雅鲁藏布江色东普沟冰崩机理试验研究

doi:10.13745/j.esf.sf.2023.2.64

摘要/Abstract

摘要：

近年来青藏高原地区冰崩灾害事件频发,冰崩成因机理问题备受关注。本文根据色东普沟多期影像数据分析了冰崩灾害演化过程与影响因素,并通过开展不同温度下冰介质剪切试验研究揭示了色东普沟冰崩成因机理。研究结果表明:(1)地形坡度超过30°时易发生冰崩灾害,地震加剧了冰川变形破裂,气候变暖是导致色东普沟冰崩频发的主要原因;(2)重塑多晶冰与冰-岩嵌固体的剪切应力-剪切位移曲线均成“脆性变形型”,在较低的温度条件下重塑多晶冰的剪切应力-剪切变形曲线会出现“二次峰值”;(3)随温度上升,多晶冰样和冰-岩嵌固体的黏聚力与内摩擦角呈直线下降甚至呈加速下降趋势,在相同温度下冰-岩嵌固体的黏聚力小于多晶冰样的黏聚力,而冰-岩嵌固体内摩擦角普遍大于多晶冰样的内摩擦角;(4)温度上升会导致冰川冰或冰-岩嵌固体剪切滑动带的强度衰减,抗滑力下降,从而触发冰崩。

关键词: 冰崩, 成因机制, 演化特征, 剪切试验, 遥感解译, 色东普沟

Abstract:

In recent years ice avalanche disasters occur frequently in the Tibetan Plateau and the mechanism of ice avalanche has attracted much attention. In this paper, the evolutionary process and controlling factors of ice avalanche in the Sedongpu sag were investigated via multi-stage imaging analysis. In the mechanistic study, shear strength tests were carried out at different temperatures on two types of ice materials: crystalline ice and ice-rock mixture. The crystalline ice sample was prepared by pressing crushed ices into a mold, and the ice-rock mixture was prepared by pressing crushed ices and slate. Imaging analysis results showed that glaciers with 30° or steeper terrain slopes were prone to ice avalanche while strong near-field earthquakes aggravated glacier deformation/fracture, and climate warming was the main reason for the frequent occurrence of ice avalanches in the Sedongpu sag. In the shear test, the shear stress-shear displacement curves for both materials revealed brittle deformation type, while for polycrystalline ice a “secondary peak” appeared under low temperature conditions, indicating refreezing phenomenon. With increasing temperature, the cohesive strength and internal friction angle of both materials decreased linearly, even at an accelerated pace; whilst at the same temperature, the cohesive strength was less and the internal friction angle was greater for ice-rock mixture than for polycrystalline ice. Thus the likely genetic mechanism of ice avalanche is that the rise of temperature leads to decrease of shear strength of the ice/rock shear sliding zone thus its anti-sliding force to trigger an ice avalanche.

Key words: ice avalanche, genetic mechanism, evolution characteristics, shear test, interpretation of remote sensing, Sedongpu sag

中图分类号:

P694
P642.2

汤明高, 刘昕昕, 李广, 赵欢乐, 许强, 朱星, 李为乐. 雅鲁藏布江色东普沟冰崩机理试验研究[J]. 地学前缘, 2023, 30(4): 405-417.

TANG Minggao, LIU Xinxin, LI Guang, ZHAO Huanle, XU Qiang, ZHU Xing, LI Weile. Mechanism of ice avalanche in the Sedongpu sag, Yarlung Zangbo River basin-an experimental study[J]. Earth Science Frontiers, 2023, 30(4): 405-417.

图/表 17

图1 色东普流域冰川及松散堆积层分布 1-冰川变形体;2-第四系崩坡积物;3-派乡岩组片麻岩;4-堆积区沟道冲洪积物;5-雪被区;6-雅鲁藏布江;7-色东普流域范围;8-等高线;9-分区界线;10-雪线(2016年12月);11-剖面线。

Fig.1 Distribution of glaciers and loose accumulation layers in the Sedongpu sag

图2 色东普沟冰川垂向分区

Fig.2 Vertical division of the Sedongpu sag

表1 色东普沟碎屑流灾害卫星遥感影像来源

Table 1 Basic experimental parameters for satellite remote sensing image collection of debris flow disaster in the Sedongpu sag

