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What is with this photo?

posted Sep 9, 2018, 8:13 AM by jeffery jim

I'm intrigued with this photo. Do you think this is an engineering marvel? It renders the masculine part of engineering but does this demonstrates ludachris feat in construction? Exposing slender structural members to such duress?

No one should even consider doing such thing. The secant wall surrounding the structure spells danger when the equilibrium have been shifted by giving additional moment (with the increase of arm distance from the fulcrum) to react. This allows rotation and subsequently slip or overturn. Slip and rotation linked to the loosening of soil and hydrostatic pressure reacting on both the secant wall and borepiles of the structures.

The outcome of such event gradually change the state of the soil from being passive to be active. The over excavation allows water to penetrate and causes swelling of clay in a short run where additional skin friction will be sufficient to withstand the vertical load. Like most CH or CI soils, the moment water starts to dissipate, the swelling will reduce and subsequently reduces the friction between soil and structure. For non-cohesive soil, liquefaction will do more damages than one can imagine.

Such reduction means loss of skin friction and less resistance available to carry such load/stress apart from loosing significant amount of area on the borepile for skin friction due to excavation. This leads to settlement. Due to strata change, load(s) are disseminated or propagated unevenly (skin friction value varies), and the settlement will be uneven. Hence, this will leave the structural members to be deflected or worst deformed. Although deformation usually leads to serviceability limit state, it will further deteriorate structural members and certain aggravation leads to ultimate limit state such cracks and the ingress of chloride ions which leads to pitting.

Therefore, i believe this kind of temporary work is uncalled for and dangerous.