Applied Mechanics and Materials Vols. 256-259

Abstract: The hypothesis on effective stress of unsaturated soils is validated by consolidation strength results of triaxial tests for the compacted residual soil. The effective stress can describe the unsaturated soil behavior, which was defined from shear strength or from soil water characteristic curves. Since the effective stress from consolidation agrees with that from the shear strength, the effective stress from soil water retention curve could describe the unsaturated behavior consistently on both consolidation path and stress at failure. The effective stress can describe the entire unsaturated behavior from consolidation to failure.

Abstract: In order to decrease the environmental impact caused by Portland cement in binders for soil stabilization, Zeolite was chosen to replace some percentage of Portland cement. Unconfined Compressive Strength (UCS) was used as a recognized parameter for assessing the performance of soil stabilization. The UCS values of the Zeolite-PC mix in three binder dosages (2.5%, 5.0% and 10%) and at three curing periods (7 days, 28 days and 90 days) were for two model soils; namely a gravel sand and a clayey silt. The experiment results demonstrated that the highest UCS value 1.28MPa, of Zeolite-PC mixes was obtained at 90 days, in a 10% content binder dosage, which has exceeded the current USA guideline of 350kPa, comparing all of the UCS values for all dosages and all curing periods in clayey silt. The highest UCS value of 7.65MPa for Zeolite-PC mixes was achieved at 90 days and in a 10% content binder dosage in gravel sand. In comparison, the PFA (Pulverised Fuel Ash)-PC mixes have presented lower UCS values than the Zeolite-PC mixes with the same content ratio and the same testing time.

Abstract: The cyclic behavior of stratified sands interlayered with silt is at present poorly understood, although stratified sands exist for various soil deposits and hydraulic fill, which have a history of liquefaction during earthquakes. The main objective of this research project was to compare the cyclic behavior of stratified and homogeneous sands for various silt contents. A comprehensive experimental program was undertaken in which stain-controlled undrained cyclic triaxial tests for stratified sand samples interlayered with different thickness silt were performed. The silt thickness ranged from 0 to 80mm was considered. The confining pressure in all test series was 100kPa. The results indicate that the thickness of the silt seam sandwiched in the sand samples has a significant influence on the liquefaction resistances of layered sands. In other words, there is a critical thickness of silt seam that the saturated stratified sands have a critical shear strain. This finding justifies applying the laboratory tests results of homogeneously reconstituted samples to the field conditions for the range of variable studied.

Abstract: Dry jet mixing pile is the general technique of composite ground consolidation , which is used in foundation treatment of soft soil under highway. It has a widespread applying due to so many advantages. This passage adopts an example of dry jet mixing pile combined with Longkou Shugang expressway engineering, it aims to state that dry jet mixing pile consolidating foundation along intertidal zone would obviously improve bearing capacity, strength and compressive modulus of foundation soil, reduce settlement and make a difference of consolidating foundation in according to data analysis of field or laboratory experiment. This technique is an effective way to solve the Jump Car problem and economic and quick.

Abstract: With the deepening of China's urbanization, the urban construction land in the mountainous areas is becoming increasingly tense, more and more bulidings pile had to be built on the hillsides. The pile is not only as foundation, but also have the role of reinforcement slope, its mechanical property is complex more than the anti-slide pile and ground piles under lateral load. Now the analysis against its bearing characteristics and deformation mechanism are not perfect, carrying out a thorough and meticulous research review is necessarily. Based on the review of current study on pile under icomplex loads, the present study provides a train of thought for further research on the behavior of pile under complex load.

Abstract: Taking one foundation project as an example, a series of tests are carried out to study the dynamic compaction parameters and its effects on the deep collapsible loess foundation under super high fill in Lvliang region. Analyses are made on the average settlement of each test area before and after dynamic compaction and on the regularity of the main physical and mechanical indexes of soil. At the energy levels of 2000 kN•m, 3000kN•m and 6000kN•m, the main parameters are gained, such as the effective reinforcement depth, the centre distance of tamping points , the standard of stopping ramming, and the optimal ramming number; hence, the empirical formula of the effective reinforcement depth of dynamic compaction. The results of the tests show that the deep collapsible loess foundation in Lvliang region can be effectively reinforced by dynamic compaction, that the stability of foundation is good, and that the loess collapse in the reinforced range is eliminated basically. Moreover, after dynamic compaction above the energy levels of 2000 kN•m, the eigenvalue of the bearing capacity of collapsible loess foundation in Lvliang can reach over 300kPa; the deformation modulus of foundation soil is more than 25MPa. Therefore, the results of the tests can provide a reference for the design and construction of projects of the same kind; it can also provide a reliable basis for relevant norms and standards.

Abstract: A series of moisture content tests were carried out to study the changes in geogrid-reinforced clay moisture content under freezing-thawing cycles, the influences of compaction degree, reinforcement layers and initial moisture content of the soil on the soil moisture content under freezing-thawing cycles were discussed. We can see that the soil compaction degree is the first important factor to the moisture content, the change of upper lay clay moisture content is positive for the low compaction degree and negative for a high one; the reinforcement layers is the second important factor to moisture content, the upper lay moisture content reduces with the increasing of reinforcement layers, it is significant in the high compaction soil; the initial moisture content is the weakest factor, a big change of upper lay moisture content only appears when the initial moisture content is large and the soil compaction is low.

Abstract: Centrifugal shakers are widely regarded as state-of-the-art testing facilities of geotechnical earthquake engineering for providing an effective solution for the unequal gravity stress between models and prototypes typically in traditional test methods. Currently only two large centrifugal shakers are in the United States and Japan respectively, whereas no one has been established in China. Such situation remarkably lags behind the serious seismic conditions and the world largest construction scale of civil engineering in China. Due to the lack of experiences and the lot of difficulty, one significant task of large scale centrifugal shaker construction is tracking study on the world advanced facilities. The paper outlines the technology parameters and components of the two existing large centrifugal shakers. Through investigating and comparing the structural characteristics of the two facilities, the differences between the two are summed up and analyzed. The analyses indicate that key technologies mainly centre upon centrifuge arms, centrifuge buckets, exciting devices, power sources and guide-support devices. The results can provide assistance and reference to the construction of foreign and domestic large scale centrifugal shakers.

Abstract: By summarizing and comparison of methods for evaluating the scale of fluctuation, suitable and convenient method to calculate correlation distance is obtained. The space averaged method is employed to analyze the scale of fluctuation of soil in the vertical direction of Tianjin combining geology data, and regional representative values are obtained, which is of high application value on risk assessment and reliability analysis in geotechnical engineering.

Abstract: The basic characteristics of the cement-sodium silicate grout were researched. Viscosity tests were performed. The viscosity curve and temperature curve with time were obtained. The change law of viscosity was analyzed. According to the varying characteristics of grout viscosity, the process was divided into three stages: low viscosity period, the growth period and curing period. solidification tests were carried out for cement-sodium silicate grout with different temperatures, densities and water-cement ratios. Three parameters affected the initial setting time of the grout significantly.