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Iraq has the oldest railway network in the region. Currently the Iraqi railway company is rehabilitating the existing network in different regions and planning to expand it for the future. About 30–40% of the total length of the network is located in the southern part of Iraq, passing over soft, saturated, sedimentary deposits and in many areas close to the marshland. Stability and settlement are the major challenges to the safety and serviceability of rail tracks in these areas, thus ground improvement is essential to achieve the required level of performance. The paper presents results of tests of three treatment patterns. The first investigates the presence of a ballast embankment overlying a bed of soft, saturated clay. The second pattern focuses on the improvements achieved in load-carrying capacity and settlement as a result of eight stone columns added at an area replacement ratio of 0·196. The third pattern investigates the improvements achieved when patterns one and two are combined. In all tests, the ballast model embankment is loaded gradually by stress increments up to failure and stress deformation measurements are recorded and analysed in terms of bearing improvement ratio and settlement reduction ratio. Optimum outcomes are deducted from the third pattern, revealing bearing improvement ratio of 2·3 and settlement reduction ratio of 0·17.

This paper introduces an attempt to examine the effect of vertical monotonic load on the batter pile group models on its ultimate vertical load capacity. A fourteen steel solid pile models are used in this research. Three lengths of piles are selected (300, 400, and 500 mm) for embedment ratios (depth to width) 15 and 25, respectively. Batter piles are embedded in three different relative densities of sand bed (loose, medium and dense). The constant rate penetration test (CRPT) method was selected using a manufactured driving hammer to install the pile models in a steel box with dimensions (1000, 750 and 700) mm. The vertical cyclic load is conducted by a special hydraulic apparatus. The results indicate that the batter-vertical load capacity (BVLC) ratio increased by the increase in the embedded pile length. The batter pile group has a higher capacity at 20 degrees batter angle as compared with the vertical groups. Vertical pile groups exhibited more efficiency, which increases when pile length increases while decreases when the relative density is increased. The batter-vertical load capacity ratio increases when the embedded pile length increases and decreases with the increase in the relative density.

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