华南风化土崩岗的孕育形成本因与灾变破坏机理研究

Slump gully, one of the geological erosion disasters, is referred to as an ecological ulcer. Considering that the slump gully frequently occurs, and only the symptoms are treated without tracking the disaster mechanism that treatment is intractable at present. This program will be carried out by the combining methods of soil science, soil mechanics and disaster geology and ideas of "macro-disaster + meso-formation + micro-gestation → mechanism → application" in the following. Firstly, research on the formative environment and driving factors such as geologic structure and climate impacts of slump gully from the macro-scale will be performed. Secondly, source properties and main controlling factors such as the physicochemical composition and characteristics of weathered soils from meso-scale will be studied. Taking into account the special characteristics of fissure, softening and disintegration when encountering water, this program plans to conduct slaking tests and disintegration tests. Thirdly, the evolution and failure of soil structure related to the distribution of fissures and pores from micro-scale. Consequently, the incubation cause of the slump gully and its damage mechanism will be revealed essentially, the rule of shearing strength reduction during the process of the disaster will be evaluated, and the controlling and impact factors of its formation and development will be explored. Furthermore, the sensitivity and correlation analyses of each factor are built in trans-dimension, and a hazard evaluation method is proposed based on the soil properties of slump gully, which provides scientific basis for the forecast, controlling measures and comprehensive treatment of the slump gully disaster.

崩岗属一种地质侵蚀灾害，被学术界称为"生态溃疡"。项目针对华南地区崩岗灾害频发、其机理认知不清、治理存在"治标不治本、久治不愈"的现状为背景，通过土质学、土力学与灾害地质学结合的研究方法，采用"宏观地质+中观土性+微观演化+气候影响→机理→应用"的研究思路，以风化土的裂隙性、遇水软化、易崩解性为出发点，结合炎热多雨气候影响，设计湿化试验与浸水崩解试验，从地质构造、气候影响等宏观尺度研究崩岗的孕育环境与驱动因素；从风化土的物化组成、岩土特性等中观尺度研究崩岗的物源性质与控制影响，从裂隙、孔隙分布等微观尺度研究崩岗灾害破坏的结构演化反映，从本质上揭示崩岗的孕育形成本因与灾变破坏机理，评价崩岗灾变过程中土体抗剪强度减损规律，探寻崩岗形成与发展的主控因素与致灾因子，进行跨尺度下各因子的敏感性与关联性分析，提出基于岩土本性分析的崩岗灾害评价方法，为崩岗灾害的预测预报、控制对策及综合治理提供科学依据。

项目以崩岗灾害业已成为华南地区水土保持与灾害防护的突出与亟待解决的重要问题，而其根本机理认知不清、治理存在“治标不治本、久治不愈”的现状为背景，采用土质学、土力学与灾害地质学结合的研究方法，首先对我国福建厦门、海南岛三亚、广东的台山与徐闻以及津巴布韦的花岗岩、玄武岩和泥岩的风化土开展工程地质特征与岩土特性调查，重点调查了台州市龙门水库的大型崩岗群，从地质构造、气候影响等宏观尺度研究崩岗的孕育环境与驱动因素；从风化土的物化组成、岩土特性等细观尺度研究崩岗的物源性质与控制影响，分析了多种风化土的裂隙性、遇水软化、易崩解性对崩岗形成与破坏的影响机制。研究表明，华南地区的风化岩土的基本性质与一般流水沉积的黏土与砂土有明显差别，一些特征指标甚至超出当前规范、规程对一般土质界定的取值范围，同时具有强裂隙性、易扰动、易崩解、遇水软化特性，而且这些特殊性质对气候变化有更高的敏感性，反映出强烈风化导致土体特殊的颗粒成分与结构特征是崩岗孕育形成的内因，该区炎热多雨的气候是崩岗灾频发的外因，并基于研究成果提出了风化土崩解的分类体系与灾变前兆识别信息。此外，项目实施过程中还发现风化土的遇水软化特性还会造成华南地区桩端土遇水软化的工程问题，并对此进行了研究，也提出了风化土的原位指标测试建议与强度识别方法。本研究为深入了解我国华南地区的风化岩土的工程地质特性提供了必要的研究基础，也为该区崩岗灾害的预测预报、控制对策及综合治理提供了科学依据。