Abstract:During the tunnel construction in the karst area, there is a great danger of water inrush, and the discharge of groundwater will lead to the geological disasters. The hydrogeology in Zhongliang mountain tunnel area was analyzed and the BP neural network optimized by the genetic algorithm is used for inverse analysis of the permeability coefficient of aquifer. The impact of tunnel elevation and the discharge of groundwater on groundwater environment change was studied, and the groundwater environment change with time was explored. The results show that water inrush during karst tunnels construction is most likely to occur on the interface between the aquifuge and the aquifer, and that tunnel elevation and the discharge of groundwater have both great impacts on the groundwater environment. The results indicate that the groundwater level drops rapidly and cannot return to the original level in the current drainage conditions. Consequently the discharge of groundwater should be controlled properly during construction. Measures should be also taken to protect the groundwater environment during construction and operation stage of tunnels.

Abstract:Glass Fiber Reinforced Polymer (GFRP) was widely used in civil engineering considering its advantages of lightweight, high tensile strength, corrosion resistance and fatigue resistance, etc. GFRP composite pile is a new type of pile reinforced by GFRP upon RC pile to enhance its bending resistance. The lateral displacement and bending moment of the RC pile and GFRP composite pile were obtained and analyzed via the model test. The lateral bearing capacity of both two pile types were compared and analyzed. The GFRP composite pile under lateral loadings was simulated by the FEA software ABAQUS. The experimental results are in good agreement with the numerical simulation results, both shouing that the bending moment distribution of GFRP composite pile was consistent with the RC pile, and the maximum bending moment occurred nearby the depth of 1/4 to 1/3 pile length. However, the horizontal load-bearing capacity of GFRP composite pile was much greater. The elastic modulus and lateral ultimate capacity of GFRP composite pile covered with a layer of GFRP unidirectional fabric canbe improved to a certain extent.

Abstract:Tunnel safety has long been a major concern for transportation and government entities. Noxious fumes, deadly gasses, groundwater seepage and flooding threats have occurred in main transportation systems. It is necessary to isolate the water inrush area as soon as possible, to gain time for further treatment. The method of stopping water using large-diameter airbags is quite efficient, and the contact area between the surface of the airbag and the tunnel inner wall will produce frictional force to resist the fluid pressure from expansion of wetting area. This paper assumes that the airbag can't be stretched, and combining with the boundary conditions in the tunnel of the airbag and the stress condition, the deformation and the force characteristics of the airbag under external pressure are studied. Formula of shape change and internal pressure increase of the airbag is obtained, and the relationship between the external and internal pressure is proposed. The control factors for leakage resistance, influence of the aspect ratio, as well as initial pressure on the shape and internal pressure were analyzed. The theoretical formula is verified via the model test, indicating good agreement.

Abstract:To simulate the influence of non-continuous rainfall on the friction of pile foundation in Lanzhou collapsible loess, field test was carried out via natural infiltration method. The project measures the pile side friction by embedding the steel bar and the immersion depth by water probe. The results show that the maximum water immersion is about 10 meters, and the increase of water content below this depth is marginal. During the test, the negative friction resistance is taking effect, and its peak increases when the load increases. At the loading stage, the length of the negative friction resistance is about 0.24 times the pile length, subjected to certain fluctuation. During the unloading process, there is still negative friction resistance, and the interval length fluctuates within the range of 0.28~0.45 times the pile length. The results show that the initial rainfall has a significant influence on the pile foundation, and the effect of continuous intermittent rainfall is marginal. The actual negative friction resistance is much smaller than the threshold. Consequently for pile design, it is necessary to fully consider the impact of the initial rainfall.The pice length should also be adjusted based on the negative friction resistance.

Abstract:The relationship between pile numbers and settlement is the most important reference for pile foundation design, based on the deformation control (or design of reducing settlement pile foundation), which is affected by several factors, such as the loading magnitude,the pile arrangement and the soil type. Combined with the measured data from case history, the approximate numerical method and plane strain finite element method are put forward to analyze two piled raft foundations with different pile numbers for multi-storey residential buildings. The effects of different pile spacings on compressive deformation, internal force of foundation and stress-strain distribution of soils are studied, and a reasonable explanation is given for the problem that foundation settlement is almost unchanged after the pile number is reduced by half. The results show that, the lower the loading magnitude or the smaller the compressibility difference between pile side and pile tip soil layer, the foundation settlement is less sensitive to the change of pile numbers. For low-cap pile group foundation in deep soft soil, pile foundation design based on deformation control can reduce pile numbers considerably, with significant economic benefits.

