Allowable Bearing Research Articles

Empowering urban development: geospatial modeling and zonation mapping in New Kabul City, Afghanistan

The main difficulties in urban development, choosing a location, and creating preventative safety precautions are accurately characterizing and valuing subsurface soil information from a geotechnical and geological standpoint. This paper discusses how to define and build geotechnical subsoil soil zonation maps (SZMs) for the new Kabul city, Afghanistan, using traditional ArcGIS software assessing Kriging interpolation approaches. With the city’s expansion plans, including New Kabul City’s development, our research supports informed urban development strategies. Subsoil data from 2,13 locations across the city were collected from geotechnical studies, focusing on soil classification, Standard Penetration Test (SPT-N values), undrained shear strength, and consolidation characteristics up to 15 m depth. SPT-N and soil type were used to create SZMs, and other parameters were used to evaluate bearing capacity and settlement. The results revealed that SPT-N values divided the research region into three main sections: A (8–>50), B (13–>50), and C (14–>50). The subsurface strata consist of low-plasticity clay (CL) and clayey sand (SC) underlain by highly plastic clay (CH) and silt (MH). Linear regression predicted SPT-N values with depth, showing a strong R2 of 0.95. This speeds up sub-soil stiffness and strength assessments during building project planning and feasibility studies. The shallow Kabul foundation has an allowable bearing capacity of over 100 kPa, making it suitable for lightly loaded buildings. Predicting SPT-N levels has an 85% correlation coefficient, while soil type has 94%. Accurate geotechnical data on the soil’s underlying layers will help characterize the site and identify future project risks.

Response of a Coral Reef Sand Foundation Densified through the Dynamic Compaction Method

Dynamic compaction is a method of ground reinforcement that uses the huge impact energy of a free-falling hammer to compact the soil. This study presents a DC method for strengthening coral reef foundations in the reclamation area of remote sea islands. Pilot tests were performed to obtain the design parameters before official DC operation. The standard penetration test (SPT), shallow plate-load test (PLT), and deformation investigation were conducted in two improvement regions (A1 and A2) with varying tamping energies. During the deformation test, the depth of the tamping crater for the first two points’ tamping and the third full tamping was observed at two distinct sites. The allowable ground bearing capacity at two disparate field sites was at least 360 kPa. The reinforcement depths were 3.5 and 3.2 m in the A1 and A2 zones, respectively. The DC process was numerically analyzed by the two-dimensional particle flow code, PFC2D. It indicated that the reinforcement effect and effective reinforcement depth were consistent with the field data. The coral sand particles at the bottom of the crater were primarily broken down in the initial stage, and the particle-crushing zone gradually developed toward both sides of the crater. The force chain developed similarly at the three tamping energies (800, 1500, and 2000 kJ), and the impact stress wave propagated along the sand particles primarily in the vertical direction.

Conceptual design and experimental investigation of regolith bag structures for lunar in situ construction

Lunar habitat construction is a critical engineering requirement in lunar exploration missions, characterized by unique structural and material challenges distinct from Earth. To meet the demands of in situ large-scale construction in extreme lunar environments, a general mode of “Prefabricated core module & Inflatable structure &In situ materials structure” is adopted. This work analyzed the structural internal forces and foundation bearing capacity for lunar habitats, highlighting the significance of structural tensile performance and the foundation's allowable bearing capacity. A construction scheme based on regolith bags is proposed, encompassing architectural and structural design, and long-term planning. Multiscale experimental investigations conducted on “material, component, structure, and construction” levels confirm the excellent properties of regolith bag. Aramid fabric and CUG lunar regolith simulant were chosen for material and component testing, focusing on evaluating the regolith bag's performance under tension and compression. Successful construction demonstrations of a regolith bag arch structure and a regolith bag – airbag structural unit validate the feasibility of this construction scheme. Conclusively, the proposed lunar habitat construction scheme based on regolith bag technology provides a viable and efficient method for in situ lunar construction.

