Journal of the Structural Engineering and Geotechnics
Volume:12 Issue: 2, Summer and Autumn 2022

For a long time, our country has faced natural disasters. In recent years, it has imposed various levels of damages on the country, including those caused by wars (military maneuvers) and natural disasters (earthquakes such as Rudbar Manjil, Bam, and Azgeleh), and floods in cities and regions). Every year, severe floods, hurricanes, explosions, and terrorist attacks cause great suffering for millions worldwide. In a disaster, whether natural or humanitarian, it is vital to provide immediate help to those affected, but relief can often be severely interrupted, significantly if the infrastructure is damaged and the transport network is disrupted. Here, the bridge will be constructed from nonidentical prefabricated elements based on modularity. Construction of modules and final assembly is done off-site (in a factory). Because it can be deployed on-site, it transported the completed bridge in a compact form. SAP2000 software evaluated an emergency bridge's seismic design and performance using nonlinear static and dynamic analysis to save lives in the shortest amount of time, cost, construction, and installation, while also considering the structure's performance. Also, its portability is the goal of this structure. In this system, space structures were used to design the project, absorbing much energy outside their elastic range and was innovative. As a result, the ultimate bearing capacity of the space trusses will depend on the structure's geometry, the position of the supports, and the displacement load response of each member.

If the saturated sand lenses are placed around the tunnels under the force of the earthquake, liquefaction will occur in them. This will cause settlement of the ground surface and changes in forces and anchors on the tunnel lining. For this purpose, it is important to evaluate the change of different parameters of the sand lens and the change of the thickness of the tunnel lining in the part of the sand lens and the changes in the diameter and depth of the tunnel as well as the location of the sand lens considering the tunnel inside it. Therefore, this article investigates the mentioned changes in shallow tunnels in the location of sand lens in flowing soils surrounded by clay. In this article, FLAC 3D software is used to determine changes in pore water pressure and effective stress reduction after sand lens liquefaction. Based on the obtained results, if the sand lenses are placed at a depth of less than 10 meters, they increase the land surface subsidence by 36% compared to the reference model B, with an increase of 2 meters in the depth of the sand lens compared to the reference model B, the value of the maximum bending anchor and axial force on the tunnel lining increases by 35.7% and 14.4%, respectively, in the sand lens part. The findings of the present study can be very useful in the decision-making process of tunnels that are dug inside flowing sand lenses.

In projects that involve surcharge and prefabricated vertical drains (PVDs) systems for the treatment of weak underlying layers, embankment failures, tension cracks, and differential settlements, surficial heaves, and foundation failures were addressed in various literature. Overestimation and unrealistic design assumptions made by geotechnical and structural engineers are the main reasons for most of the cases. In all these cases a simple collaboration between different parties in the project ranging from designers to field engineers could have decreased or prevented these undesirable outcomes. The problem of neglecting the infiltration of the embankment in the ground as a new distinct layer with all the necessary requirements, and also disturbance caused as a result of PVDs installation in four cases: preloading case, fill removal, main structure construction, and post- construction phase are discussed. A few design recommendations are given regarding the stated issues. Since after the completion of soil treatment operations, the soil engineering parameters and in some cases even soil stratification had changed, care should be taken to use the new treated parameters in the final design process, not the preliminary site report parameters. Neglecting this issue may lead to severe malfunctions and even unpredictable failures. BIM technology has the possibility of integrating all aspects, and complexities of geotechnical engineering in the structural-architectural platform as a whole, which would revolutionize the construction industry. Till now only the structural-architectural part is done and further research and investment are necessary for the geotechnical aspect.

In this research, the performance of tunnels with segmental lining in swelling rocks have been studied. In this regard, the way segments are arranged in relation to each other, how the segments are connected along the longitudinal and circumferential lines of the tunnel, and the extent of creating the excavation wall, the effect of the thickness of the segment and the lining system, the effect of the depth of the tunnel and other details are studied. In this regard from the FLAC 3D software was used for numerical modeling. Among the important results obtained in this research, the displacements of the tunnel after applying the boundary conditions and modeling the segments and taking into account all the elements and the phenomenon of creep and surrounding stones with accurate values as the average initial displacement around the tunnel at the specified points are 4.63 mm, this displacement continues the upward trend with a steep slope for a week and increases up to 6.49 mm, and after a week, the increasing rhythm decreases and reaches 6.92 on average in 50 days, and this trend increases again. After 400 days, it reached the value of 9.85 and then the increasing rhythm decreased again, so that after 11 years, the average displacement reaches the value of 11.09, and after this period of time, the displacement of the tunnel becomes very insignificant.

The finite element procedures are extremely useful in gaining insights into the behavior of reinforced soil retaining walls. In this study, a validated finite element procedure was used with Abaqus for conducting a series of parametric studies on the performance of gabion facing wall with 2m vertical spacing Geo-grid under different surcharge loadings. The performance of the wall was presented with facing horizontal deformation along wall height, and compare to centrifuge model and field measurements. The soil properties include density, Young modulus, Poisson’s ratio, and internal friction angle were among major variables of investigation. At low loading conditions, the impact of increasing density has a significantly greater effect on the deformation of the wall compared to high loads. As the loading increases, the effect of reducing the Young’s modulus on deformations decreases. Moreover, with increasing loading, the effect of deformations due to the decrease in internal friction angle increases, but the rate of this increase decreases. The influence of Poisson’s ratio on the deformation of the walls has decreased with increasing of loading. The results show that by the increase in load, even at a shallow depth, the applied stresses on the soil increase, leading to greater deformation of the soil above the wall, and the maximum magnitude is created at a higher elevation.

A multi-hazard investigation approach is a vital requirement for a realistic risk assessment of infrastructures. The combined impact of scouring and earthquake can result in a distinctive effect on the performance of a given bridge. Scouring, being a hazard influenced by various factors, entails numerous uncertainties. Several prior investigations have explored the multi-hazard of scour-earthquake; however, the associated implementation has not accounted for the random scour depths around the foundations of differing bents. This study provides a probabilistic platform to investigate the effect of random scouring on the seismic performance of a multi-span RC bridge. In this regard, researchers employed Monte Carlo simulation to develop a probability hazard curve for scour. The Latin Hypercube technique was applied to randomly select depths, enabling the generation of non-uniform patterns for the depth of cavities formed in different foundations. Subsequently, the study involved conducting non-linear time history analyses on the finite element model. The uniform scouring patterns were also examined to compare the models. The scouring around foundations significantly affects the responses of bridge elements, as it influences the total base shear of the structure and the pounding forces between the superstructure elements.