通过连续3 a对荆江崩岸情况进行现场调查、室内土工试验和概化模型试验,分析荆江崩岸特点及规律、河岸上部黏性土的物理及力学性能以及二元结构河岸崩塌过程的特点和影响因素。结果表明:荆江段崩岸分布规律主要表现为下荆江多于上荆江,左岸多于右岸;二元结构河岸崩塌过程可概括为坡脚受冲刷变陡,岸顶裂缝形成发育,岸坡渐进侵蚀,河岸失稳导致崩塌,岸坡形态趋于稳定,进入下一次河岸崩塌循环;黏性土含水率对水位变化的响应速度快于对浸泡时长的响应速度;黏性土的起动切应力为0.531 N/m2,影响黏聚力值的临界含水率约为16%,受纵向水流及土体含水率的影响,岸坡在枯水期稳定性较高,在涨水期会产生局部崩岸,洪水期和退水期时坡脚冲刷和崩岸强烈。
Abstract
The characteristics of bank collapse of Jingjiang Reach and the physical and mechanical properties of cohesive soil in the upper part of the riverbank are studied based on field investigation, indoor geotechnical test and collapse model test in different hydrological periods for three consecutive years. The characteristics and influencing factors of the bank collapse process of composite structure are also examined. Results reveal that bank collapses occurred more frequently in lower Jingjiang Reach than those in the upper reach, and on left bank more than those on the right bank. The composite structure of riverbank undergone a process generalized as follows: the slope toe becomes steeper due to scouring, cracks occur and develop on bank top, the bank slope is eroded progressively, and bank instability leads to collapse, then the bank slope shape tends to be stable, and finally enters the next collapse cycle. The moisture content of cohesive soil responds more quickly to water level change than that to soaking time. The incipient shear stress of cohesive soil is 0.531 N/m2, and the critical moisture content affecting the cohesion value is about 16%. Affected by longitudinal flow and soil moisture content, the bank slope is of high stability in dry season, but is subjected to local collapse during water level rising; both the flood season and recession stage will see intense slope toe scouring and bank collapse.
关键词
二元结构河岸 /
崩岸试验 /
力学性能 /
抗剪强度 /
含水率 /
荆江
Key words
composite riverbank /
collapse test /
mechanical properties /
shear strength /
moisture content /
Jingjiang Reach
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基金
国家重点研发计划项目(2019YFC1510704);三峡后续项目(CKSG2022095/HL);国家自然科学基金项目(51479008,41906149)
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