The Evaluation of Pipeline Protection Influenced by Causeway Embankment Using the Finite Element Method (FEM)

The construction of embankments over very soft to soft clay, such as reclamation projects, is on the rise. One such development is the reclamation project in the District Manyar, Gresik region of East Java. The seabed in this area is predominantly composed of soft clay. Reclamation involves the construction of a causeway that intersects with a gas pipeline at a depth of 5 m from the seabed. The embankment construction will undoubtedly impact the surrounding area. This study focuses on analyzing the impact of embankment in a reclamation area on soft soil on the underlying pipeline and designing pipeline protection. As a result of this study, the safety factor at each construction stage exceeds the planned safety factor of 1.5. The maximum settlement that occurs in the soil beneath the pipe is 26.91 mm. The maximum stress sustained by the corrugated steel plate (CSP) is 35,499.79 kN/m2, with a lateral deformation of 41.37 mm. The maximum stress occurring on the concrete footing slab is 123.40 kN/m2, which is smaller than the allowable bearing capacity of 128.61 kN/m2.

Development of geotechnical properties geo-database for soil in Kano metropolis to enhance building construction

Building collapse is a prevalent and concerning issue that resulted in significant loss of lives and properties in many places in Nigeria including Kano state and determination of Geotechnical properties of soil could play a crucial role in preventing building collapse. This study uses Geographic Information System (GIS) methodologies to create a geospatial database of soil properties in Kano Metropolis. The database, created using Inverse Distance Weighting (IDW) and spatial interpolation techniques, provides 212 sets of soil properties being meticulously mapped across the study area. These meticulously generated maps illustrate various soil characteristics prevalent in the metropolis, offering invaluable insights for preliminary designs and construction planning for buildings within Kano Metropolis. The soils in this area are predominantly classified as CL (Clay of low plasticity), SC (Sandy Clay), and SM (Silty Sand) using Unified Soil Classification System (USCS). The moisture content spans from 2.01 to 46%, specific gravity within the range of 2.32 to 2.75, liquid limits varying between 17.2 and 45%, plastic limits within the range of 10.1 to 40.5%, and linear shrinkage values spanning from 1 to 13%. Furthermore, the shear strength parameters of the soil across the study area varies. The unit weight varies between 15.61 and 22.16 kN/ m3 , the cohesion (c) values ranging from 1.28 to 29.1 kN/m2 , and the angle of internal friction (ϕ) spanning from 5.5° to 32.2°. Despite variations in ultimate and allowable bearing capacity with depth, the ultimate bearing capacity (qult) generally ranges between 108 and 1150 kN/m2 , with the corresponding allowable bearing capacity (qall) falling between 40 and 343 kN/m2 . This research provides valuable geospatial knowledge to engineers, architects, and construction professionals in Kano Metropolis, enhancing decision-making and project planning precision, ultimately contributing to sustainable development and growth of Kano metropolis.

Geotechnical investigation of soil bearing capacity a case study of Nile university of Nigeria

Geotechnical investigation was conducted within Nile University soil with the aid of the master plan showing areas awaiting future developments. This is as a result of the university planning for infrastructural expansion due to such in student’s population. Each time a building construction is to be taken place, the university management spent another set of money on conducting geotechnical investigation. There are no comprehensive geotechnical information of the soil bearing capacity that can represent the whole of Nile university space/area of 1,153,208,008?2. In-situ and laboratory test were carried out. Three boring point were established using map at a regular interval and drilled to a depth where basement was encountered. In each test sample were collected at 1.5m interval. The standard penetration procedure consist of split spoon and u-tube as set forth in ASTM-1990. The test involves counting the number of blows required to drive a spoon sampler by 300mm, using a weight of 64kg hammer with a free fall of 76mm on the anvil of a rod arrangement. An initial penetration of 150mm is allowable on the sampler known as sitting blows before counting the subsequent blow for the required 300mm. another six trial pit were evenly spread at regular interval at different location within the university. It was manually excavated by hand, undisturbed and disturbed sample were extracted by hand auger and shovel. Sample were extracted at 1.5m depth, properly labelled and taken to laboratory. The laboratory test of the extracted soil sample include moisture content, grain size distribution, liquid limit, plastic limit, consolidated drained test and unified soil classification system was adopted. It was observed that the results obtained from Standard Penetration test indicates variance in allowable bearing capacity with depth, between 0.0-0.5m is 56??⁄?2, 0.6- 1.0m is 112??⁄?2, 1.5- 2.0m is 215??⁄?2, 3.0 – 3.5 is 279??⁄?2, 4.5 – 5.0m is 273??⁄?2. The soil type were predominantly medium dense to very dense inorganic silty sand with clay content less than 5%. Point of refusal was encounter at 6m depth, boring was then terminated. The Direct shear box test analyses obtained from site BC and CH gave the allowable bearing capacity values of 250??⁄?2 at pit one, 211.2??⁄?2 at pit two, 798.1??⁄?2 at pit three, at pit four, 798.1??⁄?2, at pit five, 918??⁄?2 , at pit six 960.5??⁄?2, but with the results obtained from oedometer test show that we cannot adopt this allowable bearing capacity value due to it high settlement rate beyond the acceptable settlement rate set by Development Control in Nigeria, which is 100mm. therefore based on the result from oedometer test the allowable bearing capacity of 120??⁄?2 was adopted with a safe consolidated settlement of 52mm at site BC. While an allowable bearing capacity of 100??⁄?2 with safe consolidated settlement of 55mm was adopted for site CH. Site BC is predominantly underlain by Sandy Silt. While site CH the predominant soil type was Clayey Sand. Pad footing at 1.5m depth and 210??⁄?2 allowable bearing capacity should be adopted. It is recommended that for both site BC and CH pad foundation at 1.5m having maximum individual column load less than 600??⁄?2 with a ground beam adopted.

