| Ground fissure is a kind of geological disaster with concealment and slow change,which has caused direct damage to many types of engineering construction projects,such as linear engineering projects,water conservancy facilities and urban buildings,and has a great threat to human life and property safety.Therefore,it is urgent to monitor the ground fissure disaster effectively,analyze its activity and predict its displacement trend,so as to provide a strong judgment basis for the prevention and control of the ground fissure disaster.The displacement activity of ground fissures is an important reference index to evaluate the activity of ground fissures.It has become the main goal of this research direction to obtain the deformation variables of ground fissures accurately,comprehensively and in real time.The shape accel array(SAA)has the characteristics of high accuracy and high frequency,so it can be used in deformation monitoring project.Its data acquisition accuracy can reach ± 1.5mm/32 m,and the frequency can reach one hour.Therefore,in this research,SAA is embedded in Xiwang Road ground fissure,running through the hanging wall and footwall of the ground fissure,and real-time acquisition of three-dimensional displacement information in the ground fissure.However,it is not reliable to evaluate the activity of ground fissures only from the change of displacement activity,and the displacement variation can not reflect the effect of the interaction between the mechanism of ground fissures and the external forces of the environment.Therefore,this paper provides a systematic method to deal with SAA monitoring data.On this basis,an analysis method of the activity of ground fissures based on the instantaneous total energy model is proposed.Displacement activity analysis and instantaneous total energy analysis are complementary to each other,which makes up for the defect of single analysis method.Because the occurrence of ground fissure disaster is very sporadic,there are many influencing factors and the influencing factors are often random.Therefore,only displacement monitoring and activity analysis is not enough to avoid the risk of ground fissure disaster.We also need to carry out safety assessment in advance,so it is necessary to predict the displacement activity of ground fissure.Based on the above methods and objectives,the main contents and research results of this paper are as follows:(1)Design of Xiwang Road ground fissure monitoring scheme.The traditional monitoring methods of ground fissures and SAA monitoring technology used in this paper are introduced in detail.The advantages and disadvantages of traditional monitoring methods and SAA monitoring technology are compared and analyzed.Through rationalization and optimization of SAA's underground layout plan,16 segments SAA sensors are arranged horizontally and 8 segments SAA sensors are arranged vertically to obtain the three-dimensional deformation information of monitoring point of Xiwang Road ground fissure from November 23,2015 to March 2,2017.The experimental results show that SAA technology is an effective method to monitor the internal displacement of ground fissures,and the high sampling frequency data obtained can be used to describe the activity model of ground fissures in detail.(2)The periodic deformation law of Xiwang Road ground fissure.In this paper,the periodic deformation law of Xiwang Road ground fissure,Beijing,is summarized from two aspects of the ground fissure surface and underground,based on the results of leveling,global positioning system and SAA sensor.Combined with the previous research,this paper analyzes and discusses the causes of formation and development of Xiwang Road ground fissure.The damage caused by Xiwang Road ground fissure can be avoided to a certain extent by reasonable design.(3)The integrated signal decomposition and Spearman correlation coefficient to reduce the noise of SAA sensor monitoring signal.For the displacement signals of ground fissure monitored by SAA,the Extreme-point symmetric mode decomposition is used to decompose the into several simple sub signals.Then,the correlation between the sub signals and the original signals are solved by using the Spearman correlation coefficient,and the sub signal dominated by noise will be eliminated,so as to achieve the purpose of combined de-noising.The root mean square error and signal-noise ratio are used to evaluate the accuracy,and they both are increased by about 10%,so the denoised results are satisfactory.(4)An analysis method of ground fissure activity based on instantaneous total energy model.Because the previous energy model is unchangeable by default when it is solved,it is simply projected to some fixed frequency points,this method is not desirable.Therefore,this paper puts forward the instantaneous total energy model based on the superposition of the relative kinetic energy of the sub signals,which not only expresses the characteristics of the energy changing with time,but also gives the actual physical significance of the instantaneous total energy.The relative kinetic energy model is used to calculate the instantaneous energy of each sub signals displacement changing with time,and then the instantaneous energy of sub signals are superposed to obtain the instantaneous total energy.The change of the instantaneous total energy is used to reflect the activity of ground fissure.(5)Prediction of ground fissure displacement based on support vector regression.The SAA sensor buried in the ground can measure the displacement change of the monitoring point once an hour,and the sampling frequency of the data can meet the requirement that we can monitor the deformation activity of the ground fissure almost in real time.However,the occurrence of ground fissure disaster is always slow and random.Therefore,we can use support vector regression method to predict the daily displacement change of SAA monitoring at the same time of real-time monitoring,so as to predict and evaluate the potential risk of ground fissure disaster. |
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