丹霞地貌岩体差异胀缩特征及其成景作用

Differential Expansion and Contraction Characteristics of Danxia Landform Rock Mass and Its Geomorphological Effect

丹霞地貌的研究主要以地质构造、地层岩性、外动力条件等宏观方面为主,但这些因素是地质景观形成的普遍性因素,未能较好解释丹霞地貌景观个体特征差异性原因。龙虎山丹霞地貌区岩性物质成分复杂,种类较多。本文从微观的角度,分析其岩体差异胀缩在丹霞地貌景观成因中的作用。选取研究区主要的6类物质成分岩块,在热、水、热-水三种条件下进行膨胀性试验,得出热膨胀率最大相差2.58倍,水膨胀率相差3.54倍,热-水膨胀率相差3.88倍。由于物质成分的差异性,当外界环境条件变化时,岩体内物质发生差异性胀缩。这种差异性胀缩引起岩体表面细粒物、砾石脱落,形成凹凸形态,构成了丹霞地貌成景的基础元素。研究区胀缩引起的凹凸形态,主要形成"脸型""头型"和"身型"三类丹霞地貌景观。

The research on Danxia landform is mainly based on macroscopic aspects such as geological structure,stratum lithology and external dynamic conditions,but these factors are the universal factors for the formation of geological landscape,which fails to explain the differences in individual characteristics of Danxia landscapes.The lithologic composition of the Danxia landform area in Longhushan at Yingtang country,Jiangxi province,China is complex and has many types.From the microscopic point of view,this paper analyzed the role of the differential expansion and contraction of rock mass in the genesis of Danxia landform.The main six types of rock masses in the study area were selected,and expansion tests were carried out under the conditions of heating,water soaking and hydrothermal treatments.The maximum thermal volumetric expansion rate was 2.58 times.The water volumetric expansion rate was 3.54 times,and similarly the thermal-water volumetric expansion rate was obtained.The difference in expansion rate between water condition and heat condition was 3.88 times.Due to the differences in material composition,when the external environmental conditions changed,the material in the rock body underwent differential expansion and contraction,causing the fine particles and gravel on the surface of rock mass to fall off and then to form a concave and convex shape,which constituted the basic element of the Danxia landform in Longhushan.In the study area there are mainly three types of Danxia landforms,“face shape”,“head shape”and“body shape”.This paper provides a perspective from the volumetric expansion coefficient of sediments in red beds to study micro-geomorphology of Danxia landforms.