Nehemiah® Wall is a type of reinforced soil system based on Anchored Earth concept whereby the mode of stress transfer from the back-fill to the reinforcement is by passive resistance in addition to friction. This System is reinforced by galvanised steel bars and anchored by precast concrete blocks. The facing is vertical consisting of modular hexagonal shaped concrete panels interlocked together.
The schematic representation of Nehemiah® wall is as shown below:
Schematic representation of Nehemiah Wall systems
The facing panels are hexagonal shaped and are made of precast concrete (grade 30). They interlock with dowels bars with tolerance for horizontal movements. The horizontal joints between the panels are inserted with compressible material to allow for vertical movement. As such the facing is flexible and can tolerate large differential settlement.
The reinforcing bars are made of carbon steel rods in compliance with BS 8006-1:2016 Code of practice for Strengthened/reinforced soils and other fills. The bars are hot-dipped galvanized to prevent corrosion. The advantage of using round bars instead of strips is that they are more durable against corrosion in view of the reduced surface area exposed. The bars are connected to the facing panels.
The anchor blocks are discrete precast concrete blocks which act as deadmen. A hole is pre-formed in the center of the block to enable the reinforcing bar to pass through. The bar is then connected to the block with bolts and nuts. The advantage of using anchor blocks is that they enhance the pull-out resistance of the reinforcing bars. As a result, the use of cohesive frictional material as back-fill is possible since the system does not rely so much on friction for the stress transfer.
Generally speaking, the backfill consists of granular material. The advantage of granular material is that it is self-draining. This self-draining characteristic helps to reduce hydrostatic pressure. Hence, the overall stability of the wall is enhanced. The granular material also provides better frictional properties which help to improve internal stability of the wall. However, in a situation where the granular material is not available, cohesive frictional fill can be considered for use as backfill. However, the fill has to be tested and subject to fulfillment of certain technical properties.
Nehemiah® Wall is more cost effective than conventional types of earth retaining structures. Cost savings can be as much as 30%, depending on the height of the wall and the subsoil condition.
Rapid and Easy Installation
The construction of Nehemiah® wall is rapid and easy because the process is highly mechanized. Only a few skilled and unskilled laborers are needed. The time taken for construction of Nehemiah® Wall is much shorter because the casting of panels can be done simultaneously while site preparation and foundation work are on-going. The erection of the wall can also go on alongside back-filling, thus further minimizing construction time.
The precast facing is aesthetically pleasing in appearance. Various architectural finishes, including logos of companies, can be designed and imprinted onto the facing panels to further enhance the wall appearance. Colored facing panels have been used to achieve attractive and unique finishes.
Nehemiah® Wall is flexible and may withstand substantial total and differential settlement. In view of its flexibility, the need of piled foundation on marginal ground can sometimes be dispensed with thereby achieving further cost savings.
The design of Nehemiah® Wall is carried out in full compliance to BS 8006-1:2016 "Strengthened/ reinforced soils and other fills". The design life span can stretch up to 120 years.
The Nehemiah wall is applicable in a wide range of situations.
Nehemiah® wall can be used to repair failed slopes. The wall acts as a gravity buttress at the toe of the slope to provide stability to the slope. Due to the critical and urgent nature of slope failure problem, the speed of erection of Nehemiah® wall is an added advantage.
The requirements for railway application are similar to highway application except that the settlement criteria for railway embankments are more stringent. The relatively flexible nature of the Nehemiah® wall enables the wall to withstand the dynamic forces due to vibration from the trains.
Bridge abutments using Nehemiah® walls are an integral part of flyovers, highways and road over rail bridges. In this application, the Nehemiah® abutments are either load bearing or otherwise depending on subsoil conditions.
Of all the various applications, applications on urban highways and interchanges is the most popular. This is because the Nehemiah® wall is ideal for fill situation which is the case for most of the highway interchanges. Construction is rapid and the interference with the vehicular traffic is minimum because the wall can be erected from behind.
URBAN HIGHWAY INTERCHANGES AND FLYOVERS
Nehemiah® walls are also used as river walls for flood mitigation purposes and river bank protection. In this case, the river channels are widened and deepened. By doing so, the discharge capacity of the river channels is increased thereby bringing about flood mitigation.
When a highway goes through a hilly terrain, the challenge here is to design a highway that is not too winding and yet cost effective. The Nehemiah® embankment walls offers a solution that is not only cost-effective but also enables the highway to span across deep valleys. As a result, the highway is less winding and travel distance is reduced. In order to reduce cut and fill which minimizes environmental impact, the Nehemiah® wall can be designed using trapezoidal cross sections whereby the reinforcing elements are shorter at the lower levels.
Nehemiah® walls are regularly used for housing development to gain usable flat land especially in urban areas where the land cost is high.
Similar to housing development, industrial estates use Nehemiah® walls to gain usable flat land for their development.
Plain, ribbed and JKR logo finish.
Granit and embossed.
Granit and plain.
Bush, hammer and plain.