Study On Panzhihua Airport Landslide Stability By Considering Acid Rain

Due to the rapid development of modern industrial technology since the Reform and Opening-up,China has become one of the three major regions(together with Europe and America)of acid rain in the world.In recent years,some scholars found that the occurrence of landslides may be spurred by acid rain.To better evaluate landslide stability and design supporting structures,the effect of acid rain on landslide needs to be revealed.In this thesis,we took the airport landslide in Panzhihua city of typical acid rain area as an example,and proposed a hypothesis about the occurrence mechanism of the landslide:the serious acid rain pollution in Panzhihua City may aggravate the slaking of mudstone at weak interlayer,eventually provide favorable conditions for the occurrence of the landslide.Then,we studied the influence of acid rain with different pH on the slaking characteristics and its mechanism,by carrying out the field investigation,laboratory test and theoretical analysis.Next,Particle Flow Code 2D was adopted to simulate the landslide under different pH conditions.Through comparing the deformation characteristics of the landslide under different pH condition,the influence of acid rain on the stability of the landslide was revealed.Conclusions of this thesis were as follows:(1)The mudstone at weak interlayer was selected and processed as rock samples.Then a series of slaking experiments were comparatively carried out under different pH conditions.Based on the fractal theory,the fractal dimension was introduced into quantitatively describing the slaking characteristics of mudstone.The results showed that the fractal theory could better reflect the acid rain slaking characteristics of silty mudstone,and the higher the fractal dimension is,the higher the slaking degree.The logarithmic positive correlation exists between the fractal dimension and the duration of acid rain,the final fractal dimension and the acidity of rainfall.(2)In order to explore the micro-mechanism of acid rain aggravating the slaking behavior of silty mudstone,we adopted a series of analytical methods,including analyzing cation compositions changes in different pH slaking fluid,observing micro-structure change of samples before and after acid rain treatment as well as analyzing slaking failure modes of silty mudstone.The results highlight that the slaking of mudstone at weak interlayer can be aggravated by acid rain reacting with dolomite and calcite.The lower the pH of acid rain is,the greater the dissolution degree of dolomite and calcite is,the worse the integrity of mudstone is,the more potential slaking paths are,and the higher the slaking degree is.With the decrease of pH value of acid rain,the slaking mode of mudstone gradually develops from surface peeling to simple splitting,secondary splitting and transverse splitting.(3)Through comparing the cations in acid rain and output spring water,we found that there was a dramatic increase in Ca²⁺,Mg²⁺from acid rain to output spring water.Such increase proved that the slaking of mudstone at weak interlayer actually occurred in acidic condition and was accompanied by the dissolution of dolomite and calcite.Thus we deemed that the serious acid pollution did influence the slaking of mudstone at weak interlayer and eventually prompt the occurrence of the Panzhihua airport landslide.(4)Based on the fractal dimension of mudstone under different pH conditions,the strength parameters of mudstone at weak interlayer under the action of acid rain with different pH were theoretically determined.In addition,the strength parameters of fill body and sandstone under natural condition were adopted.Then,the biaxial compression simulation test was carried out to acquire the meso parameters.Next,a series of discrete element model of Panzhihua airport landslide under different pH condition were established.Through comparing the difference of deformation characteristics,the influence of acid rain on landslide stability was quantitatively described.The results showed the process that acid rain aggravate the slaking of mudstone at weak interlayer could affect the deformation characteristics of the landslide,increasing the speed value and displacement value.The displacement value of the monitoring points ID1,2 and 3 at the slope top,slope center and slope foot was 53.8m,67.6m and 33.8m under pH=7 condition,respectively.With the decrease of pH,the displacement value of ID1,2 and 3 increased to 63.6m,72.2m and 42.3m under pH=5 condition,and were up to 65.0m,75.2m and 49.1m under pH=3 condition.Such results meant that with the increase of rainfall acidity,the instability of airport landslides is further promoted.In a nutshell,the stronger the acid rain effect,the lower the stability of airport landslides.