干湿交替对长江荆江段典型断面岸滩土体力学性能的影响
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摘要
河道水位水文年内的动态变化使得河岸土体处于干湿交替的状态。为研究干湿交替对粘性岸滩土体力学性能及河岸稳定性的影响,以长江荆江段8个典型崩岸断面岸滩的粘性土体为研究对象。采用历史资料分析、实地勘察取样、室内土工试验、BSTEM模型模拟相结合的方法,分析了上、下荆江河岸土体组成及力学特性,并且定量研究了干湿交替条件下粘性岸滩土体力学性能的变化;运用BSTEM模型对荆61和北门口断面在2013水文年内的崩岸过程进行了模拟,并分析了干、湿条件下土体抗剪强度指标对河岸稳定性的影响。结果表明:随着土体含水率的增加,粘聚力先增大后减小,而内摩擦角呈指数关系减小,并得出含水率与粘聚力和内摩擦角的定量关系式;2个断面计算崩塌宽度与实际一致,误差分别为1.69%和3.74%;干湿交替情况下安全系数值主要受土体粘聚力值的影响,并分别得到了2个典型断面粘聚力和内摩擦角与安全系数的一元线性关系。这样已知河岸土体含水率时,就可以通过关系式计算得出土体的粘聚力和内摩擦角,从而得出安全系数,判断河岸稳定性。
The dynamic change of water level in a hydrological year can keep riverbank soil in the state of alternating dry and wet. The variety of water content of riverbank soil can change the mechanical properties of soil to a certain extent, which can affect riverbank stability. In order to investigate quantitatively the influence of dry-wet alternation condition on mechanical properties of riverbank clay soil, a field observation and sampling were first conducted at eight typical riverbanks in upper and lower Jingjiang Reach, which the clay soil of the typical riverbanks in Jingjiang Reach of the Yangtze River was taken as the study area. Through a comprehensive analysis of measured data, indoor soil tests and BSTEM simulation, the composition and mechanical properties of these samples were obtained, which indicated that the vertical soil composition of riverbank was characterized by a typical composite structure of non-cohesive lower bank and cohesive upper bank. The indoor soil test results revealed the quantitative change of soil mechanics with dry-wet alternation condition, and a close relationship between water content and shear strength indicators was obtained. With an increase of water content, the cohesion first increased and then decreased, with the peak values of 21 kPa and 34 kP a for the critical water content of 16.0% and 22.8% at Jing 61 and Beimenkou sections, and eventually reached a constant, while internal friction angel decreased significantly. Considering the dry-wet alternation condition of riverbank soil and the change of river water level in a hydrological year, the degrees of riverbank stability at Jing 61 and Beimenkou sections were analyzed during four different water level periods using BSTEM, and the process of bank failure of two sections were simulated in 2013. The results indicated that: the model-predicted results of the total bank retreat width were in close agreement with the measured data with the relative errors 1.69% and 3.74%, respectively. At the same time, the safety factors under different dry and wet conditions were calculated based on the BSTEM simulated results of two typical sections. The relationship between safety factor and water content was obtained, which indicated the safety factor first increased and then decreased with an increase of water content. It was consistent with the relationship between soil cohesive and water content which proved that the soil cohesive has an important influence on the stability of river bank. Quantitative relationships between safety factors and cohesive and internal friction angle of two typical sections were identified, respectively, and the correlation coefficients were 0.980 and 0.876 for Jing 61 section, and 0.992 and 0.986 for Beimenkou section, respectively. The relationships between them were linear function from which the safety factors increased with the increase of the cohesive and internal friction angle, respectively. Thus, a conclusion can be drawn that the safety factor was mainly affected by soil cohesive under different dry and wet conditions. For actual project, when water content of the riverbank soil was obtained, the cohesive and internal friction angle of soil can be calculated by proposed formulas, thereby the safety factor of riverbank can be calculated and the stability of river bank can be identified.
