水流冲刷作用下单体土工袋稳定特性试验研究

Experimental study on the stability characteristics of single geobag under the action of water flow scouring

【目的】为探究水流冲刷作用下单体土工袋在河流护岸结构中护底处的稳定规律,【方法】基于塔里木河土工袋护岸工程,搭建水槽模型试验平台,制作了不同规格土工袋模型。讨论Robin体积公式在实际工程应用中的不足。基于土工袋试验结果,分析了土工袋充填率、长宽比、下垫面糙率、摆放形式等实际工程中重点关注因素与稳定性的响应规律。【结果】试验结果显示:土工袋所受推力FD随充填率的增加而逐渐增大,升力FL随充填率的增大先增大后减小;长宽比大于2.33时,土工袋顺水流放置时稳定性逐渐降低,而垂直水流放置时,土工袋稳定性随长宽比的增加一直降低;通过改变土工袋与下垫面的糙率可有效提高土工袋的稳定性。【结论】结果表明:充填率通过直接影响装填后土工袋有效受力面积,进而影响使土工袋失稳的FD和FL的大小;土工袋的稳定不仅与充填率有关,还受土工袋长宽比设计的影响,较大的长宽比不利于土工袋的稳定,且顺水流、垂直水流放置时稳定能力差别很大;实际工程中可在护底处土工袋下方铺设土工布,一方面可提高土工袋的摩擦稳定能力,另一方面也可起到一定的反滤作用。

[Objective]In order to explore the stability law of single geotechnical bag at the bottom of river bank revetment under the action of water erosion,[Methods]Based on the actual project of Tarim River geotechnical bag revetment,the flume model test platform was built,and the geobag models of different specifications were made.The deficiency of Robin volume formula in practical engineering application is discussed.Based on the test result of geobag,the response rules of key factors and stability in practical engineering,such as filling rate,ratio of length to width,roughness of underlying cushion surface,placement form and so on,are analyzed.[Results]The test result show that the thrust(FD)of the geotextile bag increases gradually with the increase of the filling rate,and the lift(FL)increases first and then decreases with the increase of the filling rate.When the aspect ratio is greater than 2.33,the stability of the geotextile bag decreases gradually when it is placed along the water flow,while the stability of the geotextile bag decreases with the increase of the aspect ratio when it is placed perpendicular to the water flow.The stability of the geobag is effectively improved by changing the roughness of the geotechnical bag and the underlying surface.[Conclusion]The result show that the filling rate directly affects the effective stress area of the geobag after filling,and then affects the size of FD and FL that make the geobag unstable.The stability of the geobag is not only related to the filling rate,but also affected by the design of the length-width ratio of the geobag.The larger length-width ratio is not conducive to the stability of the geotechnical bag,and the stability ability is very different when the downstream flow and the vertical flow are placed.In practical engineering,geotextiles can be laid under the geobags at the bottom of the protective bottom.On the one hand,it can improve the friction stability of the geobags,and on the other hand,it can also play a certain role in anti-filtration.