This paper presents the results of the reliability-based design of pad foundation based on the results of the geotechnical investigation of the soil sample collected at 1m to 5m depth in Abuloma Community, Rivers State. Three boreholes, namely BH1, BH2 and BH3 were excavated utilizing a manual auger to depths of 1m, 2m, 3m, 4m, and 5m respectively. Laboratory investigations were conducted on the soil samples in the laboratory to determine the geotechnical properties of the soil such as soil cohesion, Poisson’s ratio, unit weight, angle of internal friction, and modulus of elasticity of the soil respectively. The bearing capacity of the soil at each selected location was obtained using Terzaghi’s bearing capacity formula. The results of the laboratory investigations on the soil properties such as cohesion, Poisson’s ratio, specific weight, internal friction angle, and elasticity modulus of the soil were used to conduct the reliability assessment and reliability-based design of the pad foundation at Abuloma using the method of response surface. The descriptive statistics of the geotechnical parameters were obtained utilizing a statistical tool called Minitab 17.0. The Full Factorial method of design of Experimental Design was used to obtain the design points. The types of probability distribution of the basic random variables were established using Anderson Darling Statistics. The performance functions were developed were developed considering bearing capacity and immediate settlement failure of the pad foundation at the four selected locations. The First Order Reliability technique implemented in MATLAB was used in the reliability estimates. The findings revealed that the Abuloma soil is safe only for a foundation pressure of 50KPa and for foundation pressures of 50KPa, 100KPa and 150KPa respectively when considering settlement criterion. The reliability indices generally decreased with increase in values of variation coefficient of soil cohesion, internal friction angle and soil density respectively. The MATLAB code developed is very easy for application geotechnical and coastal applications.

The high environmental impact and cost of cement-based construction materials have intensified the search for sustainable alternatives. This study investigates the mechanical, durability, and microstructural performance of compressed stabilized earth blocks (CSEBs) incorporating Parkia biglobosa (Makuba) as a bio-based stabilizer. Lateritic soil was characterized using particle size distribution, Atterberg limits, and compaction tests, while Makuba extract was chemically analyzed. Blocks were produced with varying Makuba contents and cured for 7–28 days. Compressive strength, water absorption, and microstructural properties (SEM, EDX, XRD) were evaluated. Results show strength improvements of 25–60%, with peak values exceeding 3.0 N/mm², satisfying Nigerian Industrial Standard requirements. Water absorption decreased by 15–35%, remaining below 12%, while microstructural analysis revealed pore refinement, enhanced particle bonding, and matrix densification. The findings confirm Makuba as a viable low-cost, eco-friendly stabilizer capable of producing durable structural earth blocks suitable for sustainable housing applications.