In order to effectively assess the mechanical properties of concrete with freeze-thaw and seawater erosion, tests about basic mechanical properties of concrete after freeze-thaw and seawater erosion are conducted base...In order to effectively assess the mechanical properties of concrete with freeze-thaw and seawater erosion, tests about basic mechanical properties of concrete after freeze-thaw and seawater erosion are conducted based on the large-scale static and dynamic stiffness servo test set. 50, 100, 200 and 300 cycles of freeze-thaw cycling are made on normal concrete, and the artificial seawater is produced. The reasonable wet and dry accelerate system is selected. 10, 20, 30, 40, 50 and 60 cycles of wet and dry cycling are made to concrete after freeze-thaw cycling. The degeneration law of the concrete elastic modulus and compressive strength is studied. The Ottosen tri-axial strength criterion considering cycles of freeze-thaw and wet and dry cycling is deduced based on uniaxial mechanical properties of concrete and damage theory. Experimental results show that with the increase in the number of wet and dry cycles and freeze-thaw cycles, the concrete axial compressive strength and the elastic modulus decline gradually. Tensile and compressive meridians of concrete shrink gradually. The research can be referenced for anti-crack design of actual structures eroded by seawater at cold regions.展开更多
Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expan...Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expansive soils,the effectiveness and accuracy of free swelling ratio should be highly required.However,due to the deficiency of geotechnical test regulations for the free swelling ratio test,non-negligible variation difference is often observed among the test results of the same type of soil samples.Thus,a series of laboratory tests are conducted to figure out the influences of soil particle size,initial soil temperature,and wet-dry circulation on the free swelling ratio of expansive soils.The results show that the initial soil temperature exerts an obvious influence on free swelling ratio and a relative weak influence on soil mass of expansive soil with the micro soil particle size(d<0.075 mm),and the correlation becomes unclear when soil particle size is within the range of 0.075 mm≤d<0.500 mm.A larger particle size of expansive soils induces a larger free swelling ratio and soil mass in the soil measuring cup regardless of initial soil temperature.However,the enlarging amplitude decreases as the particle size of expansive soils increases.There is a progressive enlargement of free swelling ratio at the first two wet-dry cycles and then it attenuates gradually when the number of wetdry cycles further increases.展开更多
To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials(RCBMs) with dry-and wet-curing conditions, uniaxial compression and cyclic loading-unloading tests were...To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials(RCBMs) with dry-and wet-curing conditions, uniaxial compression and cyclic loading-unloading tests were carried out on rubber cement mortar(RCM). The mechanical properties of the uniaxial compression specimens cured at 95%(wet-curing) and 50%(dry-curing) relative humidities and cyclic loading-unloading specimens cured at wet-curing were analyzed. Under uniaxial compression, the peak stress loss ratio is higher for dry-curing than for wet-curing. The peak strain decreases with the increase of rubber content, and the peak strain increases with the decrease of curing humidity. Under cyclic loading-unloading, the variation trends of residual strain differences of the normal cement mortar and RCM at each cyclic level with the number of cycles are basically the same, but the failure modes are different. The analysis of the internal mesostructure by a scanning electron microscope(SEM) shows that initial damage is further enhanced by reducing curing humidity and adding rubber aggregate. The damage constitutive model based on strain equivalence principle and statistical theories was used to describe the uniaxial compression characteristics of RCM, and the law of mechanical damage evolution was predicted.展开更多
基金The Natural Science Foundation of Shandong Province(No.ZR2009FQ020)the Ph.D.Programs Foundation of Ministry of Education of China(No.20100131120042)
文摘In order to effectively assess the mechanical properties of concrete with freeze-thaw and seawater erosion, tests about basic mechanical properties of concrete after freeze-thaw and seawater erosion are conducted based on the large-scale static and dynamic stiffness servo test set. 50, 100, 200 and 300 cycles of freeze-thaw cycling are made on normal concrete, and the artificial seawater is produced. The reasonable wet and dry accelerate system is selected. 10, 20, 30, 40, 50 and 60 cycles of wet and dry cycling are made to concrete after freeze-thaw cycling. The degeneration law of the concrete elastic modulus and compressive strength is studied. The Ottosen tri-axial strength criterion considering cycles of freeze-thaw and wet and dry cycling is deduced based on uniaxial mechanical properties of concrete and damage theory. Experimental results show that with the increase in the number of wet and dry cycles and freeze-thaw cycles, the concrete axial compressive strength and the elastic modulus decline gradually. Tensile and compressive meridians of concrete shrink gradually. The research can be referenced for anti-crack design of actual structures eroded by seawater at cold regions.
基金Project(2016M591957) supported by the China Postdoctoral Science FoundationProjects(51878667,51678571)supported by the National Natural Science Foundation of ChinaProject(2017XKQY050) supported by the Fundamental Research Funds for the Central Universities,China。
文摘Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expansive soils,the effectiveness and accuracy of free swelling ratio should be highly required.However,due to the deficiency of geotechnical test regulations for the free swelling ratio test,non-negligible variation difference is often observed among the test results of the same type of soil samples.Thus,a series of laboratory tests are conducted to figure out the influences of soil particle size,initial soil temperature,and wet-dry circulation on the free swelling ratio of expansive soils.The results show that the initial soil temperature exerts an obvious influence on free swelling ratio and a relative weak influence on soil mass of expansive soil with the micro soil particle size(d<0.075 mm),and the correlation becomes unclear when soil particle size is within the range of 0.075 mm≤d<0.500 mm.A larger particle size of expansive soils induces a larger free swelling ratio and soil mass in the soil measuring cup regardless of initial soil temperature.However,the enlarging amplitude decreases as the particle size of expansive soils increases.There is a progressive enlargement of free swelling ratio at the first two wet-dry cycles and then it attenuates gradually when the number of wetdry cycles further increases.
基金Projects(52008003,52074009)supported by the National Natural Science Foundation of ChinaProject(201904a07020081)supported by the Key Research and Development Program Project of Anhui Province,ChinaProject(1908085QE213)supported by the Nature Science Foundation of Anhui Province,China。
文摘To investigate the static compressive properties and mechanical damage evolution of rubber cement-based materials(RCBMs) with dry-and wet-curing conditions, uniaxial compression and cyclic loading-unloading tests were carried out on rubber cement mortar(RCM). The mechanical properties of the uniaxial compression specimens cured at 95%(wet-curing) and 50%(dry-curing) relative humidities and cyclic loading-unloading specimens cured at wet-curing were analyzed. Under uniaxial compression, the peak stress loss ratio is higher for dry-curing than for wet-curing. The peak strain decreases with the increase of rubber content, and the peak strain increases with the decrease of curing humidity. Under cyclic loading-unloading, the variation trends of residual strain differences of the normal cement mortar and RCM at each cyclic level with the number of cycles are basically the same, but the failure modes are different. The analysis of the internal mesostructure by a scanning electron microscope(SEM) shows that initial damage is further enhanced by reducing curing humidity and adding rubber aggregate. The damage constitutive model based on strain equivalence principle and statistical theories was used to describe the uniaxial compression characteristics of RCM, and the law of mechanical damage evolution was predicted.
