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•The mechanical performances of U-steel support and CFST support were compared.•The special-shaped CFST support was put forward.•The bearing capacity of the special-shaped and ...circular CFST supports were compared.
The concrete-filled steel tubular (CFST) support has been proposed as a new passive support form for controlling the stability of surrounding rock in deep roadway. To explore the mechanism of CFST support in deep roadway, the mechanical performances of U-steel support and CFST support were compared by theoretical calculation and numerical simulation with the engineering background of 11031 ventilation roadway in Pingmei coal mine. Then, the section shape of CFST was optimized and the special-shaped CFST support was put forward. The special-shaped CFST support was applied to 11031 ventilation roadway of U36-steel support failed to control. The results indicate that: The ultimate bearing capacity of CFST support is much greater than that of U-steel support. The CFST support can provide great supporting force to the roof-floor and two sides of roadway. It can be applied to the roadway with large horizontal stress. The section bending modulus and ultimate bearing capacity of the special-shaped CFST support are greater than those of the circular CFST support. The displacements of 11031 ventilation roadway supported by the special-shaped CFST support was not great. So, the special-shaped CFST support can effectively control the surrounding rock in 11303 ventilation roadway.
•Random Forest models show total nitrogen and phosphate are the primary predictors of the lake-wide phytoplankton biomass.•Phytoplankton biomass with its predictor and response relationships show ...spatial heterogeneity at the local scale.•Chlorophyll a was negatively correlated with total phosphorus and phosphate in Lake Okeechobee.
The over-proliferation of phytoplankton has been a public concern for the last several decades. To evaluate the importance of different environmental factors on phytoplankton biomass variations with their complex response relationships in the large eutrophic Lake Okeechobee, the nonlinear methods including Generalized Additive Model (GAM) and Random Forest (RF) algorithm were employed. A long-term monitoring dataset of 8 sampling sites ranging from January 1996 to December 2010 was applied to explore the driven factors and response relationships of phytoplankton biomass from the different scales in Lake Okeechobee. Results showed a spatially heterogeneous distribution of phytoplankton biomass there, and the western and southern littoral zones occurred heavier algal blooms than the central pelagic zones. Spearman’s correlation results denoted Chlorophyll a (Chla) was negatively correlated with phosphorus in different scales. In the aspect of temporal variations, phytoplankton biomass appeared a three-peak-two-valley variation trend there, which peaked in 1997, 2003, and 2010, respectively. On the lake-wide scale, the RF model indicated that the inorganic nutrients were the primary predictors of phytoplankton biomass, while underwater light availability factors were followed to play essential roles in the prediction. On the local scale, total nitrogen (TN) was the top predictor in the western near-shore zone, while other zones were nitrate and nitrite (NO23) or phosphate (PO4). GAM results suggested that phytoplankton biomass had positive response to TN increase in both lake-wide and local scales. However, its response to water temperature (WT) appeared spatial heterogeneity. This study provided a new perspective to evaluate the primary predictors of phytoplankton biomass with their response relationships from lake-wide scale and local scale in the large shallow eutrophic lake, and the importance of taking spatial heterogeneity into account for lake water quality management was stressed.
With cement, bentonite, water glass, J85 accelerator, retarder and water as raw materials, a new composite grouting material used to seal groundwater inflow and reinforce wall rock in deep fractured ...rock mass was developed in this paper. Based on the reaction mechanism of raw material, the pumpable time, stone rate, initial setting time, plastic strength and unconfined compressive strength of multi-group proportion grouts were tested by orthogonal experiment. Then, the optimum proportion of composite grouting material was selected and applied to the grouting engineering for sealing groundwater inflow and reinforcing wall rock in mine shaft lining. The results show the mixing proportion of the maximum pumpable time, maximum stone rate and minimum initial setting time of grout are A
B
C
D
, A
B
C
D
and A
B
C
D
, respectively. The mixing proportion of the maximum plastic strength and unconfined compressive strength of grouts concretion bodies are A
B
C
D
and A
B
C
D
, respectively. Balanced the above 5 indicators overall and determined the optimum proportion of grouts: bentonite-cement ratio of 1.0, water-solid ratio of 3.5, accelerator content of 2.9% and retarder content of 1.45%. This new composite grouting material had good effect on the grouting engineering for sealing groundwater inflow and reinforcing wall rock in deep fractured rock mass.
