Advanced Materials Research Vols. 250-253

Abstract: Guangxi province is the typical expansive soil area, and the unconfined compressive strength is the important strength index. There is little studied result about the unconfined compressive strength of expansive soil in Guangxi province. Based on the expansive clay experimental embankment of Nanyou Highway, the experimental research on the unconfined compressive strength was undertaken. Tests results indicate that the expansive clay samples are all disintegrated when the sample is dip in water, which show that the stability of expansive clay is very weak. Some lime improving samples of curling 7 days and 14 days are also disintegrated when dipping in water, which indicate that the unconfined compressive strength sample of lime improving expansive clay should curl 28 days. Lime ratio and curing time both influence the unconfined compressive strength of improving expansive clay greatly. There is optimum adding lime ratio for lime improving expansive clay. During the early days of curing the unconfined compressive strength have linear increase with curing time.

Abstract: One kind of slurry with low permeability coefficient and certain adsorption and retardation to pollutants in leachat is developed in anti-seepage engineering of leachate for domestic waste landfill site. Through the orthogonal experiment, the selected optimal formula of the slurry with a bentonite base is: bentonite 20%~30%; cement 15%~25%; fly ash 20%~25%; Na₂CO₃ 1.0%~1.4%; diluent FCLS 0.35%~0.75%; and etcaeteras is water. Concretion stone ratio of this slurry is greater than 99.6%; concretion body 28 day permeability coefficient is less than 0.8×10^-7cm/s, unconfined compressive strength is less than 2.0MPa; elastic modulus is 50～800MPa. The slurry concretion body’s hindered COD, BOD, NH₄-N and phosphorus adsorption rates reach upper 82%, block rate reaches upper 99% to Hg, Pb and other heavy metal ions. The slurry concretion body’s permeability coefficient is low, and its adsorbed or blocked function to landfill site leachate is very well. Meanwhile, it has considered reducing the compressive strength and brittleness of the concretion body, enabling it to have certain plasticity and toughness adapted for the distortion of the base for domestic waste landfill site.

Abstract: The technical measures of dynamic consolidation used in silt soil foundation reinforcement of a seaside project in Hainan province were introduced. According to plate loading test and heavy dynamic penetration test, the effect of dynamic consolidation treatment was analyzed and evaluated.

Abstract: In order to make good use of large-span suspension bridge health monitoring system, the design for Wuhan Yangluo Yangtze River Bridge health monitoring system(YLBHMS) is outlined, and the implementation of the deformation and vibration on-line monitoring system is introduced. Analysis of the measured temperature, the vertical deformation effect of the main cable and the girder, the longitudinal deformation effect of the main tower and the girder, The fingerprint files are accumulated for the assessment of temperature deformation, the work state of bearing and expansion joints in the follow-up operation; The vibration system recorded the Wenchuan earthquake response, the analysis of the bridge vibration response concluded that the bridge seismic response is in the design scope, the work state of the bridge did not change after the earthquake.

Abstract: The detection meaning of section outline on highway tunnel and the principle and operation method of laser measuring instrument of tunnel section are introduced in this paper; Aiming at the quality inspection and evaluation content for highway, the laser measuring instrument of tunnel section is used to inspect the geometry of tunnel outline. The inspection data on axis deviation, width, vaults height and arch waist height of tunnel are obtained by calculation of polar coordinates and cartesian coordinates gotten by instrument scanning. Compared the inspection data with design data, we can judge whether the tunnel meets the requirements. According to this method, the tunnel outline of Sai-Guo highway meets the basic requirement.

Abstract: Through model test, the displacement of the top of the wall and the strain of the core pile with excavating were measured and the deformation and damage characteristics of the soft soil foundation pit supported by SMW was revealed. By parameter sensitivity analysis and back analysis, ABAQUS was applied to build the numerical simulation model of SMW in soft soil and the model parameters were obtained and the model was optimized. The impact of the embedded depth on the displacement of the top of the wall ,strain of the core pile, the bending moment of the core pile and the surface subside were systematic studied. The curve fitting equations of the above mentioned action effect variables with embedded ratio were obtained. Studies have shown that embedded depth was significantly influenced the working properties of SMW. When the embedded ratio reaches a critical value, the nonlinear variation characteristics of the above mentioned action effect variables will occur and the signs of foundation pit's failure will occur.

Abstract: The surface shape of structure plane is closely related with its mechanics property. Precise measurement to the surface shape of structure plane is the basis of deformation mechanism and strength characteristics. On the basis of studying advantages and disadvantages of the measuring instrument, the author has developed a new kind of portable measuring instruments innovatively - Contact Punching Device which has improved open-air working efficiency greatly. Application results show that JRC obtained by the Contact Punching Device is very close to the actual JRC of surface shape of the structure plane. Then about size effect of rigid structure plane, got the following principle that the statistical variance of the undulating roughness of the structure surface decays gradually with length of the rock sample, and got the limiting length of the undulating roughness when the influence of shearing intensity of the structure is dispelled. Finally, which proved through the embodiment of different rock and different weathering rock, the result indicates this method can be applied to engineering.

Abstract: From the damage investigation of Ning’er earthquake and Wenchuan earthquake, it was found that the damage of arc-shaped wall was severe. The seismic response analyses indicate great differences in basic mechanical properties between arc-shaped wall and unarc-shaped wall. Because of stress concentration in the corner of arc-shaped wall, it is easy to exceed the limits of brick’s intensity, in addition, brittle failure of brick would happen. So arc-shaped wall should be used less in the areas where earthquakes are a common occurrence.

Abstract: The chloride ingress of prestressed concrete should consider much more factors than common reinforced concrete. And the prestressed concrete covering layer system is a complex system which includes not only the non-uniform layer of concrete, but also the non-prestressed reinforcement, the metal corrugated pipe and the cement paste incrustation body in the pipe. Taking into consideration of the effect of stress level in concrete and the non-prestressed reinforcement, the multi-factors for chloride ingress corrosion model is achieved and the durability limit state equation for prestressed concrete structures is established. The paper presents a determination method for the depth of the covering layer system of prestressed concrete structure in marine environment. The principle for zonation of the prestressed concrete covering layer system’s minimum depth is established after sensitivity analysis of the effect factors in the marine environment, and the environment temperature and humidity are identified as the main environment sensitivity factors for the depth. Therefore, the paper also proposes zoning method and the division regions for the prestressed concrete covering layer system depth of the coastal region in China.

Abstract: The interaction mechanism, between soil and U-shaped Subway tunnel, is studied by numerical simulation in the environment of ground fissures. The Subway Line 2 through the ground fissures in Xi’an. The analysis results show that the soil mass influenced by the relative displacement and the vertical displacement gradually increases with the relative displacement increasing of ground fissures movement. The deformation area of tunnel lies in the two sides of presupposed ground fissure, and the area enlarge with vertical relative displacement increasing. The tunnel structure damages at the ground fissures when the relative displacement reaches to 100mm. The footwall part is in tension and the hanging wall part is under pressure on the top of tunnel structure at the ground fissure. The footwall part is under pressure and the hanging wall part is in tension on the bottom of tunnel structure at the ground fissure. In the practical projects, the sectional type tunnel should be employed when the Subway tunnel through the ground fissures.