Reducing Settlement of Soft Soils Using Local Materials


The present work investigates the settlement behaviour of weak soils which cover the middle and southern part of Iraq. Physical and chemical properties were studied for weak soil brought up from Baladroz city, Dyalah Governorate. To decrease the excessive settlement of soft soil under study, reed materials which are widespread at Iraq marshes and geogrid materials were selected as reinforcement materials. For this purpose, steel container with dimensions (500 ×250 ×20 mm)and square footing (80 × 80 mm) were used.To prepare the soil with sameproperties of soft soils, the quantity of water was calculated using the liquidity index formula with LI equal to (0.42) corresponding to undrained shear strength of (10 kPa). This value of liquidity index was chosen according to the previous studies which showed that the liquidity index of such soil is ranging between (0.2 – 0.5).The results of soil model under the applied stress (5, 10, 15, 20, and 25 kPa) marked that the maximum settlement reduction (S/B) is get when the reed mat or geogrid mat is used directly under the footing and this value decreases with increase of the distance between the surface layer and position of the reinforcement. Also, the settlement improvement (St/Sunt) can be clearly seemed for all cases of improvement compared with settlement of untreated soil It is worth noting, that to achieve the durability of the reed in the soil, asphalt coating must be used to prevent the reed decay.