Expansive Soil Stabilization Using Steel Factory Dust

One of the geotechnical-engineering roles is soil stabilization, because it affects the long-term strength and functionality of structures. For suitability and durability of expansive soils for construction projects, shear strength, bearing capacity and other characteristics can be enhanced through the stabilization process. This study is focused on the effects of steel factory dust (SFD) as an additive on the improvement of the undesired geotechnical properties of expansive soil (CH soil). A series of laboratory tests were conducted on intact and treated samples. SFD was added by 0, 2, 4, 6, 8 and 10% to the dry soil. The conducted tests are consistency, specific-gravity, modified Proctor compaction, swelling-pressure and -percent and unconfined compression tests. The addition of SFD reduced the values of liquid and plastic limits, plasticity index, modulus of elasticity and allowable bearing capacity. Significantly, the 10% SFD addition significantly reduced swelling percent and pressure by 26.8% and 25.4%, respectively while notably increasing the unconfined compressive strength (UCS) from 475 MPa to 629 MPa. SFD was found to be a successful waste material in improving expansive soil by using 10% as the best addition percent, which usefully saves the environment. KEYWORDS: Expansive soil, Stabilization, Steel factory dust, Swelling, Unconfined compressive strength. INTRODUCTIO

Application of Geoinformatics in Civil Engineering Design and Construction: A Case Study of Ile Oluji, SW Nigeria

Subsoil engineering site condition and modeling of engineering parameters has been carried out in Ile Oluji, Ondo State, Southwestern Nigeria, using geotechnical investigation, geophysical method, borehole logging, groundwater level measurement, and laboratory studies. Findings revealed that the soils are clayey of low-high plasticity/compressibility, with AASHTO classification of A-7-6. Based on average values of cohesion (48.4 KN/m2), angle of friction (17.4°), unconfined compressive strength (186.8 KN/m2), coefficient of permeability (2.13E-06 cm/s), activity (0.48), soaked CBR (7 %), MDD/OMC (1980 kg/m3/14.8 %), plasticity index (20.2 %), group index (6 %), compression index (0.0443), coefficient of volume compressibility (0.2041 m2/KN), depth to basement rock (22.2 m), static water levels 5.5 m (in well) and 21.8 m (in borehole), the soil is unsuitable for highway subgrade, subbase, and base courses. Thus, if it is expedient to use it as subgrade soil, the minimum recommended thickness is 241 – 513 mm (avg. 395 mm). The average allowable bearing capacity of the soil for square and round foundations are 268.4 KN/m2 and 267.95 KN/m2 respectively, with average total settlement of 18.3 mm for structural pressure of 100 KN/m2. For embankment, the suitability index (1.21) of the soil suggests a fair/expanding not collapsible construction material. The rock units in the area have high compressive/shear strength, modulus of elasticity, high crushing strength, low deformability; and presumable bearing capacity of 8, 000 – 10, 000 KPa when fresh, and 5000 – 7000 KPa when partly or slightly weathered. Thus are valuable as foundation constructions, aggregate in pavement, building stone, and armourstones. The correlation coefficient of the parameters are: MDD/PI vs. CBR (0.0043), LL vs. coefficient of consolidation (0.0608), PI vs. undrained shear strength/effective overburden (0.2706), PI vs. angle of shearing (0.0117), dry density vs. angle of shearing (0.0058), suitability index vs. CBRs (0.3644), clay contents vs. PI (0.1355).

