The secant pile of the wall consists of two parts: primary and secondary piles. Primary piles should be drilled first and built using ‘soft’ cement-bentonite mix or ‘firm’ weak concrete. Such materials help create a temporary water seal system and give some time for constructing a future system for waterproofing and drainage system. After that, it is necessary to build the secondary piles using structural reinforced concrete, which will give sufficient strength. This construction method is known as the ‘hard/soft’ or ‘hard/firm’ system. Compared with the ‘hard/hard’ system, it is more economical because it does not use structural-grade concrete for both piles.
The fills are usually loose and heterogeneous materials. It has a low friction angle and apparent cohesion. Consequently, it often shifts laterally, which can cause problems after the construction is done. Non-contiguous retaining wall systems, such as a soldier pile wall, cannot hold the fill. It happens because it can get into the excavation spot through the gap. On the contrary, contiguous systems such as secant pile walls or sheet pile walls can stop the fill overflow.
A high water tablet is the water table identified at about 4 meters above the bottom of the excavation site. It imposes significant water pressure on the retaining wall system. Moreover, the area may also be flooded since fill, alluvium and sandy clay are porous. Thus, the construction requires a solid and water-resistant system. The secant pile wall provides this opportunity and increased alignment flexibility in construction, increased wall stiffness compared to sheet piles, and low levels of noise during construction.
The most productive method of lateral support is adding the anchoring and propping system. Propping can be installed from base to wall at an inclined angle. The second potential lateral support is an anchor. When anchoring the wall deep into the soil behind, the pressure created by soil can be transferred to the anchor as shear stress. Nevertheless, the anchoring system is not the most broadly used system for the proposed site because it is prone to damage and may disturb the neighbor foundations. Moreover, the loose-fill material cannot provide sufficient shear capacity.
A capping beam is a tool to distribute significant vertical column loads to the piles. It can also be used as a part of a temporary propping system. For instance, it might help during the basement excavation. Active pressure in soil mechanics means that the soil deforms with lateral extension. On the contrary, passive pressure means that the ground deforms with lateral compression. The increase in depth of the retaining wall makes the left side active pressure neutralize some of the right active pressure and lower the rotation point. It is a natural method to ensure that the wall will not fall into the excavation site.