Study On Influence Of Frost Heaving Effect On Retaining And Protection For Excavations Of Soil Nailing Wall In Seasonal Frozen Zone

The foundation pit engineering in the seasonal frozen area needs to consider the influence of soil frost heave during wintering.The soil nailing wall support is widely used in foundation pit support engineering.The frost heaving of the soil often causes the surface layer of the soil nailing support structure to fall off,and the soil nail is pulled or pulled out.In serious cases,the foundation pit collapse accident may occur.In this paper,the foundation pit soil nailing wall support is taken as the research object.Based on FLAC3 D numerical simulation software,the influence of frost heave on the foundation pit support of soil nailing wall is analyzed,and the corresponding frost heave prevention measures are given.The main research results are as follows:First,The domestic and international research status of the soil and frost heaving mechanism in the seasonal frozen area is summarized in detail,and the research status of the effect of domestic frost heaving on the foundation pit engineering is comprehensively discussed.Second,Through the existing research results,the frost heaving process and formation mechanism of the soil are expounded,and the resulting frost heave force and its influencing factors are summarized and analyzed.Third,The types and influencing factors of the frost heaving damage of the soil nailing wall are analyzed,and the corresponding frost heaving measures are given on this basis.Fourth,based on the numerical simulation software analysis results,under the effect of frost heaving,(1)the axial force of the soil nail increases obviously,and the axial force of the soil nail head increases particularly.(2)The axial force of the soil nail is divided into the small nucleus type distribution on the two sides of the middle when the excavation is completed.It becomes the pin-shaped distribution with the largest axial force of the soil nail head and gradually decreasing along the length of the soil nail.(3)The horizontal displacement of the soil increases significantly.(4)The lower the temperature,the greater the axial force of the soil nail,and the one-way distribution mode in which the nail head is gradually reduced along the length of the soil nail.The maximum horizontal displacement of the soil appears at the top of the slope.Under different negative temperatures,the horizontal displacement of the slope top and the freezing temperature are linear.(5)The soil type is different,the horizontal displacement distribution after frost heaving is different,the horizontal displacement of coarse sand is firstly reduced,and then the approximation remains stable,while the silt,clay and silty clay are decreasing.-Increased-decreased S-type distribution law.(6)The greater the soil density,the greater the axial force of the soil nail,and the horizontal displacement of the soil is correspondingly increased.After fitting,it is found that there is a logarithmic relationship between the soil density and the maximum axial force of the soil nail,which is linear with the horizontal displacement of the slope top.(7)The axial force of the soil nail increases with the increase of water content.After fitting,it is found that there is a quadratic function relationship between the water content and the maximum axial force of the soil nail,and a power function relationship with the horizontal displacement of the slope top.(8)With the increase of the thickness of the soil nailing wall surface,the horizontal displacement of the slope top is continuously reduced,and the axial force of the soil nail is increased.