ANALISIS KAPASITAS DAYA DUKUNG PONDASI DANGKAL TERHADAP KEDALAMAN (STUDI KASUS: KALIMANTAN)

The bearing capacity of the foundation is the ability of the soil to withstand the pressure or load of the building on the ground safely without causing shear failure or excessive decrease. The bearing capacity value of a soil is based on the characteristics of the subgrade soil. The analysis was conducted using the Mayerhoft (1963) and Hana (1981) methodologies in the West Kalimantan and South Kalimantan areas. The results of calculations at the South Kalimantan location yielded values of 11.9 kN for the load P = 5 kN with a depth of 0.5 m and dimensions of 1x1 m, and 11.9 kN for the load P = 10 kN with dimensions of 1x1 m at a depth of 0.5 m. The West Kalimantan location obtained values for loads P = 5kN and 10kN with a depth of 0.5 m, so this condition is unqualified for the allowable bearing capacity. Compared to areas in West Kalimantan, South Kalimantan is still able to satisfy the requirements for shallow foundation bearing capability.

Integration of GIS with the Generalized Reciprocal Method (GRM) for Determining Foundation Bearing Capacity: A Case Study in Opolo, Yenagoa Bayelsa State, Nigeria

This study addresses the pressing need to assess foundation bearing capacity in Opolo, Yenagoa, Bayelsa State, Nigeria. The significance lies in the dearth of comprehensive geotechnical data for construction planning in the region. Past research is limited and this study contributes valuable insights by integrating Geographic Information System (GIS) with the Generalized Reciprocal Method (GRM). To collect data, near-surface seismic refraction surveys were conducted along three designated lines, utilizing ABEM Terraloc Mark 6 equipment, Easy Refract, and ArcGIS 10.4.1 software. This methodology allowed for the determination of key geotechnical parameters essential for soil characterization at potential foundation sites. The results revealed three distinct geoseismic layers. The uppermost layer, within a depth of 0.89 to 1.50 meters, exhibited inadequate compressional and shear wave velocities and low values for oedometric modulus, shear modulus, N-value, ultimate bearing capacity, and allowable bearing capacity. This indicates the presence of unsuitable, soft, and weak alluvial deposits for substantial structural loads. In contrast, the second layer (1.52 to 3.84 m depth) displayed favorable geotechnical parameters, making it suitable for various construction loads. The third layer (15.00 to 26.05 m depth) exhibited varying characteristics. The GIS analysis highlighted the unsuitability of the uppermost layer for construction, while the second and third layers were found to be fairly competent and suitable for shallow footing and foundation design. In summary, this study highlights the importance of geotechnical surveys in Opolo’s construction planning. It offers vital information for informed choices, addresses issues in the initial layer, and suggests secure, sustainable construction options.

ANALISIS STABILITAS BLOK ANGKUR/BACKSTAY JEMBATAN GANTUNG JURANGSARI KABUPATEN SEMARANG

The suspension bridge construction program is part of President Joko Widodo's Nawa Cita Program, namely developing Indonesia from the outskirts. The location of this research is the Jurangsari Suspension Bridge Construction Project, Semarang Regency, while the object of this research is the stability of the anchor blocks.In this research, calculations were carried out on the stability of the anchor blocks. The data used includes design drawing data and soil investigation data at the location. The data was processed and analyzed using the Excel spreadsheet program.The results of the analysis concluded that the stability of the anchor block at the service limit conditions was safe against shear with SF=5.5 > 1.5 and overturning SF= 57.0 >1.5 while under extreme conditions/seismic it was safe against shear with SF= 6.81 >1.1 and overturning SF = 21.09 >1.1. The bearing capacity of the soil to withstand its own weight and the forces acting on the anchor block in the conditions of safe service limits on the allowable bearing capacity with maximum s= 132.52 kN/m2 and s minimum = 119.26 kN/m2, s maximum <s permit 292.137 kN/m2 or 2.20 times greater than the s maximum that occurs, whereas in extreme conditions the soil tension that occurs at s maximum = 190.09 kN/m2 and s minimum = 142.74 kN/m2, s maximum <s permit 292.137 kN/ m2 or 1.54 greater than the maximum s that occurs. Settlement that occurs in the anchor block under safe service limit conditions is Si = 0.441 cm and in extreme conditions is Si = 0.633 cm, both conditions the safety factor for the decrease is £ 1.0 cm.