The dynamic change of water level in a hydrological year can keep riverbank soil in the state of alternating dry and wet. The variety of water content of riverbank soil can change the mechanical properties of soil to a certain extent, which can affect riverbank stability. In order to investigate quantitatively the influence of dry-wet alternation condition on mechanical properties of riverbank clay soil, a field observation and sampling were first conducted at eight typical riverbanks in upper and lower Jingjiang Reach, which the clay soil of the typical riverbanks in Jingjiang Reach of the Yangtze River was taken as the study area. Through a comprehensive analysis of measured data, indoor soil tests and BSTEM simulation, the composition and mechanical properties of these samples were obtained, which indicated that the vertical soil composition of riverbank was characterized by a typical composite structure of non-cohesive lower bank and cohesive upper bank. The indoor soil test results revealed the quantitative change of soil mechanics with dry-wet alternation condition, and a close relationship between water content and shear strength indicators was obtained. With an increase of water content, the cohesion first increased and then decreased, with the peak values of 21 kPa and 34 kP a for the critical water content of 16.0% and 22.8% at Jing 61 and Beimenkou sections, and eventually reached a constant, while internal friction angel decreased significantly. Considering the dry-wet alternation condition of riverbank soil and the change of river water level in a hydrological year, the degrees of riverbank stability at Jing 61 and Beimenkou sections were analyzed during four different water level periods using BSTEM, and the process of bank failure of two sections were simulated in 2013. The results indicated that: the model-predicted results of the total bank retreat width were in close agreement with the measured data with the relative errors 1.69% and 3.74%, respectively. At the same time, the safety factors under different dry and wet conditions were calculated based on the BSTEM simulated results of two typical sections. The relationship between safety factor and water content was obtained, which indicated the safety factor first increased and then decreased with an increase of water content. It was consistent with the relationship between soil cohesive and water content which proved that the soil cohesive has an important influence on the stability of river bank. Quantitative relationships between safety factors and cohesive and internal friction angle of two typical sections were identified, respectively, and the correlation coefficients were 0.980 and 0.876 for Jing 61 section, and 0.992 and 0.986 for Beimenkou section, respectively. The relationships between them were linear function from which the safety factors increased with the increase of the cohesive and internal friction angle, respectively. Thus, a conclusion can be drawn that the safety factor was mainly affected by soil cohesive under different dry and wet conditions. For actual project, when water content of the riverbank soil was obtained, the cohesive and internal friction angle of soil can be calculated by proposed formulas, thereby the safety factor of riverbank can be calculated and the stability of river bank can be identified.
引文
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[20]宗全利,夏军强,张翼,等.荆江段河岸粘性土体抗冲特性试验[J].水科学进展,2014(4):567-574.Zong Quanli,Xia Junqiang,Zhang Yi,et al.Experimental study on scouring characteristics of cohesive bank soil in the Jingjiang reach[J].Advances in Water Science,2014(4):567-574.(in Chinese with English abstract)
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[22]夏军强,宗全利,邓珊珊,等.三峡工程运用后荆江河段平滩河槽形态调整特点[J].浙江大学学报:工学版,2015(2):238-245.Xia Junqiang,Zong Quanli,Deng Shanshan,et al.Adjustments in reach-scale bankfull channel geometry of Jingjiang reach after operation of Three Gorges Project[J].Journal of Zhejiang University:Engineering Science,2015(2):238-245.(in Chinese with English abstract)
[23]张翼,夏军强,宗全利,等.下荆江二元结构河岸崩退过程模拟及影响因素分析[J].泥沙研究,2015(3):27-34.Zhang Yi,Xia Junqiang,Zong Quanli,et al.Modeling of the failure process of a composite riverbank and influencing factors analysis in the Lower Jingjiang Reach[J].Journal of Sediment Research,2015(3):27-34.(in Chinese with English abstract)
[24]李洁,夏军强,邓珊珊,等.近期黄河下游游荡段滩岸崩退过程及特点[J].水科学进展,2015(4):517-525.Li Jie,Xia Junqiang,Deng Shanshan,et al.Recent bank retreat processes and characteristics in the braided reach of the Lower Yellow River[J].Advances in Water Science,2015(4):517-525.(in Chinese with English abstract)
[25]黄本胜,白玉川,万艳春.河岸崩塌机理的理论模式及其计算[J].水利学报,2002,33(9):49-54.Huang Bensheng,Bai Yuchuan,Wan Yanchun.Model for dilapidation mechanism of riverbank[J].Journal of Chinese Hydraulic Engineering,2002,33(9):49-54.(in Chinese with English abstract)
[26]刘黎明,段光磊.荆江文村夹堤岸近岸河床演变分析[J].水利水电快报,2003,24(22):21-24.Liu Liming,Duan Guanglei.Analysis on near bank riverbed evolvement of Jingjiang Wencunjia[J].Express Water Resources and Hydropower Information,2003,24(22):21-24.(in Chinese with English abstract)
[27]姚仕明,岳红艳,何广水,等.长江中游河道崩岸机理与综合治理技术[M].北京:科学出版社,2016.
