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Abstract The present study evaluates the geotechnical and mechanical properties of expansive shale of Dakhla and Esna Formations. The samples are collected from El-Balas area, west of the Nile, Qena, and from El-Quraya area, east of the Nile, Qena, Egypt. Using Hydrometer test it is found that Dakhla Formation from the two localities has about 73% silt, while Esna samples from El Ballas area (EB) have 83% silt, and Esna samples from El- Quraya area (EQ) has about 91% silt. All studied samples contain about 2% fine sand and the other particles are clay size. The studied shale samples have high plasticity index ranging between 15 to 27. The shale samples tested, are classified according to unified soil classification system USCS as MH (inorganic clayey silt with high plasticity index). However, according to highway research board classification system H.R.B/(AASHTO), they are classified as A-7-5 (fair to poor sub-grade).from the results it can be concluded that; the tested samples are expansive shale (> 90% free swelling) due to their high content of clay minerals and need to be stabilized to reduce the swelling. Three different additives are used in the stabilization program of the studied samples as lime (L), cement kiln dust (CKD), and mixture of L/CKD. Based on pH-test it was founded that; the optimum contents of additives used for stabilization of Dakhla Formation were as follow; 4% in case of using lime, 10% in case of using CKD, and 2% lime with 8% CKD in case of using a mixture of them. In case of Esna Formation; the optimum contents of additives are 4% in case of lime, 10% CKD, and 2% lime with 8% CKD in case of using a mixture of them.Proctor test according to (AASHTO, T99) is used to detect the optimum water content (OWC) for natural and treated samples. Unconfined compressive strength values (qu) revealed that using CKD alone can increase the strength of the treated samples more that using lime, however a mixture of lime and CKD can also increase the strength but using CKD without lime is more cost effective. Also the strength increased with increasing curing time 7 to 28 days. The strength of stabilized DB samples increased to its maximum (1450.09 Kpa) when treated with 8% CKD and cured for 28 days. In case of DQ qu-values increased to its maximum (1301.89 Kpa) when stabilized with 3% lime plus 8% CKD mixture 28 days curing time, also it reaches a high strength value (1290.56 Kpa) when stabilized with 12% CKD and cured for 28 days. However; qu-value of EB samples reaches its maximum (1927.05 Kpa) when stabilized with 2% lime plus 6% CKD and cured for 90 days. Also its strength increased to (1847.47 Kpa) when stabilized with 10% CKD and cured for 90 days. While EQ samples reaches its maximum strength (1696.97 Kpa) when stabilized with 10% CKD and cured for 90 days.Free swelling percent of the studied shale samples decreased significantly when the samples treated with lime, CKD, and lime/CKD mixtures. The free swelling of DB samples decreased from 80% to 2.67, 3.33, and 0% when treated with 3% lime, 8% CKD, and 2% lime plus 6% CKD, respectively, at 90 days curing time. Free swelling of DQ samples are reduced to minimum value when treated with 10% CKD and cured for 90 days (from 104 to 4%). Free swelling percent of EB samples are decreased from 98.33 to 7% when treated with 2% lime plus 6% CKD and curd for 90 days. However, the free swelling of EQ samples were reduced when treated with lime, CKD, and lime/CKD, where free swelling percent of all samples are reduced to ≤ 10%. Some of the studied treated samples has high swelling percent, that proved the formation of ettringite mineral which considered as expansive mineral. Ettringite is resulted from the hydration of calcium sulfate, which present in the shale, lime, and CKD.Ultrasonic P-wave velocity test proved its effectiveness in measuring the geotechnical properties of the studied samples. The results are very resembles to the unconfined compressive strength values. Increasing Vpvalues with increasing curing time proved the reducing of pore size of the treated samples. In case of DB sample the Vp reached its higher values (1373 m/sec) when treated with 8% CKD and cured for 28 days. In case of DQ samples Vp increased to its maximum value (1629 m/sec) when stabilized with 12% CKD and cured for 28 days. However, Vp of EB samples reached its maximum value (1730 m/sec) when stabilized with 10% CKD and cured for 90 days. While EQ reached its maximum Vp-velocities (1598 m/sec) when stabilized with 2% lime with 6% CKD mixture and cured for 28 days, also it reached up high velocities (1519 m/sec) when stabilized with 10% CKD and cured for 90 days |