| Cement soil is widely used in engineering construction as a convenient and economical construction material,but in actual engineering,influenced by climatic conditions and geological environment,the cement soil is often subject to the effects of dry-wet cycles,sulfate erosion,etc.,which makes its performance reduced.The paper conducted the unconfined compressive strength test of the cement soil with different doping amounts of basalt fiber(0,0.5%,1.0%,1.5%,2.0%,2.5%)and fly ash(0,4%,8%,12%,16%,20%)to obtain the optimal doping amounts of basalt fiber and fly ash;On this basis,carry out different dry-wet cycles(3,7,14,28)and different Na2SO4 concentrations(1.5g/L,4.5g/L,9.0g/L,18.0g/L),different erosion time(3d,7d,14d,28d)unconfined compressive strength test and impact dynamics(SHPB)test of cement-soil specimens.The main research contents and results are:(1)The unconfined compressive strength tests were carried out on the cement soil specimens of basalt fiber and fly ash with different doping amounts.The results showed that with the increase of basalt fiber and fly ash doping,the unconfined compressive strength of the cement soil specimens showed a trend of first increase and then decrease.It indicates that the appropriate amount of basalt fiber and fly ash can effectively improve the mechanical properties of the cement soil.The unconfined compressive strength of the cement soil specimens reached the maximum value of 5.80 MPa when the basalt fiber dose was 1.0%and the fly ash dose was 12%,which increased 46.32%compared with the plain cement soil specimens.(2)The basalt fiber fly ash cement soil specimens were tested for unconfined compressive strength under different numbers of dry-wet cycles(3,7,14,28),while the quality and wave velocity of the cement soil specimens before and after the dry-wet cycles were tested.The test results showed that the mass loss rate,relative wave velocity and unconfined compressive strength of the cement soil specimens increased gradually with the increase of the number of dry-wet cycles.The unconfined compressive strength of the cement soil specimens reached the maximum value of 6.35MPa when the number of drywet cycles was 7.(3)Conduct different erosion time(3d,7d,14d,28d)tests on cement soil specimens soaked in water and different Na2SO4 solution concentrations(1.5g/L,4.5g/L,9.0g/L,18.0g/L)to investigate the effects of sulfate concentration and erosion time on the mass change rate,wave velocity,stress-strain relationship and unconfined compressive strength of the cement soil.The test results showed that the mass change rate,relative wave velocity,and unconfined compressive strength of the cement specimens showed a trend of increasing and then decreasing with the increase of Na2SO4 concentration and erosion time;when the Na2SO4 concentration was 9.0g/L and the erosion time was 14d,the unconfined compressive strength of the cement specimens reached the maximum value of 8.49MPa.(4)The SHPB test system was used to conduct impact dynamic tests on cement soil specimens subjected to different numbers of dry-wet cycles(3,7,14,28).The test results showed that the dynamic compressive strength and absorbed energy of the cement specimens showed an increasing trend with the increase of the number of dry-wet cycles;The dynamic compressive strength and absorbed energy reached the maximum value of 14.97MPa and 10.73J when the number of dry-wet cycles was 7.(5)The SHPB test system was used to conduct impact dynamic tests on cement soil specimens soaked in water and different Na2SO4 concentrations(1.5g/L,4.5g/L,9.0g/L,18.0g/L)of sulfate solution after eroding for 3d,7d,14d and 28d.Investigating the effects of sulfate concentration and erosion time on the dynamic stress-strain,dynamic compressive strength and absorbed energy of the cement soil specimens under impact loading.The test results showed that the dynamic compressive strength and absorbed energy of the cement specimens showed a trend of increasing and then decreasing with the increase of Na2SO4 concentration and erosion time;the dynamic compressive strength and absorbed energy of the cement soil specimens reached the maximum values of 21.29MPa and 16.53J when the Na2SO4 concentration was 9.0g/L and the erosion time was 14d.(6)SEM tests and X-ray diffraction tests were conducted on the hydroclay specimens after 14d of erosion with water and different concentrations of Na2SO4 solutions(4.5g/L,9.0g/L,18.0g/L),the microstructure analysis and and physical phase analysis were carried out.The test results showed that with the increase of Na2SO4 concentration,the ettringite,albite and anorthite inside the cement soil specimen gradually increased,and the pores inside the specimen gradually decreased,which was beneficial to the increase of its macro-mechanical strength;however,when the sulfate concentration reached 18.0g/L,micro-cracks were generated inside the specimen,which would adversely affect the subsequent macro-mechanical strength.Figure [40] Table [16] Reference [74]... |
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