Microstructure And Mechanical Properties Of Artificially Cemented Red Clay

Free iron oxide colloid in laterite is ubiquitous in natural soil.This type of soil usually has good mechanical properties.With the rapid development of China's economy,laterite is widely used as building foundation and material.Therefore,it is very necessary and urgent to study laterite in depth.In this paper,kaolin and free iron oxide colloid formation of initial artificial cementation laterite as test material,carried out in different colloid content,dry-wet cycles,and curing time for the factors affecting the experiments of laterite,including the unconfined compressive strength and consolidation compression,triaxial shear,nuclear magnetic resonance(NMR),X-ray diffraction and electron microscope scanning test.The changes of compression and shear strength,free iron oxide minerals and microscopic pores,cementation mechanism,cementation influencing factors,cementation dynamic changes,and the relationship between cementation parameters and deformation-strength of laterite were studied in detail.The rule and mechanism of free iron oxide in the process of structural strength formation and strength growth of red clay were discussed.The main conclusions are as follows:1?Artificial laterite samples with single influencing factors were obtained by using uncemented kaolin and single variable ferric hydroxide colloid.The corresponding preparation equipment of artificial red clay was designed.At this time,the artificial red clay is in the initial stage of laterization.The reasons for the different properties of red clay caused by regional differences were solved and explained.2?There is a positive correlation between the plastic index of laterite and the content of mucous grains,and there is a high linear correlation between fractal dimension and soil particle size distribution.The surface area and the liquid limit and plasticity index are fitted by the exponential model.The strain corresponding to the peak shear strength of artificial laterite sample is different from the maximum shear expansion,and when the surrounding pressure is large enough,the main factor of resistance to pressure is soil particles.3?In this paper,the distribution of internal pore size and the variation of pore size and number of artificial red clay samples were studied by NMR test,and the variation of pore size was obtained.The regularity of laterification of red clay is as follows: colloidal content >drying and wetting cycle > curing time.At the same time,the content of free ferric oxide colloid,the number of drying and wetting cycles and the curing time in the "crystallization" degree of red clay during the laterification process are given.The pore volume of red clay increased by 31%,5.6% and 0.35%,respectively,during the laterification of free iron oxide colloid content,number of dry-wetting cycles and curing time.4?The results of artificial laterite mineral analysis show that the morphological change law of free iron oxide mineral is that of iron ore? fiber iron ore ? needle iron ore ?hematite.When the age of maintenance reaches 80 d,needle iron ore and hematite occur.Therefore,the transition between ferric minerals of free ferric oxides helps us reconstruct the paleoclimate evolution during the lateritic formation period.5?The scanning electroscope test found that the pores of the laterite specimen particles were gradually filled with red chemical products with the increase of maintenance age and free iron oxide content,and the contact surface of clay-like bonding increased,while the mineral types of iron also changed,and the content of needle iron ore and hematite increased gradually.Its macro performance increases in cohesion and reduces compression coefficient.6?A quantitative analysis of the macroscopic mechanical strength and microstructure of the structural changes caused by the cementation of laterite is established.The parameters of strain cementation and stress cementation were put forward,and the variation rules of the content of free iron oxide colloid,curing age,number of dry-wet cycles and the cementation parameters were described,so as to describe the relationship between the cementation characteristics and the deformation-strength of laterite.At the same time,the artificial laterite and other soil samples in this paper are normalized to obtain more ideal results and rules.