Abstract:Based on the principle of the dynamic substructure method, the mixed linear-nonlinear constraint modal method was proposed and applied to analysis of the two-dimensional nonlinear dynamic problem caused by the interactions between the foundation soil, box-type foundation, and upside shear wall structure under complex conditions. The complex conditions included the uniform viscoelastic boundary problem and the highly nonlinear contact problem between the foundation and surrounding soil. According to the local nonlinear feature of the soil-structure interactive system, the system was divided into several linear and nonlinear substructures. During the dynamic time history analysis, the self-compiled program based on second development was used to extract the equivalent characteristic matrices gradually for all the nonlinear substructures, which were combined with the linear substructures reduced by potential energy criterion-based truncation criterion. Then, synthesized modal processing was performed, and substructure equations considering the contact problem and involving the uniform viscoelastic boundary were deduced. Thus, a synthesized modal equation for each substructure was formed under the complex conditions. Results show that the dynamic response time history curves of the displacement, velocity, acceleration, horizontal shear force, bending moment, and interlayer displacement angle obtained by the mixed constraint modal method agree with those obtained by the ANSYS method, demonstrating that the mixed linear-nonlinear constraint modal method is an effective and feasible method of solving the soil-structure dynamic interaction problem under the complex conditions.

Abstract:To investigate the interfacial bond behaviors between fiber cement mortar and concrete with core drilling and pull-off tests, medium-sized columnar concrete samples enclosed with different strengths of polyvinyl alcohol fiber cement mortar, polypropylene fiber cement mortar, and steel fiber cement mortar were prepared. Core drilling and pull-off tests were conducted on the samples to obtain the pulling force with failure occurring at the interface, and the results of different kinds of samples from pull-off tests were compared with the axial tensile strength of concrete and compressive strength of fiber cement mortar. The results show that the interfacial bond strength between synthetic fiber cement mortar and concrete is higher than that between steel fiber cement mortar and concrete, and that the interfacial bond strength is positively correlated with the axial tensile strength of concrete and compressive strength of fiber cement mortar. There is also a linear correlation between the interfacial bond strength and compressive strength of fiber cement mortar.

Abstract:In order to study the soil disturbance and distribution characteristics of the additional stress induced by the penetration of soil samplers, based on the Geddes solution, this study obtained the solution of the vertical additional stress of soil at any location in the soil sampler induced by the end resistance and side resistance, and analyzed the distribution characteristics of the vertical additional stress of soil in the soil sampler induced by the end resistance and side resistance and the influence of the samplers parameters on the vertical additional stress of soil using a numerical method. The calculated results show that, during the penetration of soil samplers, the end resistance causes the compressive stress to change into the tensile stress in the soil, and the tensile stress does not vary with the soil sampler diameter and penetration depth. Increasing the diameter of the soil sampler can effectively reduce the additional stress of soil at the axis induced by the end resistance and side resistance, indicating that a larger-diameter soil sampler can significantly improve the quality of the soil sample in consideration of the effects of the end resistance and side resistance.

Abstract:In order to detect the voids and compactness around jacked pipes, a field survey and experiments were carried out to detect the voids around cement and steel pipes in an engineering case with a ground penetrating radar(GPR). A theoretical model for simulating the voids around the cement and steel pipes was established, and forward modeling of the GPR was conducted with the two-dimensional finite element method. The results show that the GPR is effective in detecting the voids around the cement pipes. However, it is not effective in detecting the voids around the steel pipes, because the multiply reflected signals between the radar antenna and pipe wall are strong. It is determined that it is feasible to use GPR to detect the voids around cement pipes. Meanwhile, for the detection of voids around cement pipes, new nondestructive examination methods and new types of equipment have to be developed in order to obtain better application effects.

