在暴雨作用下,大型城市极易发生内涝。基于内涝易发性和脆弱性两方面,选取年均降雨量、坡度、高程及人口密度等12项评价指标,将模糊层次分析法(Analytic Hierarchy Process,AHP)与逼近理想解排序法(Technique for Order Preference by S...在暴雨作用下,大型城市极易发生内涝。基于内涝易发性和脆弱性两方面,选取年均降雨量、坡度、高程及人口密度等12项评价指标,将模糊层次分析法(Analytic Hierarchy Process,AHP)与逼近理想解排序法(Technique for Order Preference by Similarity to the Ideal Solution,TOPSIS)进行组合,构建了城市内涝风险评估体系。以长沙市核心城区为例,进行了内涝风险评价,并利用历史内涝点数据进行了验证。内涝易发性评价结果显示,研究区内高和中内涝易发性区域分别占总面积的12.63%和29.52%,主要位于城市中部和东南部,其中芙蓉区有45.50%的区域内涝易发性高,内涝问题最为突出。此外,研究发现195个历史内涝点分别有36.41%位于高内涝易发区,45.13%位于中内涝易发区。暴雨降雨量、高程和坡度是内涝发生的最重要的3个影响因子。在考虑建筑密度、敏感性基础设施与人口密度等脆弱性指标后,研究区内涝高风险区域占总面积的12.2%,主要位于雨花区及岳麓区等人口和建筑密度较大的老城区。内涝风险评估是提升城市韧性的重要内容之一,研究可为城市内涝防灾减灾以及韧性城市的建设提供决策参考。展开更多
Triaxial cyclic loading tests have been performed to assess the influence of plastic deformation on inelastic deformational properties of anisotropic argillite with bedding planes which is regarded as a kind of transv...Triaxial cyclic loading tests have been performed to assess the influence of plastic deformation on inelastic deformational properties of anisotropic argillite with bedding planes which is regarded as a kind of transversely isotropic media.Considering argillite's anisotropy and inelastic deformational properties,theoretical formulae for calculating oriented elastic parameters were deduced by the unloading curves,which can be better fitted for the description of its elasticity than loading curves.Test results indicate that with the growth of accumulated plastic,strain,the apparent elastic modulus of argillite decreases in a form of exponential decay function,whereas the apparent Poisson ratio increase in a form of power equation.A ratio of unloading recoverable strain to the total strain increment occurred during a loading cycle is defined to illustrate the characteristic relations between anisotropic coupled elasto-plastic deformation and plastic strain.It is significant to observe that high stress level and plastic history have an inhibiting effect on argillite anisotropy.展开更多
为确定聚甲醛(POM)纤维长度和掺量对机场道面混凝土力学性能的影响机制,利用L_(9)(3^(3))正交表设计了9组正交试验组,主要研究3种不同水胶比、3种POM纤维长度、3种POM纤维掺量对机场道面混凝土抗压及抗弯拉强度影响的显著性。基于正交...为确定聚甲醛(POM)纤维长度和掺量对机场道面混凝土力学性能的影响机制,利用L_(9)(3^(3))正交表设计了9组正交试验组,主要研究3种不同水胶比、3种POM纤维长度、3种POM纤维掺量对机场道面混凝土抗压及抗弯拉强度影响的显著性。基于正交试验强度敏感性分析结果,进一步分析了POM纤维长度和掺量对机场道面混凝土力学性能的影响。结果表明:基准组试件在荷载到达限度后迅速降低,表现出脆性损坏特点,而POM纤维增强组试件的裂纹扩展较慢,表现出一定的延性损坏特点,POM纤维能够有效抑制混凝土裂纹的扩展,改善混凝土脆性,起到增韧的作用;与基准组相比,纤维增强组抗压强度和抗弯拉强度分别在0.6%~10.1%和15%范围内波动,纤维长度和掺量的改变并不能引起混凝土抗压和抗弯拉强度发生显著变化;POM纤维长度和掺量对机场道面混凝土主要控制指标28 d抗弯拉强度的影响远小于水胶比,纤维掺量对力学性能的影响小于纤维长度,且难以通过邓肯氏检验确定3个因素的最优水平;POM纤维对机场道面混凝土残余抗弯拉强度(韧性)有显著提升,12 mm POM纤维在1.2%混凝土体积掺量时对韧性提升效果最优,并据此认为其对机场道面混凝土28 d抗弯拉性能改善效果最好。展开更多
Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress ...Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.展开更多
