Applied Mechanics and Materials Vols. 477-478

Abstract: The advantages and disadvantages of the existing mathematical models to determine soft soil pre-consolidation pressure were compared. Based on the practical shape of e-logP curve, it is discovered that the Harris model is more fit to the e-lgP curve of soft soil in Dongting Lake area than the traditional cubic or quartic polynomial models. Besides, it avoids the impact of human subjectivity of Casagrande method effectively. Consequently, the Harris model was finally selected to calculate the pre-consolidation pressure of soft soil in Dongting Lake area by numerical method.

Abstract: Ten representative expressway pavement structures in the southern humid area were investigated, and then the stress state of subgrade soil under the pavement structure was calculated and analyzed by multi-layer elastic system theory. Based on the latest research results at home and abroad, combined with the stress and physical properties of subgrade soils in south moist and heat area, the laboratory test method for dynamic rebound modulus of subgrade soil in this area was determined.

Abstract: Based on the unsaturated soil ponding water infiltration test in laboratory, the influences of cohesive particles content, dry density and initial water content on infiltration rate are analyzed. Soil infiltration rate decreased with the increase of cohesive particles content and dry density; with the decrease of initial water content at low dry density, and with the increase of initial water content at high dry density.

Abstract: To investigate the influence of seasonally frozen ground on frost-heave force of artificial frozen wall, 6 artificial frozen wall model tests were performed with different temperature of seasonally frozen ground on developed test platform. Experimental data indicate that compared with the final horizontal frost-heave force of artificial frozen wall without seasonally frozen ground, it increased 8.6% and 9.1% with-3°C and-12°C seasonally frozen ground layer, separately, and it shows that there is an important influence of seasonally frozen ground on the horizontal frost-heave force of artificial frozen wall. It also can be concluded that the lower the temperature of seasonally frozen ground is, the less the freezing time is and the bigger the final horizontal frost-heave force is, but, among all the model tests, the freezing time that is taken to get a stable state is the most for the artificial frozen wall without seasonally frozen ground , and its the final horizontal frost-heave force is the smallest.

Abstract: Organic matter plays an important role in soil moisture variation. In order to know the effect of organic matter on soil moisture dynamics, this study compared the infiltration and evaporation of soils with different organic matter content. The results showed that increasing the organic matter content in a certain degree can suppress evaporation and infiltration of soil moisture, and hence improving water use efficiency. When the organic matter content reaches3.2%, effect of suppressing evaporation is most obvious.

Abstract: Due to the complication of grouting process in soil, design of fracture grouting works is still mainly based on empirical considerations and experiences from past projects. Based on the theory of particle flow, the domain of flow is defined by using Fish language implemented in PFC and the formulas for flow and pressure are put forward respectively. Combined with above study, the process of fracture grouting in soil is simulated with particle flow code (PFC2D) from micro-viewpoint under coupling environment. In addition, the emergence and development of crack and grouting pressure in soil is analyzed under different grouting pressure and soil properties. The research results show that pressure plays a key role in consolidating the soil by fracture grouting, but in fact it should be kept in a reasonable value in order to forming grouting slurry net entirely. Filed test indicates that fracture grouting greatly increases the bearing capacity of weathered rock in Xiamen Xiangan subsea tunneling and the conclusions of numerical simulation agrees well with the field test and grouting theory.

Abstract: Surface settlement and ground loss can be found inevitably and safety risk of pipeline underground is brought consequently due to excavation, no matter what kind of construction method is adopted. Grouting is increasingly used as the corrective measure to minimize the safety risk of pipeline underground, which means grouting in subjacent bed to raising the pipeline and keep settlement in control. Based on the project of raising an existing pipeline by grouting during the construction of the Huangzhuang station of Beijing Metro, general empirical formula and the finite-difference numerical simulation by FLAC are introduced to study the pipeline deformation caused by excavation, fracture grouting is designed in accordance with the factors mentioned above. The research results can provide references to the construction and design of raising pipeline by grouting in urban tunnel engineering.

Abstract: The computing of end-bearing capacity of pile has vital significances for foundation design while the foundations analysis is usually problematic due to those diverse soils and engineering conditions. Though various CPT-based methods which have already been applied in numerous huge engineering practices are available for the analysis of pile foundation bearing capacity home and abroad, there still seemed lacking legitimate guidance assisting to select these formulations quite effectively. In this paper, five CPT-based design methods are compared in deep, the realization through computer program is also presented, with the capacity data accumulated from pile engineering coming into mind, we are on the way to making designers choose better methods during the designing process.

Abstract: The problem always exist in foundation pit engineering that the support axial force can not be regulated in the pit system in real time.According to setting the axial force compensation system,the problem would be solved perfectly and efficiently,realizing the fact control and adjust the support axial force and stability. The axial force compensation system which is constituted by jacks distributed in the pit has been confirmed the significant role to control foundation pit deformation and internal force monitoring combined with practical engineering

Abstract: The O-cell test method which was applied on the pile load testing was introduced, including the basic principle, test device and test technique. Based on the project of offshore structure in Malaysia, the O-cell test was performed on the long rock socket bored pile. The bearing behavior and load transfer characteristics were analyzed. The shaft friction in the rock played an important role in the pile shaft friction. In some long rock socket pile, The O-cell method cant test the ultimate capacity of some long rock socket pile.