important considerations in the design if retaining walls The first one of the considerations involves confirmation from the relevant authorities to obtain the necessary approvals. The other consideration that is equally important is the provision of detailed structural drawings for structure of the retaining walls. Drainage around the rating wall structure is also a very important aspect to be taken into consideration. The design of retaining walls must be able to resist pressures that are exerted on the earth. The retaining wall design needs to take parameters into consideration. These parameters include the height of the wall, the soil type, the land that is slopping above and below the retaining wall as well as the loads behind and above the retaining walls (Punmia and Jain, 2007). Soils parameters Some of the basic soil parameters that are necessary to be taken into consideration include the unit weight for the soil, the friction angle as well as cohesion. The lateral distribution of pressure is also an important parameter of consideration. The design of the retaining wall involves two phases which are; Clearly investigating the stability of the retaining wall in which case the sliding, bearing capacity and overturning failures are analysed in details. The second phase involves the checking of every part and components with regard to reinforcement and strength characteristics (Skinner, 2003). Soil parameters design calculation: Determination the maximum height of wall of isolated pier The formula that is taken into consideration in the calculation of this soil parameter is as follows; When the formula is reworked, the maximum height of the retaining wall is determined by; Where; tr = minimum thickness of the retaining wall = 230mm, H = maximum height for the retaining wall Cv = 33.5 Calculation of the earth pressure coefficient of the retaining wall; Lateral strain, εh = 0           ko  = lateral earth pressure coefficient at rest. Lateral earth pressure coefficient at rest, ko is dependent on type of soil, unloading and loading history and relative density of soil. For the soil type that is normally consolidate         For soil type that is over consolidated                               Where OCR refers to over consolidated ratio     For this particular design, the earth pressure coefficient, Ko Ko = 0.33/ (1-0.33) = 0.49 Section of the reinforced retaining wall Friction angle and cohesion The cohesion and friction angle used in the design of retaining wall are regarded as constants. These constants provide a description for soil properties. In the design considerations of the retaining wall, the friction angle and cohesion are critical in the estimation of stress levels and strength around the wall. Calculation of earth pressures in retaining wall design Piers which are cylindrically drilled indicate pressure loads that are active in between their spacing. Consequently, the calculation of active loads for the purposes of design is performed on the basis of tributary areas which have similarities in size with the central spacing for the piers. Retaining walls are designed to be able to cope with the distribution of hydrostatic active pressure. In situations of land slide, the zone of active loading us transferred to the sliding depths. This is because such walls usually experience an active deflection with confinement to the soil mass that is failing. In this situation, care is normally taken to ensure that the mass sliding does not become active in the process of construction. Otherwise the retaining wall is designed in such a manner that it carries the whole thrust of the sliding mass. In this particular design, the spacing between two consecutive centres of piers is meant to fall in the range of 2 to 3 times the diameter of the pier. The passive wedges that are subjected to dangers by pliers are positioned in an overlapping state which results in the negation of part of passive resistance in the view of a plan (Anderson, 2008). Determination of active and passive pressure forces using Euro code 7 These are pressures that come about when the expansion of soil mass is experienced. The active earth pressures stain in a downward direction as a result of free tilting of the retaining wall. The Rankine pressure envelops with an inclination of (45 – α/2) degrees considered from the smallest structure element. PA = ½ KaϒH2 Earth pressures and stability of slopes In reality, it is just the upper portion two thirds of a conventionally unrestrained stem has the capabilities of outward deflection. The one third portions at the bottom of the wall have sufficient stiffness to be able to deflect rigidity 0.002H to 0.02H. These particular areas are regarded as areas of rest pressures. Pressure diagrams of active earth pressure Method statement for construction phase of the retaining wall The method for the construction phase of the retaining wall involves five stages. The first stage involves carrying out surveys which are meant to provide guidance to the other stages that follow in the construction of the phase for the retaining wall. This exercise is carried out by a resident engineer after the submission of inspection request is made. The second stage in this method involves earthworks which are also known as excavation. Once the setting out process and the Acceptance by the resident engineer has been done, the earthworks commence. The earthwork activities involve the performance of excavation at the first sequence until the proposed level of platform is obtained. At this particular level, the performance of the sequence offers a large extent of diversion. The excavation works the proceeds to sequence two which offers accessibility to other activities at sequence one (Anderson, 2008). Stage three of the method involves the actual construction process of the retaining wall structure. This is carried out in four levels. The first level is that of the pilling works which is done beginning from the chain at the end of the retaining wall and continues to the front. The second level deals with the wall base construction. This begins immediately following the organization of reaches for pile head as well as actual practical length that is preferred for safe working area. All reinforcements that are installed are expected to be from the effects of rust and be appropriately installed in accordance with the specifications and drawings of the construction. The third level is concerned with concrete works which begins after the installation of the inspected and approved work sequence. The fourth level deals with construction of the retaining wall which follows after the completion of the concrete base (Punmia and Jain, 2007). Stage four is mainly concerned with backfilling to the retaining wall in completion. This begins as soon as entirely completed portion of the retaining wall is ready for receiving materials for back filling as well as having practical safety. Finally, the fifth stage is concerned with the performance of miscellaneous activities and it takes place upon the completion of the construction for entire retaining wall structure (Skinner, 2003). Risk assessment for construction phase of the retaining wall The assessment of risks for the retaining wall under design and construction involves all the parties and stakeholders that are taking part. The designers, the contractors as well as the masons are jointly in charge and share responsibilities when it comes to the identification, evaluation and assessment of risks that are associated with the retaining wall construction. The risk assessment exercise in this case generally involves identifying the points at the construction sites that may require in special considerations (Anderson, 2008). These special considerations may involve the reinforcement as well as design adjustments to avert the occurrence of accidents and the experiencing of cases of casualties. The activity extends to involve the assessment of the previously identified lapses in both design and construction of retaining walls. Other than that it also considers any features and characteristics of the retaining wall that may affect its bond type, control joints as well as its strength among other critical features. Boundary restraint Taking boundary restraint into consideration, the proposed structure of the retaining wall goes through risk assessment and evaluation considering issues such as the sequence used in the construction process. This includes the decision to use cross walls or the of those design types that offer support to each other. Structural foundations are also important considerations in this case. This happens with regard to careful examination of proposed or existing excavations as well as the walls or any other structures that are adjacent to the retaining wall under construction. The other important consideration is the establishment of the possible causes of adverse weather conditions towards the wall during and after its construction (Anderson, 2008). Reference Anderson, D. G. (2008). Seismic analysis and design of retaining walls, buried structures, slopes, and embankments. Washington, D.C., Transportation Research Board. Punmia, B. C & Jain, A. K. (2007). Limit state design of reinforced concrete. New Delhi, Laxmi Publications. Skinner, T. (2003). Segmental retaining walls: a building guide and design gallery. Atglen, PA, Schiffer Pub. Ltd. Read More