Abstract:In order to examine the seismic mechanism of a new partially encased concrete(PEC)column(weak axis)-steel beam(reduced beam section)composite frame, a 1∶2 specimen of the inter-story substructure was designed and built. A test of the specimen was conducted with lateral low-cycle repeated loading. Based on the test observation and data analysis, the seismic performance of the specimen, including the failure process, failure mode, hysteretic property, lateral stiffness degradation, energy dissipation capacity, and deformation pattern, was analyzed. Test results show that the failure mode is primarily induced by the plastic hinge forming in the reduced beam section. The displacement ductility coefficients of the inter-story in the pushing and pulling direction are 3. 91 and 3. 97, respectively, and the maximum equivalent viscous damping ratio is 0. 359. The drift distribution of the specimen shows the ideal inverted triangle pattern of the flexure-shear type. When the load-carrying capacity of the specimen is decreased to 85% of its ultimate strength, the inter-story drift ratio is greater than 4. 9% and the minimum connection rotation is 0. 366 rad, which all surpass the lower limit(1/30)of inter-story drift at the maximum considered earthquake level, indicating that the specimen has high collapse prevention capacity.

Abstract:Based on seismic performance tests on four T-shaped recycled aggregate concrete(RAC)short-leg shear walls at a reduced scale of 1∶2, with different replacement rates of recycled coarse aggregate and axial compression ratios at low-cyclic loading frequencies, the variation patterns of the failure mode, characteristic curve, ductility, stiffness degradation, energy dissipation capacity, and characteristic loads in forward and backward directions are analyzed. The results indicate that T-shaped RAC short-leg shear walls show strong seismic performance, and can be applied to actual projects with a relatively low axial compression ratio; the performance of shear walls reflected by the characteristic curve and the indices, such as the energy dissipation capacity, gradually increase with the replacement rate of recycled coarse aggregate, and gradually decrease with the increase of the axial compression ratio; and the ductility of test specimens decreases in different degrees with the increase of the replacement rate of recycled coarse aggregate and axial compression ratio.

Abstract:Sinking of cement mixing piles has occurred in the treatment process of the soft soil foundation of an expressway in Jiangsu Province. Based on field data of the excess pore water pressure, earth pressure, and shear strength of the soil around piles, the mechanisms of the sinking of the mixing piles were analyzed, and methods for identifying the sinking are proposed. The field survey results show that the excess pore water pressure was larger than the earth pressure, and a phenomenon similar to liquefaction occurred in the soil around the piles when sinking occurred. This can be used as the identification criterion of the sinking of mixing piles.

Abstract:Major methods for determining a GPS receivers differential code bias(B), including the spherical harmonic function model and surface fitting model, have a high degree of computational complexity and poor efficiency. Based on the pseudorange data with carrier phase smoothing, global maps of vertical total electron content(V_TEC)of the ionosphere, and satellite B values provided by CODE, this paper proposes a new algorithm for determining the single GPS receivers B through interpolated V_TEC values from rotated maps and the pseudorange difference. The GPS receivers B values were estimated with the proposed method and observed data at IGS tracking stations, and were compared with those at the tracing stations provided by CODE. The results show that the new method can determine the GPS receivers B with an accuracy higher than 0. 4 ns.

Abstract:Using the annual WAVEFORM data of the Zhejiang offshore area from the SARAL satellite provided by AVISO, we analyzed the satellite waveform and proposed a new method of waveform retracking for offshore areas. With this method, a waveform was retracked according to its characteristics based on the physical mechanism. Through gross error elimination, collinear averaging, and comparison analysis of the waveform before and after retracking, we found that at 27° latitude around, the mean sea level drawn from raw data was 10. 770 m, and the standard deviation was 4. 515 m; the mean sea level drawn from retracked data was 12. 601 m, and the standard deviation was 1. 263 9 m. Around 30° latitude, the mean sea level drawn from raw data was 12. 236 m, and the standard deviation was 1. 877 m; the mean sea level drawn from retracked data was 12. 503 m, and the standard deviation was 0. 419 m. We compared the altimetry data with tidal gauge data, and obtained the following results: the mean difference between the raw data and tidal gauge data was 0. 275 m, and the standard deviation was 0. 273 m; the mean difference between the retracked data and tidal gauge data was 0. 046 m, and the standard deviation was 0. 049 m. The results show that the method discussed in this paper can greatly improve the accuracy and quality of satellite altimetry data.

