Abstract: Incessant incidences of building collapse in Lagos have continued unabated in recent times. Although, several probable causes have been highlighted .Unfortunately, the subsurface earth conditions have rarely been given any serious consideration prior to construction exercise. Geophysical and geotechnical laboratory test on soil samples were done on the subsoil within the study area. Cone penetrometer test and a standard penetration test were also conducted to identify the depth to competent layer as a compliment for VES survey. The VES identified three distinct geo-electric layers; the top soil, peaty clayey sand, medium grained clayey sand and very stiff clayey sand. The resistivity and thickness of each layer were in the range of 145-351.34 Ωm and 3.1-4.3m; 49.1-97.2 Ωm and 10.7- 11.4m, 41.4-105.6Ωm respectively. The CPT and SPT tests show that the subsurface around the area consist of materials of very low shear strength (< 80 kgf/cm2) interpreted as peat/clay at near surface to a depth of 11.50 m (being the maximum depth probed by the CPT test) and 11.4 m for the SPT. The Plastic, Liquid Limit, Plasticity Index, Natural moisture Content, Maximum Dry Density, Optimum Moisture Content and Unconfined Compressive Strength ranges are 20-40%, 40-70%,20-30%,1.71-2.04g/cm3, 3.76-6.224% and 75– 90KN/m2 respectively. The existence of loose sand, peat and clay near at the surface is capable of endangering building structures. The result so far proved that the buildings in this area is on a shallow foundation which is considered inappropriate, hence the differential settlement of the structure.

Abstract: The main objective of this paper is to identify the factors that have the potential to negatively affect the relation between the main contractors and their subcontractors in Saudi Arabia and to determine their level of severity from contractors' viewpoint. A total of 41 factors were identified in this study, with identification of factors influencing relation between the main contractors and their subcontractors being based on a careful review of literature and suggestions from local experts in construction industry. Contractors have ranked the following factors as top 10 factors with high potential to negatively affect the relation between the main contractors and their subcontractors: contractor delay in contract progress payments, non- adherence of the subcontractor to the time schedule, incomplete understanding of the main contractor to the contract documents, delay of the owner in releasing payments to the main contractor, frequent change orders by the owner, shortage of equipment or machinery at the sub-contractor, low experience and low capability of the main contractor, awarding the work to the subcontractor with lowest price, low experience of the consultant's team, and contractor delay in shop drawings and sample material approval.