| The medium-high liquid limit clay formed by the yellow deposits in the lower reaches of the Yellow River is a kind of unique soil in China.It is mainly distributed in the northwest southwest and of the alluvial plain of Shandong Province.The special historical causes make the soil mainly composed of powder and clay particles with high content and high grinding roundness.It is easy to absorb water and has a high natural moisture content,strong water retention,large plastic index and other characteristics.Due to poor road performance,it is not appropriate to directly fill in roadbeds as required by the regulations.At present,the method of replacing or modifying this type of soil in subgrade of expressway is often used.But the construction efficiency is relatively slow and the construction cost is relatively high,resulting in a large amount of digging soil and wasting of land resources.However,in actual projects,there are often cases where the clay subgrade under high water content and low compaction degree is in a stable working condition with a high moisture content and a low degree of compaction.Can the compaction degree control standards be relaxed under each water content according to the special causes of the high liquid limit clays of the Yellow River in Shandong?After completion,the compaction degree of the medium-high liquid limit clay subgrade in the floodplain remains basically unchanged.What is the influence law of the water content changing with the season and time affecting the strength index?How should taking these factors into consideration,and making further refinement of the existing standard rolling control standards?In addition,due to the current soaring prices of clay-modified materials that cannot be applied to directly filling in roadbeds.It is necessary to find a more efficient and economically modified alternative material to promote the process of subgrade filling of high liquid limit clay in the Yellow River flood are.Therefore,accurately revealing the static and dynamic behavior under different physical conditions of middle and high liquid limit clays in the Yellow River,and proposing the subgrade filling and modification techniques of corresponding direct control standards under high water content are problems that need to be solved in construction.Based on the above issues,under different physical conditions,this paper systematically studied the static and dynamic strength characteristics of medium and high liquid limit clays in yellow flooded areas,including CBR strength,shear strength,dynamic and static rebound modulus,and their correlations.In addition,this paper put forward corresponding control standards for filling according to the strength standards in relevant design codes.The main conclusions of this paper are as follows:(1)Based on the requirements of CBR strength and modulus of resilience in the specification,the control indexes and control standards for subgrade filling after direct filling and modification were given;(2)The soil-water characteristic curve(SWCC)of medium and high liquid limit clays in the yellow pan area was obtained under different compaction degrees,and the two-factor experience of the shear strength index,moisture content,and compaction degree of medium and high liquid limit clays in the yellow pan area was established.Based on the relationship,the method for determining the equilibrium moisture content of medium-high liquid limit clay in the Huang-fan area and its corresponding shear strength index were proposed;(3)The static and dynamic engineering characteristics database of mid-high liquid limit clay in Yellow River Flooding Area of Shandong Province was established,and a dynamic rebound modulus prediction model was proposed;(4)A new modified material suitable for middle and high liquid limit clays in the Yellow River Flooding Area under higher water content was proposed,and related modification processes were optimized.The research results of this paper can be directly applied to guide engineering practice and have significant social and economic benefits. |
