15This study aims to investigate the ability of using biopolymer (environmental friendly material) to enhance 16 the mechanical characterizations of collapsible soil. Two types of biopolymers were used in this study 17 (xanthan gum and guar gum) because of their stable behaviour under sever conditions and their availability 18 with reasonable prices. The experimental program focused on three major soil properties, which are; 19 compaction characterizations, collapsible potential and shear parameters, these three properties are 20 essential in any soil improvement process. Different biopolymer concentrations were used in this study and 21 the experimental program was performed at two curing periods (soon after mixing the soil with the 22 biopolymer and after one week curing time). shear parameters were measured for the treated specimens in 23 both soaked and unsoaked conditions, while a collapsible potential test was performed under different 24 mixing conditions (wet mix and dry mix). A numerical model was built to predict the behaviour of the 25 treated collapsible soil after and before inundation. The analysis of results indicated the ability of both 26 xanthan gum and guar gum to be used as soil improvement materials for collapsible soil treatment. The
27collapsible potential has been reduced significantly from 9% to 1% after mixing the soil with 2% 28 biopolymer concentration in the wet case. After one week curing period, the cohesion stress has been 29 increased from 8.5 to 105 kPa by increasing the xanthan gum concentration from zero to 2%, leading to 30 overall improvement in the soil shear strength. Also, it proved that the superiority of guar gum over 31 xanthan gum in improving the shear strength is about 30% more than xanthan gum at the same conditions 32 and reduces the collapsible potential by about 20% more than xanthan gum at the same conditions. 33 34 35
Pneumatic flow mixing method is a new land reclamation method, developed in Japan to meet the persistent lack of space. In this method dredged soft soil is mixed with a small amount of stabilizing material (such as cement) during transporting the soft soil in a pipe using compressed air to be used for land reclamation. In some cases, the soil/cement mixture is stored in temporary place for days and then transported and compacted at the required place. Basically, the cement chemical reaction starts immediately after the mixing with the soft soil and the mixture starts to gain its strength, therefore disturbing the mixture after days from the mixing influences the mixture strength. However, the soil/cement mixture is still able to gain extra strength after disturbance, transportation, and compaction. This study aims to evaluate the effect of dynamic compaction on the shear strength of disturbed cemented soft soil mixture experimentally. The mixture was fully disturbed after one week from mixing with cement. Three cement/soil ratios were used in this study under different dynamic compaction energies. Unconfined compression test was conducted at various curing times for both disturbed and non-disturbed specimens. Keywords Pneumatic flow mixing Á Stabilized soft clay Á Compaction Á Unconfined compressive strength Á Soil disturbance List of Symbols aw Cement ratio E 50 Modulus of deformation t Curing time q un Unconfined compressive strength q un_Non Unconfined compressive strength for nondisturbed cemented clay q un_Non_t Unconfined compressive strength for nondisturbed cemented clay at curing time t q un_D Unconfined compressive strength for disturbed cemented clay q un_D_T Unconfined compressive strength for disturbed cemented clay without compaction q un_D_T_t Unconfined compressive strength for disturbed cemented clay without compaction at curing time t q un_D_comp Unconfined compressive strength for compacted disturbed cemented clay q un_D_comp_t Unconfined compressive strength for compacted disturbed cemented clay at curing time i Increasing factor (i = q un_D_comp_t / q un_D_T_28) G s Average specific gravity for the specimen c w Water unit weight c t Total unit weight after curing c d Dry unit weight after curing e Void ratio after curing time R 2 Coefficient of determination
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