Using GIS for the allowable soil bearing capacity estimation according to the Terzaghi (1943) equation in Eskişehir city center, Türkiye

In foundation engineering, it is necessary to calculate the bearing capacity of soils. The allowable soil bearing capacity required for foundation design is calculated through various empirical methods using geotechnical parameters such as specific gravity and angle of internal friction. Standard Penetration Test (SPT) values of the soil are used in these calculations. Therefore, soil tests which engineers need, are costly and time-consuming. This study aims to determine the soil bearing capacity of Eskişehir city according to the Terzaghi (1943) equation and present soil bearing capacity maps for shallow foundations. The geotechnical parameters of the soil were obtained from 40 borehole data made in the field. Within the scope of the study, according to the Terzaghi (1943) equation bearing capacity maps were created for 0-5 m depth to provide an overview of the bearing capacity of Eskişehir soil. These maps were made in the Geographic Information System (GIS), which has a database that stores and analyses regular data. In addition, these maps can assist engineers working on shallow foundation design on the site.

Field tests on partially geotextile encased stone column-supported embankment over silty clay

Various researchers have highlighted that geosynthetic-encased stone columns could be used in place of stone columns (SCs) in very soft soil. In this study, field load tests are performed on individual partially geotextile-encased stone columns (pESCs), individual stone columns (SCs), and a field embankment reinforced with pESCs and SCs in silty clay. Although the material cost of pESCs is designed to be comparable to that of SCs, the tests reveal that pESCs display a higher allowable bearing capacity and stress concentration ratio and less residual settlement than SCs. The embankment reinforced by pESCs is found to incur fewer lateral displacements, while there is no improvement in the drainage performance during the construction period compared to the SCs. For the pESCs, 51–66% of the pressure acting on the top of the column propagates to a depth of z = 1.2 m, wheras, for the SCs, it is only 21–55%. Furthermore, to estimate group behaviour, the ultimate bearing capacity of an individual pile composite ground can be extrapolated. However, individual pESCs achieve much higher stress concentration ratios than the pESC group.

Evaluasi Daya Dukung Pondasi Tiang Pancang Pada Gedung Universitas Muhammadiyah Lamongan

The pile foundation is a deep foundation that is often used in the construction of high-rise buildings and small-scale buildings. The foundation is required to have a greater bearing capacity than the load on it. This study aims to determine the maximum bearing capacity of the foundation against the work load including the additional load from the 15-story Lamongan Muhammadiyah University building which was found to be cracked. Calculation of the bearing capacity of a single pile is carried out to determine the bearing capacity of a single pile using the Mayerhoff, Reese O'neil, and Reese and Wright method. Calculation of the bearing capacity of group piles is carried out to determine the bearing capacity of piles in one group using the Converse-Labarre, Los Angle Group, and Seiler-Keeney methods. Controlling the bearing capacity of single and group pile foundations, whether they are able to withstand the load on them using the axial loads and moments obtained. The results of the calculation of the bearing capacity of a single pile foundation at a depth of 30 m using the Meyerhoff calculation method obtained the carrying capacity of a single pile permit (Q_a) at point DB-1 of 916,80 tons and DB-2 of 916,80 tons, Reese and O' neil obtained Power single pile permit bearing (Q_a) at point DB-1 of 668,67 tons and DB-2 of 668,67 tons, Reese and Wright obtained single pile permit bearing capacity (Q_a) at point DB-1 of 1.070,08 tons and a DB-2 of 1.070,08 tons, while the shamanic strength of the largest pile group foundation was obtained using the Converse-Labarre method with ultimate bearing capacity using the Reese anad Wright method, bearing configuration from the pile group capacity (Q_g) (2 x 2) obtained at point DB -1 of 9.733,45 tons and DB-2 of 9.733,45 tons, configuration (2 x 3) at point DB-1 of 13.810,45 tons and DB-2 of 13.810,45 tons, configuration (3 x 2 ) at point DB-1 of 13.810,45 tons and DB-2 of 13.810,45 tons. The results of controlling the bearing capacity of the foundation by looking at the value of the allowable bearing capacity is greater than the value of the axial load (P ≤ Q_g). From the calculation of the bearing capacity of the piles it can be concluded that the pile foundations at points DB-1 and DB-2 are safe.

