Study On Solidification Process Of Cemented Soil By The Alternating Current Impedance Characteristics

Cemented soil can affectively improve the ground bearing capacity and reduce the foundation settlement. As flexibly designing and conveniently constructing, this technology is applied widely. Therefore studying on cemented soil has important significance in theory and engineering practice. In the past, some researchers used a macro method to test the basic properties of the cemented soil material, but the method needs to destroy the original specimen. It can’t analyze the microscopic structure of the material, and consume a lot of manpower material resources. Gradually, electrical method has been paid more attention to study the microstructure of the material. As porous electrochemical system, the Cement-based materials’change of internal structure can be reflected by that of electrical parameters; therefore the mechanical properties of materials can be studied by the electrical method. However, the electrical method is only at the exploratory stage, there is no unified understanding.Based on linear dynamic system theory and complex function theory, an AC impedance method was proposed in this thesis. This study is expected to change the difficulty to easy. The traditional method is difficult to analyze quantitatively the solid faction process of cemented soil in modern soil mechanics. Fist, mixed soil and water with two types cement (ordinary Portland cement, slag Portland cement), to product the cemented soil blocks; then, measured the AC impedance parameters during the solidification stage. The AC impedance method will lay the foundation for the research of the unconfined compressive strength and durability in research of cement-treated soil. The main conclusions are as follows:(1) The Bode diagrams of ordinary Portland cement and slag Portland cemented soil test blocks vary with the similar rules:the impedance value decrease with increasing frequency. The early impedance is lower and less sensitive to the frequency. When the age range is7days to30days, the impedance of the cemented soil blocks decrease rapidly at first and then vary little with increasing frequency. From60days to90days, the impedance of the cemented soil block is highest at low frequency, however, decrease sharply with the increase of frequency.(2) In the low frequency region, the capacitance value of9hours is maximizing, whereas that of7days reach minimal. In the high frequency region, the capacitance value close to the same value, and then decrease to zero with frequency increasing to1000Hz. (3) As the complexity of the internal structure, cemented soil is not a kind of ideal electrochemical model. Therefore, cemented soil didn’t appear the Randles phenomenon, just quasi Randles phenomenon.(4) The early solidified process can divide into three stages:the dissolving period, the induction period and the hardening period according to the variation trend of AC impedance parameters,|Z|, Z’, Z and θ.(5) Based on the high relationship between the AC impedance parameters and unconfined compression strength, the AC impedance method is expected to become a non-destructive, low-cost, convenient tool for detecting cemented soil.