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.
Analysis of the Ionospheric Effect for Time Offsets per GPS Code Measurements
This paper shows the analysis results of time offsets using P1, P2 and P3 code in GPS time transfer. The r2cggtts program has been used in GNSS Time Transfer and use the P3 ionosphere free combination of P1 and P2 code measurements. We modified the r2cggtts program in order to calculate and write all kinds of time offsets P3 as well as P1 and P2. The result of the modified r2cggtts program shows that time offsets using P1 and P2 are of wide distribution comparing to time offsets using P3. In order to Figure out the error factors for wide distributions of P1 and P2, we analyze and present the relation between the elevation angle and time offsets in this paper.