•An new self-stress grouting reinforcement method for fractured rock mass was proposed.•The reinforcement mechanism of the self-stress grouting for fractured rock mass were investigated by ...theoretical analysis.•The reinforcement effects of self-stress grouting and ordinary grouting on fractured sandstones were compared through physical experiments.•The self-stress grouting reinforcement method was used to control the surrounding rock of the substation roadway of Pingmei No.10 Mine.
Grouting has been proposed as a effective reinforcement method for the fractured rock of underground engineering. However, ordinary cement-based grouting materials have self-shrinkage due to hydration reaction, resulting in the grouting reinforcement effect of the fractured rock mass being greatly reduced. The paper proposed the new self-stress grouting reinforcement method for fractured rock mass. Its advantages include increasing the compactness of the slurry stone and improving the stress of grouting reinforced rock mass. Based on the self-stress grouting reinforcement model of fractured rock mass, the mechanism and effect of self-stress grouting for reinforcing fractured rock mass were investigated by theoretical analysis, physical experiments, and field experiments with the engineering background of the substation roadway of Pingmei No.10 Mine. The results showed that the compressive stress at the slurry-rock interface was increased due to the swelling stress of the self-stress slurry stone. So, the ultimate shear strength of the slurry-rock interface was improved. The larger the swelling stress of the slurry stone, the more obvious the reinforcement effect on the fractured rock mass. As the distance from the slurry stone increases, the effect of self-stress on the rock mass gradually decreases. The peak strength and elastic modulus of the self-stress grouting reinforced sandstone were 1.11 and 1.043 times those of the ordinary grouting reinforced sandstone. The surrounding rock of the the substation roadway with the multiple support methods failed to control was effectively controlled by the self-stress grouting reinforcement method.
•A new prestressed yield bolt was proposed with the engineering background of Shangping roadway in Huafeng Coal Mine.•The reasons for the failure of the surrounding rock control of Shangping roadway ...were analyzed.•The structure and characteristics of the prestressed yield bolt were investigated.•The yielding support scheme was applied to Shangping roadway.
The elastic elongation of the bolt itself is insufficient to meet the surrounding rock deformation in deep high-stress roadway, resulting in a large number of breakage of the bolt and the instability of the surrounding rock. Aiming at this problem, this paper proposed a new prestressed yield bolt with the engineering background of Shangping roadway in Huafeng Coal Mine. Based on the analysis of instability of Shangping roadway surrounding rock, the structure, characteristics and mechanical properties of the prestressed yield bolt was investigated. The yielding properties and deformation process of different yielding members were researched in detail. According to the engineering background, the yielding support scheme were designed and applied. The results showed that the yielding effect of yielding pipe was more obvious than that of the wooden pallet. The yielding load, the maximum yielding deformation, the yield stability coefficient of the designed yielding pipe were 190 kN, 25 mm, 1.6 kN/mm, respectively. The stability forces of the bolts in the roof, the top corner of the right side and the bottom corner of the left side of the roadway were almost the same. The overall deformation of the roadway controlled by the yielding support scheme was not large. So, the yielding pipe protected the bolt-rod from being damaged due to excessive deformation, thereby realizing the yield bolt to control the stability of the roadway surrounding rock for a long time.
