Research On Stability Evaluation And Treatment Of Ground Collapse At The K73+200～K73+500　Section Of Changping Highway

With the rapid growth of the economy in china,on one hand, a large number of highways and railways are being constructed all over the country caused by the demand of transportation has shaply increase,on the other hand,the mining scale of the metal and coal mine hasgradually increase caused by the growth of the demand of energy sources.Based on the above reasons, the geologic engineering problem of the gob of the coal mine would be fallen across inevitably. We inherit the economic loss caused by geological disasters which bring us the problem of instability and damage of subgrade and pavement when the finishedstope sink.This paper supported by the research project -'research on stability evaluation and treatment of ground collapse at the k73+200-k73+500 section of Changping highway' According to the investigation and measurement of Jilin province highway design institute,we found a ground collapse happened at the k73+200-k73+500 section of Changping highway.This section located in the border of Liufangzi coal goaf which lies in Gongzhuling city of Jilin procince.There has been no subsidence happened on the highway during the 12 years.April4,2009,monitoring results showed that the road surface elevation has sinked 1.1m. On May23,2009,monitoring results showed that the total surface subsidence has reached to 1.5m.The subsidence of road surface is too large to directly affect the security of Changping highway.The paper provide the survey methods of mined-out area,and make the further investigation for the size and features of the ground collapse based on the combination of drilling and geophysical exploration. Through the subsidence curve analysis of mined-out area,the characteristic and the trend of groud subsidence was got.The probability integral method was used to analyze the collapse development tendency.According to the road collapse data,a new method based on empirical mode decomposition(EMD) and weighted least squares support vector machines(WLS-SVM) has been put forward to forecast the ground subsidence. Finally the recovery treatment of highway through mined-out area was put forward. The study of this subject is of great significance to the similar engineering geological problem and engineering treatment.The main research results were as follows:1.The engineering geological conditions,the basic characteristics and scale of collapse were found out. The formation conditions and processes, influencing factors and failure modes of collapse were deeply analyzed.2.According to the charateristic of the road collapse data,surface movement is at the decline stage currently.There are two characteristics of this stage,the rate ground of subsidence is small and the ground movement trend to be stable.After June 28,2009,the surface subsidence of Changping highway increase slowly,the average setting velocity was 0.032cm/month. the setting curve has tend to smooth and the ground deformation has remained stable.3.The maximum subsidence of the Changping highway k73+288 calculated by the probability integral method is 129.2cm.The current actual measurement is 43.4cm more than the calculated value.the current measurement of the maximum subsidence is 172.36cm.Ttough speculation its reasons might be:â‘ there is a small circle mined-out area of group C coal seam under the k73+288 section,which would lead to a small range of caving;â‘¡it is the result of amplification of the F fault.At the present the mining inflence range on the right side of the Changping highway is 143m far from the road centerline.4. The empirical mode decomposition (EMD) and weighted least squares support vector machines (WLS-SVM) has been applied into the coal-mining-induced collapse prediction of a22 which is the biggest monitoring point. Three steps has been adopted to deal with the measured collapse data of a22 monitoring point:firstly, gain the smooth signal curve by cubic spline interpolation method; secondly, use EMD to deal with the time-space filtering and noise reduction to obtain the residual component which shows the collapse trend,the maximum relative error of measured data and calculated data is 0.87%; thirdly, input the dealt data to WLS-SVM model and then get the result of collapse prediction. The final collapse value has been predicted to be 174.34 cm,the average deviation of the final collapse prediction results using WLS-SVM is about 1.06%.5.For the settling section of k73+100-k73+420,the surface deformation has been remained stable according to the deformation curve if mining to keep in lane and mined-out area to maintain in statu quo.6. According to principles of technical feasibility and economic rationality, treatment of mined-out area collapse was carried out.Slip casting method is applied to the regulation project.The treatment width on both sides of the road is 263.65m,the treatment depth is 236m,and the treatment length along the road is 700m.