Abstract:Using full stress and multi-field coupling triaxial apparatus, the hydro-mechanical coupling triaxial compression drainage tests were carried out on saturated granite with different loading rates, confining pressures and pore pressures. The stress-strain curves of saturated granite under different loading rates and effective confining pressures were provided respectively, and the variation rules of peak strength, peak strain and elastic modulus were studied under the very loading rates and effective confining pressures. The results show that:(1)under the effect of different effective confining pressures and loading rates, stress-strain curves of saturated granite exhibit the nonlinear compaction, elasticity, yield and failure stages. At the initial stage of deviating stresses loading, the nonlinear compaction stage is relatively obvious, but with the increase of confining pressure, the nonlinear compaction stage gradually disappears. Due to the high density of granite, the linear elastic stage of the curve is long and relatively smooth. In the yield and failure stages, the rock shows obvious brittle-ductile transformation process.(2)The peak strength of saturated granite increases with the increase of loading rate, and when the effective confining pressure is constant, the peak strength is approximately equal, and the resistance to external load is roughly the same.(3)Under the condition of slow loading, the loading rate has obvious strengthening effect on the peak strain of saturated granite, while the strengthening effect is limited. When the effective confining pressure is constant, with the synchronous increase of confining pressure and pore pressure, the peak strain presents an increasing trend.(4)Elastic modulus and loading rate show a quadratic polynomial growth relationship. However, with the synchronous increase of confining pressure and pore pressure, the elastic modulus presents a decreasing trend.

Abstract:The rocks of TBM hole excavated material were used as the source of coarse aggregate of concrete. Two kinds of aggregate gradations were designed and five water-cement ratios of 0.55, 0.60, 0.65, 0.70 and 0.75 were used to study the compression strength of TBM concrete. The experimental results show that the compression strength of TBM concrete is less than that of ordinary crashed stone concrete at the same water-cement ratio, And with the increase of water-binder ratio, the compression strength of TBM concrete decreases more than that of ordinary concrete. In addition, in the range of water-cement ratio of 0.55 to 0.75, the relationship between the compression strength of TBM concrete and the water-cement ratio is a linear function with negative correlation. Besides, the rational use of Talbot formula is instructive to aggregate gradation of TBM concrete.

Abstract:In order to explore the relationship between damping performance, compressive strength and splitting strength of brick-rich recycled concrete and sanding ratio, 6 groups of regenerated concrete beams, compressive strength and splitting specimens with different mix ratios of 25%~50% were designed by selecting the whole regenerated coarse aggregate rich in brick particles and taking the sand rate as the research parameter. The effects of sand ratio on the damping performance, compression resistance and splitting strength of brick-rich recycled concrete beams were studied by experiments. The results show that with the increase of sand rate, the compressive strength and splitting strength of brick-rich recycled concrete decrease, while the damping ratio increases first and then decreases slightly with the increase of sand ratio.

Abstract:Marshall Test was performed to find out how to improve the application effect of asphalt mixture. The effect of two types of fibers with different contents on Marshall Index was investigated to determine the laws of influence on relevant indexes. The results show that the optimal usage of conventional asphalt mixture is proportional to the amount of fiber added. Specifically, the optimal usage increases with the amount of fibers added. However, when the amount of fibers added exceeds one threshold, the optimal usage remains unchanged. The more the fibers are added, the more obviously the mixture density decreases and the voidage increases. The stability and flow value of mixture increases as the two types of fibers are added. In particular, the stability and flow value undergo a significant increase when the polyester fiber-reinforced mixture is added.

Abstract:In order to reduce the engineering cost of muck improvement during the process of the excavation of Earth Pressure Balance (EPB) shield in composite stratum, based on the project of Guangzhou metro line 21 from Zhucun to Xiangling, the particle size distribution curve of composite stratum was calculated by particle analysis of different proportion combination residual soil of silty clay and gravel sand in this paper. Besides, combined with laboratory test and field test, the flow state and permeability of mixed residue soil were studied. The results show that when there is silty clay layer in the composite stratum, the flow state and permeability of the coarse-grained soil muck are greatly improved. Adding a small amount of bubbles or bentonite slurry, the muck state can meet the requirements of shield tunneling. When the content of silty clay is between 30% and 70%, the slag can reach a good plastic flow state. When the content of silty clay exceeds 70%, there is a risk of mud cake.

Abstract:The impact of the variation of shear strength parameters of soil with depth on the stability of buried foundations has not been thoroughly studied yet. A non-stationary random field model in which the mean and standard deviation of undrained shear strength of soil increase linearly with depth with different degrees was established. In addition, the stationary random field with the same mean of undrained shear strength as the corresponding non-stationary random field was established. The influence of non-stationary random fields with different degrees on the bearing capacity of buried foundations and the failure probability of buried foundations were discussed. The difference of bearing capacity associated with non-stationary random field and its corresponding stationary random field was compared. The results show that when considering the non-stationary of undrained shear strength, the mean value and the difference of bearing capacity of buried footings increase linearly with the degree of non-stationary. The deeper the foundation depth is buried, the more the average bearing capacity increases with the increase of non-stationary degree. Under the same safety factor level (FS >1), the failure probability of the foundation increases with the increase of non-stationary degree. For the buried foundation, at the same level of safety (FS >1), the stationary stochastic field model underestimates the failure probability of a non-stationary field, and the higher the non-stationary state, the larger the estimation error.

