Exfiltration from sewers: effects of different types of leakage / Mohd Ashaari Ab Wahab ... [et al.]

This research was conducted to study exfiltration of wastewater from gravity sewers. Exfiltration through different types of sewer leaks were studied. With the different size of leakage areas and a constant thickness of soil bedding, it was found that the exfiltration rate reduces and became constant over a duration of one (1) to three (3) days. Knowing the exfiltration rate, the time taken for the polluted water exfiltrate from sewer pipes to reach the groundwater can be determined so that preventive measures can be taken to prevent it. From studies conducted, it can be shown that the size of the leakage area was found to play an important role in determining the size of the clogging zone, the increased in the clogging zone resulted in the decreased of exfiltration rate due to the accumulation of organic matters at the edge of the leakage area and trapped in the pores of the bedding soil

Performance comparison between polyurethane foam and cement grouting slab replacement for soft ground improvement at shallow depth using finite element model

Two methods of ground improvement have been proposed to overcome excessive and differential settlement problem of soft ground foundation for infrastructure such as road, highway and parking space namely polyurethane (PU) foam and cement grouting slab. It has been executed by excavating and replacing the soft soil at shallow depth with the proposed ground improvement methods. The ground improvement methods able to minimise the excessive and differential settlement as the shallow depth of soft soil is removed and replaced by the stiff materials, thus the load can be distributed evenly to the underlying soil. The comparison of performance between both methods are evaluated in this study by carried out finite element analysis for soft ground problem namely PLAXIS. The results show that the settlement can be reduced significantly to the tolerable amount by applying PU foam instead of cement grouting slab as the increase in thickness of cement grouting slab cause the increase in settlement. On the other hand, the increase in PU foam thickness has not contributed to further settlement as the PU foam is lightweight, however, the soil may experience upward displacement due to insufficient overburden load to counter uplift