Lltraviolet intensity and time exposure in controlling sulfate reducing bacteria in oil and gas pipeline

Abstract

When an embankment is to be built on ground that is too weak and compressible to support the embankment appropriately, columns of firm material can be installed in the soft ground to offer essential support by carrying the embankment load to a stiff stratum. This procedure is referred to as column supported embankments. There are two main motives to employ columns supported embankments: a) expedite construction compared to traditional construction techniques such as staged construction or pre-designed vertical drains, b) protection of nearby amenities against distress, like settlement of existing carriageways when a highway is being extended. Despite its extensive usage in the construction industry, the current situation of technology suggests that further investigation is needed to give a deeper understanding of the technology in reference to sustainable material used in column, performance and failure mechanisms of the columns underneath the embankment. In this study, the performance of a group of bottom ash, cement bottom ash and geopolymer columns in enhancing the load-carrying capacity of soft soil under embankment were investigated. A series of laboratory physical model test was carried out to examine the behaviour of improved ground under an embankment subjected to constant strain loading. The influence of key parameters such as column materials, length of columns and area replacement ratio on the performance of improved ground was investigated by the overall number of 13 model tests. The research variables include two column lengths of 150 mm (floating) and 200 mm (end bearing), three area replacement ratios of 11%, 16% and 22%, three column materials such as bottom ash (stone column), cement bottom ash and geopolymer (rigid column). In addition, numerical analysis was carried out in parallel to model the behaviour of laboratory model tests by using Plaxis 3D foundation software. It is evident from the results that the load-carrying capacity of the foundation soil under embankment increased significantly with columns installation. The load-carrying capacity of bottom ash columns reinforced clay with the area replacement ratio of 11%, 16% and 22% increased by 24.31%, 39.09% and 63.35% for the floating columns and 27.49%, 42.63% and 83.60% for the end bearing columns as compared to the unreinforced model. Cement bottom ash columns reinforced clay with an area replacement ratio of 16% and 22% increased the load-carrying capacity by 19.53% and 69.39% for the floating case and 53.00% and 78.24% for the end bearing columns in comparison to unreinforced test. While geopolymer columns reinforced ground with an area replacement ratio of 16% increased the load-carrying capacity by 64.47% and 83.48% for the floating and end bearing columns, respectively. The results showed that the area replacement ratio and column length significantly affect the performance of reinforced ground. The load-carrying capacity and stiffness of foundation soil under embankment enhanced by increasing the area replacement ratio and column length. In addition, bottom ash columns reinforced ground showed perfectly plastic behaviour failure, while cement and geopolymer columns reinforced ground under embankment possess ductile behaviour failure. Bulging as a mode of failure occurred in the bottom ash columns, while tilting and punching occurred in the cement bottom ash and geopolymer columns. The stress concentration ratio was greater than unity for column reinforced models. Furthermore, the experimental and numerical results showed good agreement. The stress-settlement curves achieved from both experimental and numerical models followed the same pattern. Preliminary design charts were produced from the relationship between load-carrying capacity and area replacement ratios for different length to diameter ratios of bottom ash, cement bottom ash and geopolymer columns. The design charts will help the construction industry in designing bottom ash, cement bottom ash and geopolymer columns.