Abstract:The steel reinforced concrete shear wall is widely used in high-rise buildings for its high strength, high stiffness and excellent stability. In order to study the influence of different steel types on its anti-seismic performance, low cyclic loading test has been carried out, including three experiments on the 1/3 scale of steel reinforced concrete shear walls (the steel as brace is X-type, AC1-type and AC2-type, respectively) and one contrast experiment on a standard reinforced concrete shear wall. According to the failure process and modes, the bearing capacity, crack propagation, stiffness, ductility and energy dissipation of shear wall were significantly influenced. The experimental results show that the steel bracings results in a better performance of the bearing capacity, stiffness, ductility and energy dissipation capacity of the shear wall. The ultimate bearing capacity of shear wall was increased by 71.9%, 64.6% and 49.4% using AC1-type, AC2-type and X-type, respectively. The ductility coefficient was increased by 19.3%, 5.0% and 14.5% accordingly. The stiffness of the steel reinforced concrete shear wall with steel bracings is much better than that of the contrast specimen and the stiffness degradation rate is slower in the middle and later stages of experiment. In addition, the plastic zone of the steel reinforced concrete shear wall with steel bracings increases dramatically, and the hysteretic loop is more full.

Abstract:The variation of the environmental factors of marine soft soil in industry zones of Qinzhou Port and Fangcheng Port was analyzed. The soil soaking load linkage is a self-developed device for mechanism simulation, used to examine the environmental factors of marine soft soil when the thickness of coastal reclamation layer and concentration of chemical constituents of pore water ions changed. The soft soil samples were obtained artificially. Direct shear tests of threse artificial soft soil samples were carried out. The test results showed that cohesive force c and internal friction angle φ of artificial soft soil samples changed with calcium ion larger than magnesium ion when concentration of calcium ion or magnesium ion increased. There is certain coupling effect between the additional load stress of coastal reclamation layer and ion concentration of soak liquid for the shear strength indexes of the soil. However, the coupling effect of cohesive force is obvious while that of internal friction angle is less significant.

Abstract:Considering soil arching effects, the internal friction angle and cohesive force between pile and soil, between soil particles are generally under nonlimit state. Cohesive soil slope supported by flexible pile is studied and the potential slope sliding surface is searched and the formulas of the active earth pressure of cohesive soil under nonlimit state against flexible pile is derived via Mohr circle of stress, micro layer analysis method as well as the static equilibrium. The difference between the theory proposed and Rankine solution is studied via comparison with engineering applications. The active earth pressure calculated by proposed method in this paper is greater, while the location impacted by resultant force of the active earth pressure is higher. Besides, the ranse of potential sliding surface is smaller than that of sliding surface under Rankine limit state.

Abstract:The existence of defects significantly affects the quality of underground engineering, making it necessary to detect the existence of defects with geophysical methods. The fluctuation characteristics of Rayleigh wave in the medium containing defects were analyzed with the finite element method, and quantitative analytical methods of shape parameters and position of defects were proposed. The horizontal position of defects is defined based on the propagation time difference between the incident Rayleigh wave and the reflected Rayleigh wave, while the depth of defects is obtained with the critical disturbance frequency method.The size of defects is determined with the energy attenuation rate method. The results show that the energy of Rayleigh wave attenuates and reflects during the process of propagation along the surface of the medium. It can be observed that results from the proposed method are in good agreement with the measured data.

Abstract:Based on the laboratory full-scale tensile failure tests on four full-bonded GFRP anti-anchors socketed into rock, the interfacial adhesion and bearing capacity of the anchor on rock foundation were studied, from which the micro-failure mechanism of the anchor was revealed. The results show that the pull-out failure occurred in GFRP anti-floating anchor, attributing to the dilative shear failure from anchor thread's interfacial deterioration. The ultimate uplift bearing capacity of GFRP anti-floating anchor with diameter of 25 mm, concrete of M30, anchorage length of 1.3 m and 0.55 m, was 255 kN and 195 kN, respectively, indicating that the high bearing capacity of the anchor for anti-floating purpose. The average bond strength between GFRP anti-floating anchor and grouting body was between 2.41 MPa and 5.10 MPa, higher than the recommended values from Technical Code for Engineering of Ground Anchoring and Shotcrete Support"(GB 50086-2015).

Abstract:As the major flaw of highway tunnels, lining cracks of highway tunnels is increasingly seriously. In order to study the mechanism of crack propagation in highway tunnels under loading, this article conducts numerical simulation on the crack propagation with discrete element software PFC, demonstrating the disaster mechanism of crack propagation in highway tunnels,and establishing the corresponding prediction models. The results showed that:integral safety of lining is subject to pre-existing flaws, and the positions of pre-existing flaws are generally relatively more dangerous in lining; the depth of pre-existing flaws plays an important role in the timing of crack coalescence,i.e.,the deeper the pre-exsiting flaws are, the less time is needed to achieve crack coalescence in the lining; the depth of pre-exsiting flaws has a great influence on the variation of crack opening, i.e. the deeper pre-exsiting flaws are, the increasing opening those fracture apertures will be, and there is an obvious abrupt change when the flaws coalesce.