Behavior of foundation piles resisting lateral forces in soft soil

The role of the foundation in construction is crucial. Foundation planning aims to ensure that it can support loads up to a specified safety limit, including the maximum load that may be encountered. The foundation serves as the lower structure that interacts with the soil, providing stability and support for the superstructure. In this study, the analysis focused on the bearing capacity of the pile foundation under lateral forces. The Brinch Hansen method was employed to determine the allowable lateral bearing capacity, while the computer application was used to calculate the lateral deflection. Various pile lengths, such as 20m, 25m, 30m, 34m, and 40m, as well as different dimensions, including circular piles with diameters D30, D35, D40, and square piles measuring 30x30, 35x35, and 40x40, were considered. The analysis revealed that square cross sections exhibited greater allowable lateral bearing capacity compared to circular cross sections. The square sections showed smaller lateral deflection values in comparison to the circular sections.

Research on the Relationship between Soil Shear Stress Level and Safety Factor

At present, in the design of geotechnical structures, the allowable bearing capacity is mostly designed according to the safety factor specified in the design specification. However, there are two problems that have not yet been clearly explained in theory: (1) why is the safety factor listed in the standard is suitable for the design of geotechnical structures and (2) can the safety factor selected according to the specification guarantee the long-term stability of soil mass. In view of the above problems, according to the statistical law in the rheological properties of soil, the relationship between the shear stress level of the soil and the stability of the soil is studied, and the stable shear stress level of the soil is obtained. The research results show that the stable shear stress level of soil is the corresponding shear stress level under static earth pressure. This conclusion not only verifies the correctness of the theoretical finding that “the earth pressure on the structure develops toward the static earth pressure, and whether the ultimate safety of the geotechnical structure is related to its design bearing capacity is greater than the static earth pressure” in the design code of the retaining structure but also clarifies the source of the safety factor. By calculating the design bearing capacity of the geotechnical structure according to the static earth pressure, the geotechnical structure that maintains long-term stability can be designed, which provides a reliable method for the design of the permanent geotechnical structure.

Evaluasi Penggunaan Fondasi Bore Pile Pada Bangunan Gedung Pelayanan Madrasah Aliyah Negeri Insan Cendekia Bengkulu Tengah

Based on data from the Bengkulu Province Bappeda, there were 3,341 buildings collapsed due to the failure of the lower structure (foundation). In the Service Building of Madrasah Aliyah Negeri Insan Cendekia, the foundation used can be considered inefficient. The reason is that the number of foundations is the same at each point even though each point has a different load and floor height. This study aims to evaluate the bearing capacity and the need for bore pile foundations in the Service Building of Madrasah Aliyah Negeri Insan Cendekia using quantitative methods. Based on the calculation of the ultimate bearing capacity (Qu) and allowable bearing capacity (Qizin) of the foundation, obtained (Qu) 208,992 tons, (Qizin) 65, 234 tons (Mayerhoof Method) and (Qu) 208,992 tons, (Qizin) 62,775 tons (Method Guy Sanglerat). The evaluation of the need for foundation piles using the Mayerhof method is the largest at the point of foundation one (P1) 3 foundation piles and the smallest is at the point of foundation five (P5) 1 pile foundation. Based on Guy Sanglerat's method, the largest foundation needs are at foundation points one and two (P1 and P2) 3 foundation piles, the smallest at foundation point five (P5) 1 foundation pile.

Comprehensive Characterization of Soils with Analytical and Numerical Simulation for Bearing Capacity and Settlement Requirements of the Footing

Characterization and analysis of foundation material are basic concerns of geotechnical activities to have safety for the structure and users as well. Particularly, it is quite important for the areas of lagging experiences with a lack of equipment and accessibility to investigate the subsurface conditions sufficiently. This study was designed for comprehensive soil investigations through analytical and Plaxis 2D simulation by considering square footing in Bule Hora town, Southern Ethiopia. Considering the investigation depth up to 5.0 m, fourteen soil samples at 1.5 m and 3.0 m depths (two samples from seven pits) were collected, and physical and engineering properties were investigated. Grain and consistency results indicated that soils lying between low to high plastic silt regions. Undrained shear strength (Cu) ranges from 49.5-–64.30 and 52.40–103.10 kN/m2 at 1.5 m and 3.0 m depth, respectively. An average allowable bearing capacity of 145.35 kN/m2 with a settlement of 40.77 mm at 1.5 m depth and 191.41 kN/m2 with a settlement of 47.84 mm at a depth of 3.0 m using the analytical method whereas 122.72 kN/m2 was obtained with the settlement of 30.57 mm at a depth of 1.5 m and 155.11 kN/m2 with 29.08 mm at depth of 3.0 m using Plaxis 2D analysis. The results of bearing capacity and settlement analyzed by the numerical method are lower than the analytical method, which confirms that comparatively, Plaxis 2D analysis gives a better output in selected square footing of shallow foundations. In conclusion, Plaxis was a preferable analysis tool for a shallow foundation, square footing, using inputs of the exhaustively investigated actual condition of soils specifically in Bule Hora town.

