Applied Mechanics and Materials Vols. 90-93

Abstract: The effect of anchor on fractured rock specimens in splitting test is simulated by DDARF method in this research. The results are compared and agree well with laboratory test results. The DDARF program is also adopted to analyze the stability of an underground cavern with four groups of randomly generated joints in the surrounding rocks, in which two conditions with and without rock bolts are considered. Besides, the crack propagation process around the cavern and the displacements of key points in the surrounding rock are monitored and applied to investigate the stability of the cavern.

Abstract: Support invalidity of a roadway have a largely influence on production safety of coal mines, especially the soft coal roadway, which deforms heavily. To solve this problem, it began from the gateway section optimization, based on the actual geological condition of Chang-gouyu Mine. The computational model was established up to optimize tunnel shapes using FLAC^3D. The scopes of plastic zone, stress field, displacement field were compared and analysed for different shapes of roadway. The irregular trapezoid section is adopted, then the bolt support parameters were designed and field application was done. By using the irregular trapezoid, the stress distribution around the roadway is improved and the deformation and plastic zone is decreased. Under the geological conditions of the soft coal seam and hard roof strata, the stability of roadway was effectively controlled by using optimized trapeziform cross-section and bolting support.

Abstract: By a circular increment step load and unload method, a set of rheological experiments were performed to study the creep properties of amphibolite and the deformation data of instantaneous elasticity, instantaneous plasticity, viscoplasticity and viscoelasticity could be obtained. The results showed that: the creep threshold of amphibolite(σ_s1) was 25.46MPa; whenσ_s1s2, the proportion of plastic deformation in the total deformation was very small and the value of creep deformation always tended to a stable value; whenσ>σ_s2, the rock samples failed rapidly and had no obvious creep. According to the creep and failure properties of amphibolite, the generalized Kelvin creep model was acted in series with the Mohr-Coulomb criterion and a modified generalized Kelvin creep model was built and the corresponding visco-elasto-plastic constitutive relationships were deduced. The modified model could simulate visco-elasto-plastic deviatoric behavior and elasto-plastic volumetric behavior. The model parameters of amphibolite were fitted according to the data of rheological test. The testing curves were coincident well with the theoretic curves by comparison which showed the creep properties and the plastic flow of hard rock could be well simulated by the generalized Kelvin creep model.

Abstract: Banqiao school building had to be demolished for rebuilding because of severe damage induced by liquefaction following the 2008 Wenchuan Ms 8.0 Earthquake. The mechanism of the building damage and the characteristics of liquefied soils were investigated by trench, borehole drilling, and Dynamic Penetration Test. The detailed field investigation and in-situ tests show that: (1) The Banqiao school building suffered more severe damages than its surrounding buildings from the liquefaction rather than inertia force of shaking during the earthquake; (2) The subsurface liquefied soils are gravelly soils at the depth of 3.0 to 6.1m, which are significant different from the ejected fine sands; (3) It is unreasonable to regard gravels as non-liquefiable soils and a new procedure for gravels liquefaction evaluation need to be developed.

Abstract: In order to study the dimensional influence of tunneling on adjacent pile foundation, successive segmental excavation is simulated considering the geological background in Nanning. The different stiffness ratio of pile and soil is obtained by changing the pile’s elastic modulus, radius or length. The additional displacement and inner force due to tunneling are compared for different stiffness ratio. Many useful conclusions can be drawn. Foundation settlement occurs on the top of the tunnel while upheaval arises below the tunnel. The range of influence is enlarged with the distance from tunnel. Pile foundation is influenced obviously in the area of 1.5 times tunnel diameter from the tunnel face. The additional displacement changes clearly with different stiffness ratio, especially the vertical settlement. The conclusions will be useful for the construction and design of tunnel.

Abstract: Based on the recent 20 years' observation and research, this paper briefly discusses the mechanism of forming, mechanical properties of coastal saline soil and the main factors which bring the important influence to buildings. Some reasonable comments on design and construction of the work in this area are put forward.

Abstract: At space compacted, pipeline-intensive, buildings and underground structures adjacent places, environmental deformation is sensitive to deep pit excavation, so deformation as well as slope stability is the control factors for safety. With FEM and automatic remote monitoring, the deformation of adjacent metro in operation was analyzed during the deep pit excavation; acquired results showed deformation caused by pit construction met the requirements of metro tunnel structure less than 4mm.

Abstract: In China high-speed railway engineering practice, embankment settlements calculated values were often greatly different to the measured values, which may result from the stresses distribution under the embankment usually simplified. According to this issue, the elastic embankment method was introduced, the stresses under various embankment were calculated, the influence factors of the stresses values and distribution were analyzed. The stresses calculated by elastic embankment method, proportional load form and uniform load form were compared with the measured stresses. The relationship among the four kinds of stresses was analyzed. The applicable conditions of the various calculation methods were put forward. If the ratio of embankment half surface width and height was less than 4.5, when the stresses calculated by uniform load form were multiplied by correction coefficient 1.15, they were tallied well with the measured stresses.

Abstract: Using DDARF method, the uniaxial and biaxial compression experiments of double-fractured rock samples are numerically investigated. Influences of different fracture angles and confining pressures on behaviour of rock samples are studied. Moreover, the fracture process, the crack initiation stress, and the peak strength of the fractured rock under both uniaxial and biaxial compression tests are obtained. The results are used to obtain the strength envelope and to analyze the rock stability of an underground project as a case study.

Abstract: Using coupling model, the time-effect behavior for deep pit during excavating and dewatering is studied. The distribution of the seepage field, the horizontal displacement of wall, the settlement of surrounding soil and the settlement of the road are all obtained from the coupling analysis. Taking the deep foundation pit engineering of one station as engineering background, the coupling of seepage and consolidation is simulated in the process of excavating. According to the comparative analysis between the simulation value and the measured results, it can be known that the calculation value considering the coupling of seepage and consolidation is well in accordance with the measured value. The analysis shows that the provide method can be used to simulate the deep foundation under the coupling effect and it is reasonable, feasible, and can provide some kind of references to design and construction.