IMPROVING SEISMIC RESISTANCE OF HYDRAULIC STRUCTURES USING SOIL IMPROVEMENT TECHNIQUES
Most of the Egyptian irrigation structures were built many decades ago. Most of these structures may be classified as unsafe structures when making an assessment of their resistance to earthquake loads in accordance with the current specifications. This research suggests a technique to increase the ability of these structures to resist seismic loads. The suggested technique depends on using soil improvement methods to improve the most stressed soil bulb zone under the structure. The effect of seismic site soil factor will be decreased by improving this part of soil. Controlled soil jet grouting technique could be used for the existing structures. Other types of soil improvement techniques such as soil mixing could be used for new structures or other types of earth structures. Numerical study was performed to investigate the feasibility of the suggested method. Experimental study was carried out to validate the numerical study. The dynamic responses of an improved location and normal location were measured. The two locations were subjected to the same excitation force. The measured responses were compared and evaluated. Based on the results of the suggested technique, a real site condition for an existing barrage structure was numerically analyzed before and after soil improvement to examine the suggested technique.
NUMERICAL SIMULATION OF SHAKING TABLE TESTS ON DYNAMIC RESPONSE OF DRY SAND
In this paper, experimental results obtained from dynamic tests with laminar shear box with dimensions of 1 by 1 by 1m, on Babolsar dry sand models are compared with numerical simulation results. Response of two types of dense and loose level ground models excited with harmonic loadings was observed. Different physical parameters like displacement of layers, accelerations at internal points and surface settlements were measured during tests. For numerical analyses, first the analyses were done with one-dimensional softwares like EERA (Equivalentlinear Earthquake site Response Analysis) and NERA (Nonlinear Earthquake site Response Analysis). These codes are based on equivalent linear methodology. Then, more precise modeling of the laminar shear container and its inside sand is conducted using famous finite element software ABAQUS. Due to very small frictional coefficient between box layers, in numerical modeling of laminar shear box this effect was neglected and proper boundary conditions were used for model. Also, in order to obtain more real results in 2D level ground analysis and avoiding reflect of waves from side boundaries into the model, infinite elements and quiet boundaries were used. The numerical analyses were performed for model scale. In all cases the computational results were compared with real and measured values for different physical parameters.
Ground improvement by means of jet-grouting
After a description of jet-grouting technology some typical examples are given of its applications to a number of civil engineering problems. The following aspects are examined: suitability for dif...