Grouting has been proposed as an effective reinforcement method for fractured rock. The paper proposed a new prestressed anchor-grouting reinforcement method for underground broken rock with ...engineering background of anchor net failed to control the track haulage roadway of Daxing Mine. It combines prestressed anchor and self-stressing grouting reinforced material for broken rock. The self-stressing grouting material was first proposed by us. The paper investigated the mechanism and method of the new prestressed anchor-grouting reinforcement. The effect of the new prestressed anchor-grouting reinforcement was verified by numerical simulation and engineering application. The results showed that the new prestressed anchor-grouting reinforcement could restore the loose surrounding rock to the approximately three-dimensional stress state. It had higher strength and better effect than the anchor net. The new self-stressing grouting materials developed included Superfine Portland Cement of 92%, expansion agent content of 8%, early strength agent content of 2%, water reducer content of 1.5%. The deformations of the surrounding rock controlled by the prestressed anchor-grouting were obviously smaller than those controlled by anchor net, indicating that the prestressed anchor-grouting support had a significant effect on controlling the roadway surrounding rock.
The aim of this study was to investigate the properties of fiber-reinforced pervious concrete. Ordinary cement, silica fume, coarse aggregate, and basalt fibers were used to produce the concrete mix. ...The fibers were mixed with pervious concrete at the levels of 0 kg/m3, 2 kg/m3, 4 kg/m3, 6 kg/m3, and 8 kg/m3 to the investigate their influence on the mechanical and physical properties of pervious concrete. It could be observed that the cubic compressive strength, axial compressive strength, and flexural strength increased and then decreased as the content of basalt fiber increased, while the permeability and porosity of the pervious concrete decreased with the increase in the basalt fiber content. The mesostructure of pervious concrete was also studied through industrial computed tomography (ICT); the testing phenomenon showed that the fibers had a significant influence on the arrangement of the aggregate, cement paste, and the interfacial transition zone, and excessive basalt fiber resulted in poor characteristics of the interfacial transition zone (ITZ) and inferior strength properties. It was found that incorporating a basalt fiber content of 4 kg/m3 could achieve a balance between the mechanical and physical properties of pervious concrete, which was suitable for structural applications.
The aim of this study was to develop an efficient and accurate platform for the detection of the newly identified goose megrivirus (GoMV). To achieve this goal, we developed a TaqMan real-time PCR ...technology for the rapid detection and identification of GoMV. Our data showed that the established TaqMan real-time PCR assay had high sensitivity, with the lowest detection limit of 67.3 copies/μL. No positive signal can be observed from other goose origin viruses (including AIV, GPV, GoCV, GHPyV, and GoAstV), with strong specificity. The coefficients of variation of repeated intragroup and intergroup tests were all less than 1.5%, with excellent repeatability. Clinical sample investigation data from domestic Minbei White geese firstly provided evidence that GoMV can be transmitted both horizontally and vertically. In conclusion, since the TaqMan real-time PCR method has high sensitivity, specificity, and reproducibility, it can be a useful candidate tool for GoMV epidemiological investigation.
•Combined effects of earth-tube and building thermal mass are investigated.•Both annual and daily fluctuations of indoor air temperature are considered.•Time lag is greater than 6h in a day and can ...be tens of days in a year.•Indoor thermal comfort can be achieved by the combined system.•The proposed explicit formulas can be used for design and evaluation.
Both earth-tube systems and building thermal mass have the potential to provide desired performance levels for both indoor thermal comfort and energy saving; however, their coupling effects need to be further investigated. A model for evaluation of the combined effects of earth-tube ventilation systems and building thermal mass is proposed. Both the time-averaged indoor air temperatures and periodic temperature fluctuations are given as explicit formulas. Unlike the time lag induced by the separate use of building thermal mass, which is no longer than 6h, the combination with an earth-tube system could extend the time lag of indoor air temperature in an annual fluctuation period by tens of days and that of a daily period by a couple of hours. It is noticeable that the building thermal mass has significant impact on the effectiveness of earth-tube systems; therefore, a small heat transfer coefficient of external envelopes helps increase the annual time lag of indoor air temperature. Using a proper combination of building thermal mass and earth tubes, indoor thermal comfort can be achieved for a building located in a region with both hot summers and cold winters without any additional cooling or heating load.
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