CAPÍTULO 5. CONCLUSIONES Y REFLEXIONES FINALES
III. ESTRUCTURA DEL TRABAJO
2.4. COMPETENCIAS EMOCIONALES: CONCEPTO Y CLASES
2.4.2. Delimitación del constructo competencias emocionales…
The proposed projects lie within the Quaternary deposits of marine clays. The site is within the old river which has been reclaimed. The boreholes carried out at Project A show that the interbedded layers silty sand in the marine clay as depicted in Figure 21.
During the investigation, 26 number of boreholes were drilled outside of the two proposed projects with the objectives of mapping the subsoil profile, water profile and soil properties within the proposed project sites. Piezometers were installed in most of the boreholes to monitor the water profile almost perpendicular to the edge of the excavation. Settlement profiles along the lines were also measured. In addition, some 306 houses were monitored for the activities of the cracks using tell-tale glass and crack gauge.
The results of the original ground investigation indicate the present of sand layers within the marine clay especially near the toe of the sheetpiles, where a layer of sand of about 7m thick present. The surface water profile during the investigation as indicated by Figure 22 indicates the groundwater on the retending side has dropped significantly especially near the excavation indicating seepage through the sheetpile wall. The seapage continued and resulted in the profile shown in Figure 20. Every drop of a metre of groundwater would increase the effective overburden pressure by 10kPa which is equivalent to about half a metre of compacted earthfill. As the drop of water level reduces with distance away from the excavation, the increase in effective overburden also reduces respectively. The increase in effective overburden pressure induces immediate settlement to cohesionless soil and consolidation settlement to cohesive soil. It was the differential settlement or distortion that caused the formation of new cracks and widened with time.
The remedial proposal for Project A was carried by installing an additional row of sheetpiles of about 30m penetrating into the relatively impermeable clayey soil underlying the sandy soils together with recharging well and these had effectively restored the water table to its original level.
Resumption of further basement excavation was only granted after the monitoring confirmed the effectiveness of the remedial measures. Similar trend of the drop in water level was observed at Project B where the water level near the excavation has dropped by 5.3 m.
The remedial proposal included the casting of its basement for the excavated portion to prevent further seepage and recharging wells were also introduced to expedite the recovery of the water level. The investigation also found that more reports of cracks were received from shophouses on or near the old Prangin River or its tributaries and swamps which had been reclaimed more than 100 years ago as shown in Figure 23.
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5.0 CONCLUSION
The success of the design and construction of a deep excavation begins from well planned and closely supervised subsurface investigation works including field and laboratory testing. The design of retaining wall and support system should follow the appropriate standards, guidelines, and good practices. Intimate input from design engineer at every stage of the construction starting from setting out and establishing monitoring instruments before any excavation is essential. The construction should also follows the approved method statement and have a checklist on supervision to prevent mistakes or carelessness in the execution of works especially those highlighted in this paper.
Quality assurance system should be implemented to ensure design and construction are carried out systematically with the necessary checklists. Due care and diligence with full conscience from the design and supervision teams are imperative to ensure success of engineering works in particular for deep excavation which is risky not only to the work but also to adjacent structures.
ACKNOWLEDGEMENT
The authors acknowledge and thank the staff of SSP Geotechnics Sdn Bhd, particularly Ms.
Barbara Ng for the many series of word processing and preparation of figures and tables from the drafts to the final paper.
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