Study On Damaged Remodeling Expansive Soil With CT-triaxial Apparatus And Three-dimensional Reconstruction Of CT Images

With the rapid development of our national economic construction, more and more highways, railways and water conservancies are built on the swelled ground. The fracture is an important structure feature of expansive soils, and it has a significant influence for the mechanical properties of expansive soils. The description of three-dimensional configuration for the fracture of expansive soils has not been resolved so far. In order to observe the development and change of interior fracture more intuitively, accurately and conveniently, which is produced in the external load, we designed the CT triaxial test method basing on three-dimensional reconstruction.The expansive soil was researched in this paper, which was taken from the head of diversion canal in south-to-north water transfer project of Tao Cha. The main research contents include that:(1)To prepare the expansive soils samples with artificially holes of different sizes and different positions. Via the artificial holes of different sizes and different positions in the expansive soils samples, we imitated the damage of soils for structure and strength, such as the botanic rootstock and earthworm.(2)CT-triaxial compression test:In the workstation combined by Logistics Engineering Institute and Nan Zheng Hospital, we had triaxial compression testes in the condition of three net confining pressures and two suctions. The change rule of ME and SD value was particular analyzed, and we researched the change rule of pore-damage in different loads.(3)The three-dimensional reconstruction of CT images:We developed the three-dimensional reconstruction program basing on intersected marching cubes algorithm, completed the three-dimensional reconstruction of CT images in different conditions and extracted the particular parts quantitatively (for example, holes). We reproduced the internal three-dimensional evolution of soil samples in loading procedure, and broke through the boundedness which only analyzed the change rule of planer structure in the past. The main conclusion includes:(1) When the net confining pressure and suction remain unchanged, axial strain of samples under different conditions can increase when deviatoric stress reduces.(2) 3D model of the three-dimensional reconstruction procedure shows the evolution law of appearance and internal structure of samples in different conditions.(3) If time is regarded as one dimensionality and it can show evolution law consecutively in the process of shearing the samples, the effects will be more intuitionistic, and this four-dimensional reconstruction procedure can be researched further.The structural characteristics and mechanical property of expansive soils are researched in this paper more roundly. It is important for further studying the mechanism of fracture and mechanical mechanism of roadbed and side slope on the swelled ground. Simultaneously, this method also can be applied to other CT experimental studies of constructional geotechnical material.