Test on Mechanical Properties of Cemented Soils Using Secondary Development Data Acquisition Test System
A secondary development of computer aided data acquisition test system is performed in order to improve the disadvantages of original system. In this way, the qualified influences of cement content and curing time on yield strength and stiffness of soil can be automatic acquisition in consolidated undrained triaxial tests. The data collected from the system show that the deviatoric stress of soil increases with increasing axial strain initially followed by a relatively smooth decline after yield point. Yield strength increases with increasing cement content and curing time at the same strain. A well-defined linear relationship between yield strength and cement content are observed and also the relationship between yield strength and curing time. Finally, a linear function is defined to express the linear relationship between yield strength and those two factors and corresponding linear coefficients are obtained through a multiple regression analysis of test data. Stiffness of specimens shows an initial sharp degradation followed by smooth attenuation with increasing axial strain. The addition of cement and long curing time can effectively improve the stiffness of specimens especially at low strain areas.
Experimental study of triaxial test of soils stabilized by cement mortar
In order to study the features of shear strength of soils stabilized by cement mortar,to provide a theoretical reference to rationally determine the engineering application ratio of soils stabilized by cement mortar,some CU triaxial tests are performed on the soils stabilized by cement mortar,based on the four aspects: sand content,cement mixing ratio,water content of raw soil and sand diameter.It is shown that the mixed sand can improve the strength of stabilized soils,in general,the effective cohesion increased and then decreased with the amount of mixed sand increased,the turning point of the doped amount of sand is the best amount of mixed sand(about 10%),while effective friction angle increasing continuously.The cement mixing ratio increasing can effectively improve the strength of stabilized soils under a certain amount of mixed sand;as the water content increasing,cohesion of stabilized soil appears as linear decrease relationship approximately;while the internal friction angle remains almost unchanged;and when using cement mortar in the treatment of high water content of soft ground,the appropriately increasing the volume of mixed sand can more sharply improve the mechanical properties of stabilized soil.When the admixture ratio fixed,sand diameter can influence the shear strength of stabilized soil to some extent.In general,the shear strength of stabilized soil is higher when it using the sole sand diameter;and uniformity coefficient Cu tends to the largest,coefficient of curvature Cc tends to the minimum with the sole particle size and good gradation of stabilized soils.
The effect of collimation on image quality and radiation safety in digital radiography of small animals
Collimating the primary x-ray beam to the specific area of anatomic interest has traditionally been strongly recommended to produce high quality radiographic images, even though some small animal patients can fit their entire torso on a single radiographic casette or detector. However, modern digital radiography may allow for whole-body projections for these patients at similar quality to specific collimated projections. Lateral and ventrodorsal projections of 31 small dogs were obtained to evaluate the effect of collimation on the quality of the resulting digital radiograph. Each projection was performed using both a collimated and whole-body technique. Scatter radiation was detected during each exposure as well to determine the effect of collimation on radiation safety for veterinary personnel. The resulting images were cropped to portray only the thorax, and were evaluated by five radiologists blinded to the procedure used for each image. Visual grading characteristics analysis was performed. An overall trend towards higher image quality was found in the collimated approach compared to the whole-body, but in most cases this change was not significant. Overall image quality for the ventrodorsal images was found to be significantly better in the collimated approach compared to the whole-body. Evaluation of image histograms suggests that the application of digital processing and the look-up table differs between them, and this may account for a large portion of any quality difference. Over twice as much scatter radiation was detected during the whole-body images as during the collimated images. Overall image quality was rated as adequate to high for almost all images with both approaches. Adequate collimation remains recommended to provide the highest quality images with the lowest exposure to veterinary personnel.