事件	影像时间	影像来源	影像精度	云量/可视程度	波段数	备注
	2012-12-16	Google Earth	约1 m	15%/较好	3
2014年碎屑流事件	2014-10-25	Google Earth	约1 m	<5%/好	3
2014年碎屑流事件	2016-12-22	资源三号-02	2.1 m	0%/好	4	立体像对
2017年10月22日碎屑流堵江事件、 2017年11月3日碎屑流事件	2017-12-16	SPOT	1.5 m	0%/好	4	近红外波段
2017年12月21日碎屑流堵江事件	2017-12-28	Planet4	3.8 m	0%/好	4	近红外波段
2018年1月碎屑流堵江事件	2018-01-29	Planet4	3.8 m	10%~15%/较好	4	近红外波段
2018年7月26日碎屑流事件	2018-9-19	Planet4	3.8 m	30%/一般	4	近红外波段
2018年10月17日碎屑流堵江事件、 2018年10月29日碎屑流堵江事件	2018-10-30	Planet4	3.8 m	15%/较好	4	近红外波段
2018年10月17日碎屑流堵江事件、 2018年10月29日碎屑流堵江事件	2018-11-30	资源三号-02	2.1 m	5%/好	4	立体像对

图3 色东普沟冰崩灾害演化过程

Fig.3 Evolutionary stages (stages A-E) of a typical ice avalanche disaster event in the Sedongpu sag

图4 色东普沟坡度分区统计 1-冰川变形体;2-研究区界线;3-分区界线。

Fig.4 Sedongpu sag slope zoning statistics

表2 色东普流域冰川坡度信息统计

Table 2 Slope parameters of glaciers in the Sedongpu sag

冰川分区	冰川编号	平均坡度	坡度超过30°面积占比
①	SDP1	27.66°	26.05%
②	SDP2-a	57.66°	50.00%
	SDP2-b	43.80°	45.16%
	SDP2-c	37.87°	44.32%
	SDP2-d	31.0°	35.63%
	SDP2-e	20.27°	13.20%
③	SDP3-a	20.02°	19.67%
	SDP3-a残余	34.61°	45.7%
	SDP3-b	39.51°	46.75%
④	SDP4	26.38°	27.14%
⑤	SDP5	18.52°	8.28%
⑥	SDP6	29.08°	30.91%
⑦	SDP7	16.15°	3.64%
⑧	SDP8	27.16°	24.95%
⑨	SDP9	25.41°	17.90%

图5 林芝气象站2017-2018年气温、降雨以及冰崩分布

Fig.5 Annual variation of temperature, rainfall and ice avalanche occurrence at the Nyingchi meteorological station between 2017-2018

图6 重塑多晶冰(左)与冰-岩嵌固体(右)

Fig.6 Polycrystalline ice (left) and ice-rock mixture (right) samples

图7 YDS-2型携带式岩土力学性质多功能试验仪 a-剪切仪;b-数据采集系统;c-位移传感器;d-压力传感器。

Fig.7 Experimental setup for the YDS-2 Portable Multifunctional Tester for Rock and Soil Mechanical Properties

图8 剪切完成后试样 a-重塑多晶冰;b-冰-岩嵌固体。

Fig.8 Sample appearance characteristics after shearing

图9 不同温度下重塑多晶冰剪切应力-剪切位移曲线

Fig.9 Shear stress-shear displacement curves for polycrystalline ice at different temperatures a-0.5 ℃;b-10 ℃;c-20 ℃;d-30 ℃;e-40 ℃。

图10 不同温度下冰-岩嵌固体剪切应力-剪切位移曲线

Fig.10 Shear stress-shear displacement curves for ice-rock mixture at different temperatures a-0.5 ℃;b-10 ℃;c-20 ℃;d-30 ℃;e-40 ℃。

图11 不同温度下重塑多晶冰、冰-岩嵌固体抗剪强度参数变化 a-重塑多晶冰;b-冰-岩嵌固体。

Fig.11 Shear strength changes in polycrystalline ice and ice-rock mixture at different temperatures

图12 冰崩体简化滑移模型

Fig.12 A simplified model of avalanche ice sliding

图13 冰崩介质不同受力条件下变形-时间曲线

Fig.13 Deformation-time curves for ice-rock materials during ice avalanche under different sliding forces

图14 冰崩介质不同温度条件下变形-时间曲线

Fig.14 Deformation-time curves for ice-rock materials during ice avalanche under different temperatures

图15 温度升高冰崩变形模式

Fig.15 Deformation stages of ice material with temperature rise leading to avalanche

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