Effect of adding fine gravel and cement on settlement of sabkha soil

تعتبر تربة السبخة هي احد أنواع الترب الانهيارية و تسبب الكثير من المشاكل للمنشآت المشيدة عليها إذ تمتاز بأنها قوية و متماسكة و هبوطها واطئ عندما تكون جافة و لكن بمجرد وصول الماء إليها فإنها تصبح ضعيفة جدا و تسبب هبوط عالي جدا. هذه الدراسة ركزت على استخدام معالجتين لهذه التربة، الأولى هي إضافة الحصى الناعم بنسب (6%, 4.5%, 2%) و أثبتت المعالجة لهذه الطريقة عدم حصول تحسين ملحوظ لهبوط التربة .اما الطريقة الأخرى فهي إضافة اسمنت بنسب (1.5%, 3%, 4.5%) مع حصى ناعم بنسب (4.5%, 6%) و قد حصل تحسن كبير في هبوط التربة حيث قلت بنسبة تتراوح بين (62% - 90%). Sabkha soil is one of the many types of collapsible soils and in turn is on of the many types of problematic soils. This soil is totally having good engineering properties when dry, i. e, moderately bearing capacity with low settlement .But once are wetted they loose their entire structure (collapse) and undergo very large instantaneous settlement .A laboratory model test consists of a cylindrical steel container of 270mm diameter and 300mm height, the soil is brought from Al-Khalis discrete .The density of soil is controlled by placing the required weight inside the container of known volume, to the required height .A square footing 60 x 60mm makes from steel is used .The stress is applied from a fixed loading system designed especially for model tests .In this study two types of treatment carried out ,the first treatment is added fine gravel only with percentages (2 %,4.5 %, 6 %) to soil which is not give good improvement .The second type of improvement is added 3 % of cement with fine gravel (4.5 %,6 %) percentages which give good improvement, reduced the collapsibility to 84 % .Also, when adding 3 % of cement with 4.5 % fine gravel to soil , give good improvement, reduced the collapsibility to 90 % .