Abstract:Using the GIS and DEM techniques, a distributed hydrological model based on a runoff generation theory(the Grid-Holtan model)was developed. For each computational cell, the infiltration-excess runoff was calculated with the Holtan infiltration method, and the overland flow and river flow routing were simulated with the one-dimensional diffusion wave model. The Grid-Holtan model, Shanbei model, and Xinanjiang model were applied to the Kongjiapo Catchment of the Qinhe Basin, in China. The results show that the Grid-Holtan model and Shanbei model perform better in flood simulation than the Xinanjiang model, while the flood peak simulation accuracy of the Grid-Holtan model is higher.

Abstract:In order to quantitatively study the impacts of underground mining on the water resources of the Kuye River Basin, the Mann-Kendall-Pettitt method was used to detect the abrupt change point of the annual runoff over the period from 1966 to 2009. The impacts of underground mining on runoff of the Kuye River Basin over the period from 1997 to 2009 and groundwater in the year 2009 were quantitatively estimated using the SWAT and SWAT-VISUAL MODFLOW models. The results show that the sharp decrease in runoff and the depletion of groundwater during the study period are mainly attributed to underground mining, which is responsible for 24. 20 mm of annual runoff reduction, accounting for 64. 16% of the total reduction, and 4. 09×10⁸ m³ of the groundwater affected.

Abstract:In order to improve the accuracy of precipitation interpolation and fully explore the information regarding precipitation variables, fuzzy entropy clustering(FEC)was carried out at rain gauge stations in a basin. A clustering validity function, based on possibility distribution and distance determination, was used to determine the fuzzy entropy coefficient and the number of clusters, so as to obtain the fuzzy clustering results and improve the original interpolation method. Based on data from 99 rain gauge stations located above the Bengbu Station in the Huaihe River Basin, cross validation was conducted under non-clustering and FEC conditions. The results demonstrate that FEC improves the precipitation accuracy in the inverse distance squared interpolation method.

Abstract:Aiming at detecting the concentrated leakage passage in a dam, an entropy weight-variable fuzzy set model for dam leakage detection was developed based on information entropy theory and variable fuzzy set theory. Using a dam in southern China as an example, the indices to be detected were determined first, followed by the weight of each index via the entropy weight method in the objective weight assignment method. Then, the comprehensive membership degrees of different borehole water samples to precipitation, leakage water, and groundwater, as well as the H value of each water sample, were obtained. Based on these values, the borehole water samples were classified and their origins were determined. The results show that there are four concentrated leakage passages in the dam, which accords with previous findings.

Abstract:In dike engineering projects for rivers and lakes, continuously heavy rainfall will lead to a significant change in the water level, which may cause safety hazards to dikes. To solve these problems, a water-gas two-phase unsaturated seepage model was used to analyze the saturated-unsaturated seepage of a dike under the coupled conditions of rainfall infiltration and water level change. Finite element simulation was performed to study the unsteady seepage in the processes of rainfall infiltration, water level rise in front of the dike, and coupling of continuously heavy rainfall and the water level rise. On these bases, anti-sliding stability analysis of the dike slope was conducted, with consideration of the effects of the dike water level changes, and the gas phase and matric suction during rainfall on the slope stability. The results show that, compared to the rainfall infiltration or the water level rise, the coupled conditions of rainfall and the water level rise will cause the seepage and slope stability of the dike to become more complex. Considering the gas phase and matrix suction will be helpful to slope stability analysis.

Abstract:In order to avoid the conventional methods requirement of selecting large quantities of input factors as well as its large errors in development of a dam seepage statistical model, problems caused by the need for many items to be considered in the earlier stage of model development, the copula entropy theory combined with partial mutual information was used to optimize the input factor selection. To obtain the copula entropy, the Gumbel function was used as the copula function, the Cauchy distribution was used to replace the normal distribution, and the Hample criterion was used to select the input factors accurately. This approach was applied to seepage detection for the Nuozhadu Dam. Comparison of the present results with those obtained from the conventional factor selection approach shows that the seepage statistical model for optimizing input factor selection based on the copula entropy has a better prediction effect.