Abstract:The groundwater level rises once the drainage hole of high slope is blocked during construction or operation, affecting the slope stability and safety of the supporting structure. Based on the law of seepage refraction, this paper focuses on the changes of groundwater level and the mechanical response of supporting structure in cases of different blockage conditions. The calculation results firstly demonstrate that the impact of the drainage hole blockage on pore water pressure development is significant, and that the displacement change within the slope is less obvious. Secondly the axial force along the anchor rod of the slope increases obviously with the maximum growth rate of 45%. In addition, for the high slope in the rock formation arranged with the deep drainage hole, the displacement and stress of the support structure changes significantly after the drainage hole blockage. Therefore, the impact on the supporting structure should not be ignored, especially in the position of the shear outlet on the slope toe. Safety factor of the slope decreases significantly when the drainage hole is almost completely clogged. This paper also introduces a high slope treatment method of the supporting system adopting the frame type and anchor rod, that is, for the lower part of the slope, strengthening the lattice support strength; and for the upper part of the slope, increasing the anchorage length of the anchor rod.

Abstract:Based on the ultimate load test of the national power grid of 500kV transmission line project from Luping to Fule, this paper carried out the ultimate load test of 3 rock-socketed piles with enlarged base. The load-displacement curves, distribution of axial force of pile shaft and shaft resistance were investigated. Results show that, when the piles located in the same layer of rock-soil and the length are reached, the enlarge base pile can not only increase the ultimate uplift bearing capacity, but also reduce the displacement of pile top than the pile of uniform section. The properties of the rock mass of the enlarged head have great influence on the uplift force. For the rock socketed uplift pile with enlarged bottom, the uplift force of the enlarged head is higher than that of the ultimate uplift load of the pile, and the expansion action of the enlarged head is more significant. The uplift pile of a clay layer with a certain thickness and a strong weathered layer in a medium weathered layer with enlarged head and a uniform section at the upper end of the enlarged head, the limit side friction of the section with the clay layer and the strong weathered rock layer can be improved appropriately according to the actual situation of the project on the basis of the recommended by the building codes.

Abstract:For the stability analysis of cohesive soil slope with weak interlayer under condition of heavy rainfall, a new method is proposed based on the slope investigation data and the fleory of unsaturated seepage and shear strength to analysis the seepage characteristics and variation of safety coefficient for soil slopes containing weak interlayers. Analysis results indicate:due to rainfall infiltration, the transient saturated zone is formed in the weak interlayer of slope; Under rainfall infiltration process, there is positive correlation between the suction and the vertical effective stress; With increase of rainfall duration, the plastic zone extended from the inside interlayer to the top of slope, as a result of which the slope safety coefficient decreases; After rain, weak interlayer will still exist in local transient saturated zone, causing less significant decrease of the slope safety coefficient. According to the numerical results, the instability process of cohesive soil slopes can be divided into 5 stages:interlayer softening,interlayer extrusion,tensile crack,slope crest settlement and fault slip. Consequently, to minimize the influence of heavy rainfall on the slope stability, reasonable drainage system should be emphasized in the design of cohesive soil slope with weak interlayer.

Abstract:Microcystis aeruginosa was used as the experimental subject to examine the algae-lysing characteristics of algicidal bacteria R1(Lysinibacillus macroides),which was isolated and purified from Taihu fish innards, named Surf fish. The ability of algae-lysing, the degradation products, algae-lysing mechanism and active algicidal substances were studied with the measurement of chlorophyll a and the three dimensional fluorescence technology, the whole experimental process was carried out through high temperature treatment, acid and alkali treatment, dialysis treatment and HPLC separation technique. The results show that the strain R1 can remove Microcystis aeruginosa effectively. The contents of chl-a decrease from 205.11 mg/L to 35.61 mg/L in 10 days, with degradation rate of 82.64%. The degradation rate is 89.8% measured by 3-D flurescence technology in 10 d, which is similar to the result measured by measuring Chlorophyll-a. The fluorescence spectrometric analysis shows that the tryptophan increases and the humic acid decreases significantly. The main dissolved algal products are long-wave class tryptophan, which are mainly intracellular substances.The soluble alga may be hydrophobic acid. The active algae-lysing substances produced by R1 with molecular weight less than 500 da, are identified as bacteria secretion, could resist acid and be promoted in alkaline conditions. Active substance was separated from R1 crude extract by HPLC,and a further identification was necessary to be processed.

