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In the study presented herein, a simple method for laboratory calcite cementation of a reconstituted gravelly sand was presented. This method was used to prepare cemented gravelly sand specimens, which have similar natural characteristics to alluvial deposit of the city of Tehran. The formation and distribution of calcite bonds, as well as the effectiveness of the presented calcite cementation method in increasing interparticle cohesion, as observed in weakly to moderately cemented soil in Tehran, were evaluated by means of chemical analysis, X-ray diffraction technique, and unconfined compressive strength tests. The cementation technique was used to prepare triaxial specimens with calcite contents ranging from 1.5 to 6 %. Then, a series of monotonic and cyclic undrained triaxial tests was performed to characterize the behavior of calcite-cemented gravelly sand with different calcite contents under different loading conditions. In comparison with the specimens with zero calcite content, the cemented specimens exhibited a distinctly different behavior in terms of static stiffness and strength, cyclic pore pressure generation, and cyclic strength. Results of the monotonic triaxial tests indicated an increased shear strength with an increase in calcite content and confining pressure in the tested soil. Because of the presence of interparticle cohesion, cemented soils behaved less compressive during cyclic loading, and accordingly, the rate of positive pore pressure generation in these specimens was lower during loading with smaller induced plastic deformations.

Background: There is no consensus regarding the clinical benefit of interbody fusion cage in the treatment of Spondylolisthesis (SL). This study aimed to evaluate the effect of posterolateral fusion combined with interbody fusion cage on the spinopelvic parameters and the pain level of the patients. Objectives: Role of interbody fusion in the treatment of spondylolisthesis Methods: This prospective study included 40 SL patients who underwent surgery following the failure of conservative management. The Meyerding classification was used to grade SL. Also, the visual analog scale was used to measure the level of pain, before and after the operation. Spinopelvic parameters included total kyphosis, sagittal vertebral axis, pelvic tilt, pelvic incidence, and lumbar lordosis. Results: The Mean±SD age of the patients was of 53.4±11.6 years. In four patients (10%), SL occurred at two levels. Besides, the etiology was degenerative in 21 cases (52.5%) and isthmic in 19 cases (47.5%). The grade I, II, and III of SL were detected respectively in 17, 17, and 6 cases (42.5%, 42.5%, and 15%, respectively). The Mean±SD preoperative value of the sagittal vertebral axis was 43.1±33.1 mm, which improved to 24.8±22.3 mm after the surgery (P<0.001). Also, the Mean±SD preoperative value of the pelvic tilt significantly improved from 19.2±10º to 17±9.1º (P=0.049). Moreover, the Mean±SD score of the visual analog scale improved from 9.1±0.8 to 2.8±1.2 (P<0.001). The clinical and spinopelvic parameters greatly improved in patients with degenerative SLs, single-level SLs, and the lower grades of SL. Conclusion: Posterolateral fusion combined with interbody fusion cage improves both the clinical and spinopelvic parameters of SL patients and could be suggested as the treatment of choice for these patients.

The paper deals with an experimental study of the undrained cyclic behavior of a natural coarse sand and gravel deposit located in Tehran, a megacity situated on the continental side of the Alborz Mountain in Iran. Membrane compliance that plays a significant role in inhibiting redistribution of pore pressure and liquefaction in undrained cyclic triaxial tests performed on coarse granular soils is studied in this paper. Currently there is no or little satisfactory method for accounting for this phenomenon for gravelly soils, and thus the non-compliant cyclic loading resistance of granular soils and the evaluation of the behavior of such material in natural and in situ state are not easily determined. A procedure has been proposed in this paper for consideration of membrane compliance effects on the pore pressure measurements during cyclic loading. A method is also introduced to verify the proposed procedure by employing lightly cemented specimens. In addition, some new correlations for excess pore water pressure ratio against the number of cycles to failure have been presented for a non-compliant system under various effective confining and deviatoric cyclic stresses applied on reconstituted and isotropically consolidated specimens. Initial liquefaction has been observed during the tests with or without consideration of membrane compliance; however, the number of cycles to initial liquefaction is higher for the compliant case.

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