Geotechnical Considerations for Foundation Design in Parts of Yenagoa, Bayelsa State, Niger Delta Nigeria

This research was to determine geotechnical properties of the subsoils in some part of Yenagoa and environs to obtain proper foundation design parameters, six towns in Yenagoa local government area, Bayelsa state was investigated. Six geotechnical boreholes was drilled and laboratory studies of soils samples were obtained from 0-20.25m deep. Subsurface soil profiles were delineated followed by determination of their index and mechanical properties, including Atterberg limits, particle sizes distribution, undrained shear strength, shear box test and consolidation coefficient. The general soil profile consists of (from top to bottom), , upper Silty clay horizon (0.0-5.25m thickness) soft to firm for Yenagoa study areas, Medium silty clay horizon (0.75 to 1.5m thickness) soft to firm Yenagoa study areas, low clayey sand horizon (0.75 to 1.5m thickness) soft Yenagoa study areas, peaty clay (1.0m thickness between 3.0-4.0m) soft Igbogene Yenagoa, upper sand horizon (3.0m thickness) silty sand Etegwe town Yenagoa, lower sand horizon (13.5 to 18.0m) silty sand to fine to medium and medium coarse appear in all the boreholes in Yenagoa. Yenagoa sub-soil show clay of high plasticity, silt of intermediate to high plasticity (CH, MI and MH) according to unified soil classification system from the results it shows that pad foundation is more economical in the study areas. Raft foundation is more economical in the six towns study areas of Yenagoa with Allowable bearing capacity of the upper clay layer ranges from 23-128KN/m2 In view of the significant variations in the stratification and engineering geological index properties of the soil in the six towns in Yenagoa while geotechnical data of one location cannot be used as a basis for design of foundation in a nearby land. Axial load carrying capacity for 305, 306mm, 356, 360mm, 406mm, 600and 610mm diameter for bore pile and tubular driven steel cased piles respectively were calculated for all the studies areas. Where high rise building is required in the various study areas. The study shows that the frequent causes of building collapse in Yenagoa are as a result of inadequate geotechnical investigations of the subsoil, poor quality materials, and poor work supervision.

Engineering Geological Properties of Subsurface Soils for Foundation Purposes in Parts of Bayelsa State, Niger Delta

The geotechnical properties of soil samples obtained from eight (8) boreholes from some parts of Bayelsa State were determined to assess their suitability as foundation materials. The geotechnical characteristics of the soils were determined from the laboratory and field works. The Atterberg limit results reveal that the liquid limit ranges from 46.5% to 98.3%, the plastic limit ranges from 23.5% to 56.3% while the plasticity Index values range from 17.1% to 51.3%. The clays are highly plastic (CH) in the USCS designation. The natural moisture content ranges from 35.9% to 91.3%, the moisture content is relatively high, this could be attributed to the wet season period of sampling. The particle size analysis disclosed that the cohesionless samples are predominantly fine to medium and medium dense sands. The triaxial test results shows that values of Cohesion (C) ranges between 16 – 40KN/m2 and the friction angle (ϕ) ranges between 3 – 6o. The result of the undrained shear strength of the clay ranges between 20Kpa and 24Kpa. The coefficient of consolidation (Cv) of the clay soil samples varies between 1.13 m2/yr and 2.89 m2/yr, the coefficient of volume compressibility, (Mv) for these same materials varies between 0.215 m2/MN and 6.338 m2/MN. Generally, indicating clay layers of high to very high compressibility. The calculated values for ultimate bearing capacity (qu) and allowable bearing capacity (qa) varies between 100.29KN/m2 to 151.49 KN/m2 and 33.42 KN/m2 to 50.50 KN/m2 respectively. The analyses showed that the values of ultimate bearing capacity increases with depth. The calculated settlement ranges between 69mm to 653mm with the thickness of clay of 7.5m and 30.0m respectively. Raft foundation is best suited for these weak, soft foundation materials for light structural loads but for heavy structural load, a pile foundation is recommended.