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.
STRENGTHENING AND REHABILITATION TECHNIQUES FOR MASONRY HYDRULIC STRUCTURES-A CASE STUDY ( PART 1-ASSESSMENT )
Barrages are considered one of the most important water structures in Egypt. It is very important to keep them working in good condition to assure water management in good manner. Most of these barrages have been built many decades ago using burned clay bricks and still in service till now. The construction cost of new barrages is very expensive, so, maintaining, repairing and strengthening these structures are an economical option that cannot be ignored. Many reasons cause defects in masonry hydraulic structures. These defects affect the structure capacity and performance. The causes of defects should be understood to be treated in optimum way. Structure assessment is the basic step to restore the structural capacity and to assign the suitable repairing technique. The aim of this paper is to present guidelines for the assessment of the masonry barrages when repairing, strengthening or upgrading is required. This could be achieved through reviewing the international experience in that field beside the gained experience from the many barrages upgrading projects. The paper displays a case study for assessment process for a typical masonry barrage type in Egypt. This study provides a solid basis for integrating all the monitored/output data into practical assessment of barrage system performance.The results of this study can also help to develop the current design codes.
Development of an in situ method to measure nonlinear soil behavior
One of the key variables in evaluating the response of geotechnical materials during strong earthquake shaking is their nonlinear behavior. This behavior is often expressed in terms of the nonlinear reduction in shear and constrained moduli with increasing strain and the corresponding nonlinear increase in material damping in shear and constrained compression. Currently, there is total dependency on laboratory testing to evaluate these nonlinear properties. Highquality intact samples are often tested. Even with these samples, there is concern about the accuracy with which the laboratory results represent the in situ conditions. To begin to measure nonlinear soil properties in situ, a generalized test method is under development at the University of Texas at Austin. This method involves applying static and dynamic loads at the surface of a soil deposit using a truckmounted, electro-hydraulic shaker and measuring the dynamic response of the soil mass beneath the loaded area using embedded instrumentation. The resulting field test is a load-controlled dynamic test that induces nonlinearity in the soil. Initial testing has focused on vertically loading an unsaturated sand deposit, evaluating the magnitude of induced axial strains, and assessing the variation in constrained compression wave velocity. Vp, and constrained modulus, M, with strain. The nonlinear behavior measured in situ compares well with the general form of the nonlinear response in shear measured in the laboratory with intact specimens of the sand. Other comparisons are also presented to support the validity and feasibility of the field method.