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首页> 外文期刊>Journal of Civil, Construction and Environmental Engineering >Geotechnical Considerations for the Design and Construction of Foundations in a Marshy Stream Channel of Iwochang - Ibeno, Eastern Niger Delta, Nigeria
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Geotechnical Considerations for the Design and Construction of Foundations in a Marshy Stream Channel of Iwochang - Ibeno, Eastern Niger Delta, Nigeria

机译：尼日利亚Iwochang湿流河道的基础设计和施工的岩土注意事项-尼日利亚尼日尔东部伊比诺

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A pre-construction site investigation was carried out in a marshy stream channel and adjoining areas for a proposed building site to characterize the subsurface subgrades and recommend foundation design for which proposed structures include a 1-floor 39.7m x 33.7m hostel, a 20.5m x 10.0m 4-bedroom duplex and a 1- floor 2-bedroom block of flats measuring 28.2m x 11.5m with 1.5 factored design dead + live load data as 2700tons, 655tons and 1270 tons respectively. Field investigations include boring of 10 boreholes to a depth of 10m using auger and sounding of 6 cone penetration tests using a 2.5tons mechanical cone penetrometer. The results indicate a soft clay layer existing from ground surface to a depth varying from 1.0m – 1.1m in the stream channel and 0.60m – 0.70m on the adjoining land. These clays are extra-sensitive to sensitive high compressibility Kaolin clays (CH – OH, MH - OH) with undrained shear strength varying from 42 – 75.0KN/m2, angle of internal friction ranging from 0 - 30 with cone resistance values of 3.0 – 11.0 Kg/cm2. Swell potential ranges from 11.45 – 30.64%, swell index from 0.44 – 0.57, activity from 7.0 – 11.0 and swelling pressure 4.776KPa – 4.890KPa. Below this depth a harder clay layer occurs to a depth of between 4.5m – 5.2m and is proposed to found the structures. Pre-consolidation pressures determined from Oedometer test on undisturbed clay samples retrieved from the centre of the second clay layer varies from 125.0KPa – 162.5KPa and Overconsolidation ratios from 2.75 – 6.40 depicting overconsolidation while water table corrected bearing capacities indicates a favourable fully compensated depth of 1.2m for the building foundations. However excessive total settlement determined using Boussinesq’s average vertical stress ranges from 180.1cm - 211.1cm on adjoining land and 160 -111.9cm on the stream channel under the worst case scenario for the structures necessitating further depth compensation to 2.0m. This yielded a reduction in settlement varying from 8.0% to 9.9% on the stream channel and 16.7% - 18.4% on the adjoining land. Rate of settlement depicts that it will take 6.655 and 28.65 years after construction to achieve 50% and 90% settlement under the worst case scenario. Below these clays are loose to medium density sands of varying grain sizes. Load transfer to these sands through pile foundations was considered using the cone penetrometer as a load test to derive unit toe bearing capacities of piles which embedment depth of 11.0m was recommended.
机译：在拟建的建筑工地的湿流河道和毗邻区域中进行了施工前现场调查，以表征地下路基并推荐基础设计，其中拟建结构包括1层39.7mx 33.7m宿舍，20.5mx 10.0宿舍m 4卧复式公寓和1楼2卧1居室公寓，面积为28.2mx 11.5m，带有1.5因子设计静载荷和活荷载数据，分别为2700吨，655吨和1270吨。现场调查包括使用螺旋钻在10m的深度钻探10个钻孔，并使用2.5吨的机械锥度仪进行6次锥孔渗透测试。结果表明，从地表存在的软粘土层在河道中的深度在1.0m – 1.1m之间，在相邻土地上的深度在0.60m – 0.70m之间。这些黏土对敏感的高压缩性高岭土（CH – OH，MH – OH）特别敏感，不排水的剪切强度范围为42 – 75.0KN / m2，内摩擦角范围为0 – 30，锥度值为3.0 – 11.0公斤/平方厘米。溶胀潜力为11.45 – 30.64％，溶胀指数为0.44 – 0.57，活度为7.0 – 11.0，溶胀压力为4.776KPa – 4.890KPa。在此深度以下，较硬的粘土层出现在4.5m-5.2m的深度之间，并被提议用于发现结构。由Oedometer测试确定的从第二层粘土中心取回的未扰动粘土样品的预固结压力在125.0KPa – 162.5KPa之间变化，而超固结比在2.75 – 6.40之间变化，这表明了超固结，而经水位校正的承载力表明，良好的完全补偿深度建筑基础1.2m。然而，在最坏的情况下，根据Boussinesq的平均垂直应力确定的过大总沉降范围在相邻土地上为180.1cm-211.1cm，在河道上为160 -111.9cm，需要进一步的深度补偿至2.0m。这导致河道上的沉降量减少，从8.0％降低到9.9％，相邻土地上的沉降量减少16.7％-18.4％。沉降率表明，在最坏的情况下，建造后需要6.655年和28.65年才能实现50％和90％的沉降。在这些粘土下面是松散的中粒度不同的砂子。考虑使用圆锥形渗透计作为载荷测试，通过桩基础将载荷传递到这些沙子，以推导建议的埋深为11.0m的桩的单位趾承载力。

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