Research On The Treatment Technology Of The Damage Of The Foundation Of Transmission Line With Collapsible Loess

Collapsible loess is widely distributed in China,especially in the northwest.The characteristics of loess arc most typical.It is characterized by complete formation,good development,thick stratum and obvious collapsibility.For example,the thickness of the loess in Gansu and western Yunnan is widely distributed.The self-weight collapsible loess has a high level of collapsibility,mostly grade Ⅲ and grade Ⅳ,which poses a great threat to the foundation of the substation in the collapsible loess area of Gansu.In order to eliminate the loess collapsing effect,the technical treatment of destroying the undisturbed loess structure is often adopted in the foundation treatment of the large-thickness collapsible loess transmission tower.The large thickness of the lime soil or the Sanqi lime soil is laid to eliminate the collapsible deformation of the loess,but this treatment When the thickness is large,the construction is complicated and the construction cost is high.Aiming at the problems and defects in the above-mentioned collapsible loess foundation treatment method,this paper proposes a new technology for treating the collapsible loess foundation of the transmission line tower the composite foundation of lime soil cushion and anti-seepage membrane,the method is numerically calculated.On the basis of the optimization,the thickness of the Erbai lime soil or the Sanqi lime soil was optimized,and the guiding value of the thickness of the lime soil cushion under the foundation of the power transmission tower was proposed.At the same time,the anti-seepage membrane was set up,which played a good water blocking effect from the source.Eliminate the collapsing of loess,and provide theoretical reference and technical support for the design of transmission tower foundation engineering in the collapsible loess area of Gansu.The specific research content involved is as follows:1.To summarize and analyze the distribution,genesis and collapsibility mechanism of collapsible loess,and to study the history and current status of collapsible loess at home and abroad,the calculation method of loess wetting deformation and the collapsible loess foundation treatment method.Combined with the 750kV Guanting-Lanzhou East Ⅱ power transmission project,a typical soil sample was taken to take the soil samples,and the soil samples were subjected to indoor compression test,collapsibility test and triaxial test.The test results were analyzed in the northwest region.The loess parameters of the collapsible site passing through the transmission proj ect have been deeply understood and mastered.2、Through the on-site in-situ immersion test,the settlement measurement of the ground settlement observation point and the deep settlement observation point is carried out,and the variation curve of the settlement amount and the settlement rate of the corresponding position inside and outside the immersion pit during the monitoring period are obtained.At the same time,the numerical simulation is used.The method reproduces the sedimentation and water seepage process during the test immersion process,and verifies the reliability of numerical simulantion.3、Analysis and Research on Engineering Design Data of Guanian Line,According to the original type of undisturbed soil excavation foundation and inclined column excavation used in the proj ect,four collapsible loess treatment schemes were designed as research schemes.In the process of rainfall or irrigation infiltration,the characteristics of foundation humidification deformation of different schemes were studied,and the advantages and disadvantages of each scheme were discussed.At the same time,the original treatment scheme of adding waterproof layer to the inclined column excavation foundation was optimized.The thickness of the cushion was optimized by numerical simulation method,and the treatment effect of the Erba lime soil and the Sanqi lime soil cushion was compared and analyzed.The measures for the specified thickness of the lime soil are completely feasible.4、Organizing and analyzing the characteristics and functions of artificial geotextiles,as well as their application in underground irrigation and drainage systems,roads,railways,retaining walls,bank slopes and soil protection.Combined with the characteristics of power transmission engineering,the scheme of applying waterproof geotextile to the treatment of collapsible loess site is proposed.5、From the engineering practice,it demonstrates that the 28th lime soil has the advantages of economical convenience,simple construction and remarkable effect in the treatment of the wettlement site of the transmission line in the northwest region,and the construction technology of the lime soil in the transmission line proj ect is given.From the aspects of waterproofing and basic design schemes,the basic selection of collapsible loess area,all-round long and short legs and unequal height foundation design,ecological vegetation slope protection,spoil disposal and enhanced drainage measures were studied.