Abstract:With experiment test, a second-order orthogonal experiment was carried out to analyze the weight of factors affecting H₂S and NH₃ concentration in sludge dewatering of underground wastewater treatment plants:temperature, humidity and exhaust volume, and according to pollution level and energy consumption, a comprehensive evaluation index was put forward. The results indicate that Interaction between temperature and exhaust volume is important to H₂S and NH₃ concentration (p<0.05). When the outdoor temperature is 20℃, the H₂S and NH₃ concentration of the dewatering machine room is the lowest. It is reduced by 2.5 times compared with 35℃. According to the comprehensive evaluation index, the minimum K value is 4.5 in the ventilation frequency of 2.7. Below 2.7 times of ventilation, the odor concentration is too high, and the energy consumption is too large when higher than the 2.7 times of ventilation. Therefore, the most appropriate number of ventilation is 2.7 for dewatering room with treatment capacity ten thousand per day.

Abstract:Based on water quality data of 4 stations in the Dawen River from 2007 to 2014, this paper analyzed the inter-annual variability of 9 indicators such as dissolved oxygen, chemical oxygen demand, ammonia nitrogen etc., and evaluated water quality by a Grey Model. By the site investigation of 9 cascade reservoirs during the rich, average and dry period in 2015, the spatiotemporal variation of nitrogen and phosphorus nutrients were analyzed, nutritional level was assessed by TLI.The results show that during the period of 2007 to 2014, the organic pollution have been effectively alleviated by the emission reduction measures in the basin, the concentrations of TP have been meliorated obviously while the concentrations of TN have been aggravated integrally by the construction of cascade reservoirs. The grey comprehensive index shows that the water quality of the Dawen River is improved and the seasonal fluctuations tend to be stable. The state of eutrophication has apparent difference among cascade reservoirs because the contamination vary in degree. Part of the reservoirs have been experienced cyanobacteria and diatom blooms during rainy and dry seasons. The different flow conditions induced by different discharge in corresponding season have great influence on water quality of the reservoirs., the difference of flow condition caused by the water pollution level, damming and impoundment have a significant impact on the growth and bloom of algae in reservoirs.

Abstract:In order to detect the toxicity of algicidal products and valuate the harm of microcystin in the water source to the human body, the luminescent bacteria was to determine the toxicity, USEPA recommended model provided a health risk assessment of source water. The results show that the strain Y1 inhibit the growth of microcystis aeruginosa effectively. The strain had a slight toxicity to the luminescent bacteria. When the concentration of chlorophyll a was 34.92 mg/m³, the increase of dosage could enhance the toxicity of algae. The toxicity of liquid algae added bacteria was significantly lower than that of the control group, when the concentration of chlorophyll a was greater than 46.56 mg/m³. The non carcinogenic risked index of MC-LR in the water source was 2.89~4.87, which was reduced to 1.3 after BAF treatment, even to 0.6 after adding strain Y1. It reached health risk assessment safety standards when the the value was less than 1. Through the prediction model, it was found that the organic matter in treated water had no mutagenicity, it indicated that waters with strain Y1 had not biotoxicity and mutagenicity.

Abstract:This study aimed at the pollution problems of organic matter, algal and nitrogen pollution in drinking water sources, the biological aerated filter (BAF) was used to treat micro polluted source water. The removal effects of NH₃-N, TN(total nitrogen), TP(total phosphorus), CODMn, Chl-a, UV₂₅₄ under the different hydraulic load were examined. The results showed that the average removal rates of NH₃-N, TN, TP, COD_Mn, Chl-a, MC-LRand UV254 were 74.71%, 46.55%, 81.8%, 52.16%, 67.99%, 79.2% and 34.8% respectively at the hydraulic loading of 0.07m³/(m²·h). The minimum effluent concentration of NH₃-N, TP, CODMn met Ⅱ class national standard of Surface Water Environmental Quality Standards(GB 3838-2002). The analysis of biological microscopy and high-throughput sequencing (454) showed that the microbial community on the biofilm of BAF was extremely rich in the micro-polluted source water of low carbon source. At the early stage (the first 2 weeks), the microflora on the biofilm had 17 major genera and 6 species. At the later stage (3 to 4 weeks later) the microflora increased to 43 major genera and 14 species. Protists such as nematodes, paramecium and daphnia, were also observed. The dominant species were Sphaerotilus (2.41%~24.58%), Aeromonas (4.16%~12.59%), Cloacibacterium(1.85%~12.39%), Aquabacterium (1.53%~6.76%), Hydrogenophaga (1.12%~5.9%), Methyloversatilis (0.53%~1.52%), Rhodobacter (0.09%~1.39%). Microbial degradation is mainly responsible for the treatment of organic matter and nitrogen pollution in drinking water sources by BAF. The physical filtration, adsorption and ion exchange of zeolite also play an important role in the treatment of organic matter and nitrogen pollution in drinking water sources. A high removal ratios for nitrogen, phosphorus and algae pollutants can be achieved in BAF. This study has certain theoretical significance and engineering application value for biological pretreatment of micro polluted source water.