Applied Mechanics and Materials Vols. 638-640

Abstract: Long-short composite pile is a widely used ground improvement technique. This study presents the results of finite difference analyzes using FLAC3D software to investigate the load-bearing and bearing mechanism of long-short pile composite foundation under rigid foundation. The pile-soil load-sharing ratio and stress ratio, axial force distribution in the piles, and pile side friction resistance distribution characteristics are also studied. The results showed that due to negative skin friction of pile in composite foundation soil functions are fully utilized. On the other hand, the load distribution between piles and subsoil is significantly affected by the cushion.

Abstract: Deep foundation pit engineer is characterized with high risk, and it is important to have a study on the risk management of deep foundation pit engineering. Risk Measurement, Risk Assessment and Risk Control of Deep Foundation Pit Engineering is very necessary. There is a need to establish a set of operational foundation pit engineering risk management system to comprehensively and accurately identify and measure the risks of deep foundation pit engineering; and conduct risk control on the basis of risk analysis. Using engineering testing technology, establishes a monitoring based deep foundation pit engineering risk management mode.

Abstract: The seawall shallow foundation is silty soil in northern coastal area. So the seawall is subject to ice load and freezing and thawing cycles as the temperature variation. It is unfavourable for the stability against sliding of seawall. The experiment of silt soil sample under freezing and thawing cycles has been done to analyze the law of mechanical properties. On this basis the numerical model of seawall with stability against sliding has been established. The calculation results show that the soil strength index decreased under ice load and freezing and thawing cycles. The stability against sliding of seawall would be reduced. Under ice load and freezing and thawing cycles the Mises yield stress reduced, horizontal and vertical displacement would be greater slightly. The stress of the plastic zone would be evenly distributed. The Plastic penetration area does not appear.

Abstract: This paper experiments on typical Malan loess, performs consolidated quick direct shear tests under different water contents by conventional direct shear apparatus, then analyzes the effects of water content on shearing strength parameters, namely cohesion and internal friction angle. The results show that cohesion decreases linearly as the water content increasing, and the relation could be obtained by data fitting. However, internal friction angle keeps basically stable with the increase of water content. Finally, based on the force analysis for micro particles, the changing rules of cohesion and internal friction angle with water content were deeply explained.

Abstract: Red sandstone with a strong water softening can cause difficulties of construction projects, especially for slope excavation and support engineering. Therefore, the study on the engineering properties of saturated red sandstone has a important meaning. The mechanical parameters of saturated red sandstone are obtained by the triaxial compression tests. The test results indicate that the ralations between peak strength, elasticity modulus and confining pressure for the saturated specimens are similar with the natural specimens, that is, with the increasing of confining pressure, the peak strength and the elasticity modulus will increase, but the growth rate becomes slowly. Under the same confining pressure, the peak strength and the elasticity modulus of saturated specimen are more smaller than the natural one. The mechanical damage caused by water recedes when the confining pressure increases, so for the geotechnical engineering with larger influence of water, the increasement of confining pressure by the supporting structures is conducive to the stability of rock mass. The research results will provide a theoretical basis for the red sandstone engineering.

Abstract: China is rich in hydropower resources that are mainly distributed in the southwest region. The continuous uplifts of Qinghai-Tibet Plateau in the recent hundreds of years result in geomorphologic landscapes of alpine valleys and complex initial geostress field. Constructing large-scale underground cavern groups in such complex geological conditions will lead to some prominent problems. In particular, the unloading and relaxation deformation of rock masses has become one of the key technical problems that restrict the design and construction of underground caverns in southwest China. Based on the engineering practices of hydropower construction in southwest China in recent years and actual engineering geophysical prospecting detection results, typical unloading relaxation characteristics of underground cavern surrounding rock under high geostress are summarized and analyzed. Differences between areas are analyzed and arranged for the rock unloading relaxation area. By reference to the qualitative classification table for the rock mass intactness in the GB 50218-1994 Standard for engineering classification of rock masses, a standard classification methodology for unloading relaxation areas of rock masses under high geostress is initially formed, which is of great significance to the design and construction of underground caverns under high geostress.

Abstract: Through studying the field test results of rigid core pile composite foundation, Analyzing dynamic characteristics and dynamic response from peak acceleration and frequency duration, peak velocity and seismic waves. The following conclusion were got: Along with the rising of the upper load, peak acceleration of rigid core pile decrease, The frequency of Rigid core pile was between 6Hz-44Hz, Peak rate in the bottom of core pile have obvious change.

Abstract: The calculation for the gravitational settling and position of a sunken ship can provide important information for a reasonable salvage program. A 3D elastic-plastic dynamic finite element model was established to calculate the gravitational settling of a sunken ship in soft foundation of Tianjin port in China. The results showed that a large amplitude settlement had happened in previous seconds, and then settlement tended to be stable. The stable value was in keeping with the field observation value. Besides, a collapse pit on the top surface of soils under the hull induced by the gravity of dredge was formed while soils around the compression region were raised. Moreover, the strain value increased rapidly in previous seconds which induced a large amplitude settlement of the ship and then tended to be stable.

Abstract: Yueliangwan Reservoir dam foundation there is fault fracture zone,silty sand layer geological and so on defects,dam foundation of inhomogeneous deformation and seepage problems is the key of the dam foundation treatment.Basis on conducting detailed geological surveying,to take remove foundation,consolidation grouting and replacement process measures to for engineering geological problems of the dam,effectively solve the inhomogeneous deformation and dam foundation seepage problems.

Abstract: Dismantling the inner support of deep foundation pit is a risk point.It is of great importance to guarantee the safety of foundation pit when removing the inner support, and the deformation monitoring and analysis in the process of dismantling inner support is crucial. In this paper, a super deep foundation pit engineering as the research background.Through monitoring and analyzing the law of a deep horizontal displacement of the supporting structure,ground settlement, vertical settlement and axial force of support in the process of support demolition,which can be obtained that: the settlement of surface ground around the foundation shows spatial and temporal clearly and the distribution of deep horizontal displacement of supporting structure is similar to the parabolic which the maximum point constant upward shift with supporting continuous removed.Soil pressure of supporting shared with support removing process is changing, and the earth pressures support sharing is increasing. From the monitoring results, the demolition scheme is reasonable and effective and meets the requirements of design and environment.