Abstract:Based on the deep foundation pit project of Hongqiao Station of Nanjing Metro, combined with the monitoring and measurement data of the foundation pit in the process of soil excavation, FLAC 3D software was used to establish a three-dimensional numerical simulation model of the deep foundation pit of the station so as to simulate the excavation and support dynamic construction process of the foundation pit. In addition, the deformation calculation results and monitoring data of the numerical simulation were compared. The research results show that:(1) the horizontal displacement of the diaphragm wall is in the range of the wall body, approximately in the shape of parabola. With the excavation of the foundation pit, it increases nonlinearly, and the peak value of displacement appears near the excavation working face of the foundation pit. (2) The influence of the surface soil by the excavation of the foundation pit is mainly in the range of 1H (H is the depth of the foundation pit), and the settlement curve under different working conditions is approximately parabola, and the peak value of settlement is linear Increase; under the same working condition, the displacement value of monitoring points at different positions presents a process of continuous redistribution over time, but the overall curve is still "concave". (3) The amount of foundation pit uplift is also related to the excavation process of foundation pit, the maximum uplift of soil occurs near the central axis of foundation pit, and the amount of uplift increases nonlinearly with the increase of excavation depth. (4) The erection of support can play a positive role in the deformation of the retaining structure and the settlement control of the soil mass, and the delayed erection of the support is extremely unfavorable to the development of the deformation.

Abstract:In order to study the influence of rainfall on slope deformation and monitoring point arrangement, the finite difference-strength reduction method was used to calculate slope deformation under different reduction coefficients and rainfall intensity. The correlation degree between deformation of monitoring points and reduction coefficient can be obtained by using grey theory analysis, which can realize the optimization of slope deformation monitoring arrangement, and a monitoring point optimization arrangement plan was formulated according to an actual project. The results show that the slope is more possible to behave shallow failure due to rainfall. The application of grey relational degree in engineering can avoid the unnecessary monitoring points and make the monitoring data more conducive to guiding the warning work.

Abstract:In this paper, Duncan e-b model and elliptic-parabolic double yield surface model were respectively used to analyze the finite element stress and deformation of the rockfill dam with two diversion river core walls, thus comparing the difference in stress and strain of the dam calculated by the two constitutive models during the full storage period of normal high water level. The results show that:(1) the settlement calculated by the two models is relatively close, and the maximum settlement calculated by Duncan e-b model is slightly smaller. The horizontal displacement along the river calculated by Duncan e-b model is larger than that calculated by the double yield surface model. (2) Influenced by the arch effect of the heart wall, the principal stress in the heart wall is smaller than that in the transition layer, the minor principal stress is positive, and no tensile stress appears in the heart wall, no matter in the Duncan e-b model or the double yield surface model. Compared with the double-yield surface model, the stress calculated by Duncan e-b model is more obviously affected by the arch effect. (3) The small principal stress of cut-off wall in full storage period appears tensile stress at the left and right bank corners. The distribution law of the tensile stress area calculated by the two models is basically the same, but the value and gradient of the tensile stress calculated by the doubleyield surface model are larger than that calculated by Duncan e-b model.

Abstract:In the experiment, sea mud, mountain soil, 10%, 15%, 20% of sea mud mixed with cement (pile) soil were used as embankment filling materials. In this paper, the most suitable material for embankment filling material was studied from the aspect of consolidation characteristics. The basic physical and mechanical parameters, compression coefficient and consolidation coefficient of the sample were obtained through the basic physical and mechanical property test and standard consolidation test. Then the sample was analyzed from the angle of consolidation compression deformation and consolidation rate. The results show that:(1) the compression deformation of natural sea mud is the largest, and the consolidation rate is the smallest. (2) The compression deformation of natural mountain soil is the smallest, but the consolidation rate is lower than that of cement (pile) soil mixed with sea mud. (3) With the increase of cement content, the compression deformation of cement (pile) soil mixed with sea mud is the smallest, and the consolidation rate is the smallest compared with that of sea mud and mountain soil, but the cement content has the least effect on cement mixed with sea mud The consolidation rate of soil (pile) has little effect. Therefore, from the perspective of consolidation characteristics, it is concluded that the cement (pile) soil mixed with 20% cement is the most suitable material for embankment filling.