文摘在暴雨作用下,大型城市极易发生内涝。基于内涝易发性和脆弱性两方面,选取年均降雨量、坡度、高程及人口密度等12项评价指标,将模糊层次分析法(Analytic Hierarchy Process,AHP)与逼近理想解排序法(Technique for Order Preference by Similarity to the Ideal Solution,TOPSIS)进行组合,构建了城市内涝风险评估体系。以长沙市核心城区为例,进行了内涝风险评价,并利用历史内涝点数据进行了验证。内涝易发性评价结果显示,研究区内高和中内涝易发性区域分别占总面积的12.63%和29.52%,主要位于城市中部和东南部,其中芙蓉区有45.50%的区域内涝易发性高,内涝问题最为突出。此外,研究发现195个历史内涝点分别有36.41%位于高内涝易发区,45.13%位于中内涝易发区。暴雨降雨量、高程和坡度是内涝发生的最重要的3个影响因子。在考虑建筑密度、敏感性基础设施与人口密度等脆弱性指标后,研究区内涝高风险区域占总面积的12.2%,主要位于雨花区及岳麓区等人口和建筑密度较大的老城区。内涝风险评估是提升城市韧性的重要内容之一,研究可为城市内涝防灾减灾以及韧性城市的建设提供决策参考。
基金Program(2011CB710601) supported by National Basic Research Program of ChinaProject(50925933) supported by National Natural Science Foundation of China+1 种基金Project(2008BAB29B03) supported by National Key Technology Research and Development Program of ChinaProject(2010-122-011) supported by Guizhou Provincial Department of Transportation,China
文摘Triaxial cyclic loading tests have been performed to assess the influence of plastic deformation on inelastic deformational properties of anisotropic argillite with bedding planes which is regarded as a kind of transversely isotropic media.Considering argillite's anisotropy and inelastic deformational properties,theoretical formulae for calculating oriented elastic parameters were deduced by the unloading curves,which can be better fitted for the description of its elasticity than loading curves.Test results indicate that with the growth of accumulated plastic,strain,the apparent elastic modulus of argillite decreases in a form of exponential decay function,whereas the apparent Poisson ratio increase in a form of power equation.A ratio of unloading recoverable strain to the total strain increment occurred during a loading cycle is defined to illustrate the characteristic relations between anisotropic coupled elasto-plastic deformation and plastic strain.It is significant to observe that high stress level and plastic history have an inhibiting effect on argillite anisotropy.
文摘为确定聚甲醛(POM)纤维长度和掺量对机场道面混凝土力学性能的影响机制,利用L_(9)(3^(3))正交表设计了9组正交试验组,主要研究3种不同水胶比、3种POM纤维长度、3种POM纤维掺量对机场道面混凝土抗压及抗弯拉强度影响的显著性。基于正交试验强度敏感性分析结果,进一步分析了POM纤维长度和掺量对机场道面混凝土力学性能的影响。结果表明:基准组试件在荷载到达限度后迅速降低,表现出脆性损坏特点,而POM纤维增强组试件的裂纹扩展较慢,表现出一定的延性损坏特点,POM纤维能够有效抑制混凝土裂纹的扩展,改善混凝土脆性,起到增韧的作用;与基准组相比,纤维增强组抗压强度和抗弯拉强度分别在0.6%~10.1%和15%范围内波动,纤维长度和掺量的改变并不能引起混凝土抗压和抗弯拉强度发生显著变化;POM纤维长度和掺量对机场道面混凝土主要控制指标28 d抗弯拉强度的影响远小于水胶比,纤维掺量对力学性能的影响小于纤维长度,且难以通过邓肯氏检验确定3个因素的最优水平;POM纤维对机场道面混凝土残余抗弯拉强度(韧性)有显著提升,12 mm POM纤维在1.2%混凝土体积掺量时对韧性提升效果最优,并据此认为其对机场道面混凝土28 d抗弯拉性能改善效果最好。
基金Projects(11172090,51009052,51109069) supported by the National Natural Science Foundation of ChinaProject(2011CB013504) supported by the National Basic Research Program of China
文摘Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.
