EFFECTS OF WATER ABSORPTION AND NEUTRALIZATION PROPERTIES OF CRUSHED SHELL ON STABILIZATION OF ACID SULFATE SOILS

本研究包括两种室内试验和一个现场调查如下：室内试验的第一个目的是阐明pH值上升引起的孔隙水的波动机制，与酸性硫酸盐土壤接触，包括黄铁矿和碳酸钙从牡蛎壳衍生诱导。室内试验的第二个目的是明确酸性硫酸盐土、碎牡蛎壳和稳定剂混合料的承载力和强度特性。一方面，实地调查的预期成果是确定上述混合物在暴露条件下的固化情况，并确定其弹性模量。从化学试验、力学试验和现场测量记录中获得的主要结果概述如下：（1）将碳酸钙和熟石灰混合到酸性硫酸盐土中，由于水吸收反应形成氢氧化铁，孔隙水的量发生变化，脱水反应形成氧化铁，二氧化碳挥发，碳酸钙溶解。（2）酸性硫酸盐土、碎牡蛎壳和稳定剂的混合料的无侧限抗压强度和CBR值均比不加壳块的混合料大。因此，将压碎的牡蛎壳混合到酸性硫酸盐土壤中有助于减少稳定剂的添加剂含量。（3）由酸性硫酸盐土、碎牡蛎壳和稳定剂混合料制成的试件的冲击加速度实测值可知，其承载力随时间的推移而逐渐增大，反分析计算的弹性模量比不加壳块的试件的弹性模量大。

This study consists of two kinds of laboratory tests and a field inventory shown in the following :The first purpose of laboratory tests is to elucidate the fluctuation mechanism of pore water caused by rise of pH which the contact with acid sulfate soil including pyrite and calcium carbonate deriving from the oyster shell induces. The second purpose of laboratory tests is to clarify the bearing capacity and strength characteristics of the mixture of acid sulfate soil, crushed oyster shell and stabilizer. On the one hand, the products expected in a field inventory are the ascertaining of a solidification of the above mixture under exposure condition and the finding of its elastic modulus.The principal results obtained from chemical tests, mechanical experiments and measurement records at in situ are summarized as follows :(1)Mixing a calcium carbonate and slaked lime into acid sulfate soil, the amount of pore water varies due to the water absorption reaction with formation of an iron hydroxide, the dehydration reaction with formation of an iron oxide and the volatilization of carbon dioxide with dissolution of a calcium carbonate.(2)The unconfined compressive strength and CBR value of the mixture of acid sulfate soil, crushed oyster shell and stabilizer have become larger than those of the mixture without shell pieces. Therefore, the mixing of a crushed oyster shell into acid sulfate soil contributes to a reduction in additive content of stabilizer.(3)According to the impact acceleration values measured on sections which have been made by using the mixture of acid sulfate soil, crushed oyster shell and stabilizer, those bearing capacities increase gradually with a passage of time, and those elastic moduli calculated by inverse analysis are greater as compared to sections which have been made by using the mixture without shell pieces.