Abstract:Based on the field investigation of a large number of cases of seepage control and reinforcement of dangerous reservoir dams, combined with the introduction of literature, this paper sums up many factors that may affect the seepage control effect of the seepage control wall in the stage of survey, design and construction, and reasonably classifies the possible adverse effects. Based on the above classification, a simplified physical model was established, and seep/W module in GeoStudio was used to carry out seepage simulation, so as to evaluate the seepage control effect after the anti-seepage wall of earth rock dam was strengthened. Finally, taking the effect of seepage control and reinforcement of a reservoir as an example, the paper analyzed the existing quality defects, the difference of seepage control structure form, unstable seepage caused by water level change and other working conditions, evaluated the influence degree of each working condition factor on seepage control effect through the hydraulic gradient at the escape point, seepage flow and other factors, and carried out the preliminary judgment of the adverse causes of seepage control effect of seepage control body combining with the shape of seepage line, and does not The numerical simulation was carried out under the same reservoir water level and reservoir water level fluctuation conditions, and the difference of the phreatic line shape was compared and analyzed. The results show that the penetration defects seriously weaken the seepage control effect of the anti-seepage wall. Compared with the steady-state reservoir water level, the change of phreatic line under the different rate of sudden rise and fall of reservoir water level shows the phenomenon of "delayed rise"and "delayed fall" in the upstream. Through the above research, the seepage control of the dangerous reservoir is realized It can provide reference for reinforcement and renovation.

Abstract:Deep well mining brings a series of new problems to the design of the pipeline stinger beam of the shaft drainage system, such as the large load on the pipeline beams, the difficulty of type selection and the difficulty of installation. Taking a deep well auxiliary shaft as an example, measures were taken to cancel the temperature force load, and load sharing effect of U-shaped pipe clamp on the escrow beam was studied by combining the theory with practice. Through PROE software, the finite element analysis of the escrow beam was carried out with ANSYS, and the strengthening measures of the beam were creatively integrated into the selection process. The mechanical analysis of the pipeline beam of the deep well drainage system was carried out from three aspects. On the basis of ensuring the safety of the system, the effect of reducing the load of the pipeline beam was achieved, and the specification of the tube pipeline was also reduced.

Abstract:In order to understand the influence mechanism of low temperature on the strength of cemented backfill, a large-scale cemented backfill model was modeled and analyzed by using b4cast finite element software based on maturity theory. The time-varying law of temperature field and strength of the cemented backfill in low-temperature backfilling environment were obtained. In addition, the curing mechanism of cemented backfill at low temperature was revealed by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that at the initial filling temperature of 5℃, the temperature and strength of the cemented backfill increase gradually from the center of the filling body to the surrounding rock. The temperature inside the large-volume cemented backfill rises very slowly, and the central temperature only reaches 12.5℃ after 28 days. Through XRD and SEM analysis, it is found that the main hydrates in cemented backfill are ettringite and C-S-H gel. The formation rate of ettringite in low temperature determines the development of early strength of cemented backfill.

Abstract:In order to discuss sedimentary facies and sedimentary evolution of middle and upper Jurassic in the western section of South Qilian Basin. Lithological characteristics, paleontological characteristics and lithologic assemblage of middle and upper Jurassic in the study area were analyzed. The results show that the middle and upper Jurassic in the study area were composed of river diffuse, embankment, river bed deposition, fan delta plain, delta front and coastal shallow lake subfacies. Sedimentary facies studies show that Xingou-Xiangyang coal mine and Wausdosoka were belong to different sedimentary basins in Jurassic, respectively. And the differences of sediment facies are obvious, showing different processes of sediment evolution. In the middle Jurassic, the Xiangyang coal mine was mainly composed of meandering river deposit, the Xingou coal mine was mainly composed of fan delta plain deposit, and the area of Waustusoka was composed of shallow lake deposit. Late Jurassic, there were not deposit in Xiangyang coal mine, and the Xingou coal mine was mainly composed of the coastal shallow lake deposition, and the Wausdosoka area was composed of lakeside deposition.

Abstract:Based on Sentinel-2A remote sensing image data, this paper took Taihang Mountain Area as the research object to quantitatively analyze the different performance of five classification methods of maximum likelihood (ML), Bayes, support vector machine (SVM), decision tree, and random forest (RF) in the region under different feature combination modes, which adopting two strategies of pixel based and object-oriented classification. The results show that (1) the RF classifier based on pixel achieves the highest accuracy, while the overall accuracy of only using spectral features and using spectral, red edge and exponential features is 96.85% and 96.64%, respectively.(2) The addition of red edges and exponential features can have different degrees of impact on the classification accuracy of each classifier. Even if the overall accuracy of the pixel-based RF and object-oriented CART decision trees decreases, but the decline is about 0.5%. The accuracy of other classifiers has been improved.

Abstract:Taking the high-tech industries and high energy-consuming industries as examples, green innovation efficiency of high-tech industries and energy-intensive industries in Beijing-Tianjin-Hebei region from 2009 to 2016 was measured by using super efficiency SBM model that considered undesired output. On this basis, the least square regression model was used to study the relationship between green innovation efficiency and environmental regulation in Beijing-Tianjin-Hebei region. The results show that the green innovation efficiency of Beijing and Tianjin is much higher than that of other cities in Hebei province. And the green innovation efficiency of high energy-consuming industries in Hebei province is higher than that of high-tech industries. Besides, the green innovation efficiency of high-tech industries is negatively correlated with environmental regulation, negatively correlated with openness, and positively correlated with enterprise scale and r&d intensity. The green innovation efficiency of high energy-consuming industries are positively correlated with environmental regulation, negatively correlated with openness, and positively correlated with enterprise size and r&d intensity.