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[31]王博,姚仕明,岳红艳.基于BSTEM的长江中游河道岸坡稳定性分析[J].长江科学院院报,2014,31(1):1-7.Wang Bo,Yao Shiming,Yue Hongyan.Stability analysis for typical riverbank slope in the middle reach of Yangtze River by BSTEM[J].Journal of Yangtze River Scientific Research Institute,2014,31(1):1-7.(in Chinese with English abstract)
[2]钱宁,张仁,周志德.河床演变学[M].北京:科学出版社,1987:584.
[3]Osman A M,Thorne C R.Riverbank stability analysis I:Theory[J].Journal of Hydraulic Engineering,1988,114(2):134-150.
[4]Robert G M,Michael C Q.Effect of bank stabi1ity on geometry of gravel rivers[J].Journal of Hydraulic Engineering,1993,119(12):1343-1363.
[5]Simon A,Curini A,Darby S E,et al.Bank and near-bank processes in an incised channel[J].Geomorphology,2000,35:193-217.
[6]Simon A,Collison A J C.Quantifying the mechanical and hydrologic effects of riparian vegetation on stream-bank stability[J].Earth Surface Processes and Land Forms,2002,27(5):527-546.
[7]余文畴,卢金友.长江河道崩岸与护岸[M].北京:中国水利水电出版社,2008:260.
[8]饶庆元.粘性土抗冲特性研究[J].长江科学院院报,1987(4):73-84.Rao Qingyuan.A study on the characteristics of clay[J].Journal of Yangtze River Scientific Research Institute,1987(4):73-84.(in Chinese with English abstract)
[9]夏军强,吴保生,王艳平,等.黄河下游游荡段滩岸土体组成及力学特性分析[J].科学通报,2007(23):2806-2812.
[10]杨进良.土力学(第4版)[M].北京:中国水利水电出版社,2009.
[11]岳红艳,姚仕明,朱勇辉,等.二元结构河岸崩塌机理试验研究[J].长江科学院院报,2014,31(4):26-30.Yue Hongyan,Yao Shiming,Zhu Yonghui,et al.Experimental research on the mechanism of binary riverbank collapse[J].Journal of Yangtze River Scientific Research Institute,2014,31(4):26-30.(in Chinese with English abstract)
[12]唐金武,邓金运,由星莹,等.长江中下游河道崩岸预测方法[J].四川大学学报:工程科学版,2012,44(1):75-81.Tang Jinwu,Deng Jinyun,You Xingying,et al.Forecast method for bank collapse in middle and lower Yangtze River[J].Journal of Sichuan University:Engineering Science Edition,2012,44(1):75-81.(in Chinese with English abstract)
[13]假冬冬,张兴农,应强,等.流滑型崩岸河岸侧蚀模式初探[J].水科学进展,2011,22(6):813-817.Jia Dongdong,Zhang Xingnong,Ying Qiang,et al.Preliminary study on the analytical model for slide collapse of riverbanks[J].Advances in Water Science,2011,22(6):813-817.(in Chinese with English abstract)
[14]假冬冬,邵学军,张幸农,等.水沙调节后荆江典型河道横向调整过程的响应:Ⅰ:二、三维耦合模型的建立[J].水科学进展,2013,24(1):82-87.Jia Dongdong,Shao Xuejun,Zhang Xingnong,et al.Responses of channel migration to changes of flow and sediment regime in Jingjiang segment of the middle Yangtze River:I:2-D and 3-D coupled model[J].Advances in Water Science,2013,24(1):82-87.(in Chinese with English abstract)
[15]夏军强,邓珊珊,周美蓉.荆江河段崩岸机理及多尺度模拟方法[J].人民长江,2017,48(19):1-11.Xia Junqiang,Deng Shanshan,Zhou Meirong.Bank collapse mechanism of Jingjiang River reach and multi-scale simulation[J].Yangtze River,2017,48(19):1-11.(in Chinese with English abstract)
[16]杨怀仁,唐日长.长江中游荆江变迁研究[M].北京:中国水利水电出版社,1999:245.
