Study On Microstructure And The Strength Of The Calcareous Hardpan In Calcareous Concretions Soil

Calcareous concretion soil is widely distributed in Huaibei plain, a regionalspecial soil, calcareous hardpan is an important type of calcareous concretion soil.In this paper, based on collecting, reading, finishing engineering geological data ofthe study area, through field geological survey, drilling, in situ test, indoor test,Huaibei plain calcareous hardpan distribution laws, genesis, microstructurecharacteristic and its strength characteristics under the condition of different watercontent has carried on the detailed study.First, collect calcareous concretion soil relevant data, through fieldengineering geological mapping, sampling, selecting typical section of calcareousconcretion soil distribution for field test in situ. Formation process in detail, age,distribution of calcareous hardpan was elaborated, schematic formation ofcalcareous hardpan was plotted. Calcareous hardpan is affected by the action ofgroundwater,which is rich in HCO3--Ca++, long-term eluviation and deposition,using14C dating calcareous hardpan layer dating back16,000to40,000years, themid-to late Late Pleistocene. Select representative samples of cutting sheet andsample preparation, Through the microscope and X ray diffraction test means forcalcareous hardpan microstructure，microscopic observation, analysis, elaboratedthe mineral composition of calcareous hardpan, particle shape, size andarrangement, quantitative analysis of the calcareous hardpan microstructure, suchas the number of particles size, shape, shape coefficient and so on. Select typicalcalcareous hardpan undisturbed samples, prepared into50×50×50mm3square block,according to the different water content (according to the dry and saturated state)subjected to uniaxial compressive strength test of calcareous hardpan samples,discusses the relationship between water content and the uniaxial compressivestrength of Huaibei plain calcareous hardpan; failure mode and mechanism ofcalcareous hardpan compressive strength test is analyzed. At the same time, for thesame set of test samples irregular calcareous concretions hardpan, analyse thecalcareous hardpan failure mechanism in the point load test, the relationshipbetween water content and point load strength; and contrast point loading strengthtest with uniaxial compressive strength test results, statistical analysis. Linearregression method is used to statistical analysis of test result, the results show that both the strength of the test has good correlation. Therefore, in the wild or lack oftest conditions, the point load test can also quickly and accurately determinedcalcareous hardpan strength. Finally, the relationship between the physicalparameters of calcareous hardpan specimens and calcareous hardpan strength isanalysed, the relationship between the calcareous hardpan strength andmicrostructure is discussed. We found that calcareous hardpan size and shape ofthe holes in a large effect on its physical and mechanical properties.