[17]高志斌,段光磊.边界条件对三峡坝下游河床演变影响[J].人民长江,2006,37(12):92-94.
[18]宗全利,夏军强,许全喜,等.上荆江河段河岸土体组成分析及岸坡稳定性计算[J].水力发电学报,2014(2):168-178.Zong Quanli,Xia Junqiang,Xu Quanxi,et al.Soil composition analysis and slope stability calculation of riverbanks in the Upper Jingjiang Reach[J].Journal of Hydroelectric Engineering,2014(2):168-178.(in Chinese with English abstract)
[19]宗全利,夏军强,邓春艳,等.基于BSTEM模型的二元结构河岸崩塌过程模拟[J].四川大学学报:工程科学版,2013,45(3):69-78.Zong Quanli,Xia Junqiang,Deng Chunyan,et al.Modeling of the composite bank failure process using BSTEM[J].Journal of Sichuan University:Engineering Science Edition,2013,45(3):69-78.(in Chinese with English abstract)
[20]宗全利,夏军强,张翼,等.荆江段河岸粘性土体抗冲特性试验[J].水科学进展,2014(4):567-574.Zong Quanli,Xia Junqiang,Zhang Yi,et al.Experimental study on scouring characteristics of cohesive bank soil in the Jingjiang reach[J].Advances in Water Science,2014(4):567-574.(in Chinese with English abstract)
[21]夏军强,宗全利,许全喜,等.下荆江二元结构河岸土体特性及崩岸机理[J].水科学进展,2013(6):810-820.Xia Junqiang,Zong Quanli,Xu Quanxi,et al.Soil properties and erosion mechanisms of composite riverbanks in Lower Jingjiang Reach[J].Advances in Water Science,2013(6):810-820.(in Chinese with English abstract)
[22]夏军强,宗全利,邓珊珊,等.三峡工程运用后荆江河段平滩河槽形态调整特点[J].浙江大学学报:工学版,2015(2):238-245.Xia Junqiang,Zong Quanli,Deng Shanshan,et al.Adjustments in reach-scale bankfull channel geometry of Jingjiang reach after operation of Three Gorges Project[J].Journal of Zhejiang University:Engineering Science,2015(2):238-245.(in Chinese with English abstract)
[23]张翼,夏军强,宗全利,等.下荆江二元结构河岸崩退过程模拟及影响因素分析[J].泥沙研究,2015(3):27-34.Zhang Yi,Xia Junqiang,Zong Quanli,et al.Modeling of the failure process of a composite riverbank and influencing factors analysis in the Lower Jingjiang Reach[J].Journal of Sediment Research,2015(3):27-34.(in Chinese with English abstract)
[24]李洁,夏军强,邓珊珊,等.近期黄河下游游荡段滩岸崩退过程及特点[J].水科学进展,2015(4):517-525.Li Jie,Xia Junqiang,Deng Shanshan,et al.Recent bank retreat processes and characteristics in the braided reach of the Lower Yellow River[J].Advances in Water Science,2015(4):517-525.(in Chinese with English abstract)
[25]黄本胜,白玉川,万艳春.河岸崩塌机理的理论模式及其计算[J].水利学报,2002,33(9):49-54.Huang Bensheng,Bai Yuchuan,Wan Yanchun.Model for dilapidation mechanism of riverbank[J].Journal of Chinese Hydraulic Engineering,2002,33(9):49-54.(in Chinese with English abstract)
[26]刘黎明,段光磊.荆江文村夹堤岸近岸河床演变分析[J].水利水电快报,2003,24(22):21-24.Liu Liming,Duan Guanglei.Analysis on near bank riverbed evolvement of Jingjiang Wencunjia[J].Express Water Resources and Hydropower Information,2003,24(22):21-24.(in Chinese with English abstract)
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