Analysis Of Damage Characteristics Of Building Wall Under Ground Fissure Activity In Longyao,Hebei Province

The development of ground fissures in Longyao of Hebei Province,has caused serious damage to buildings across ground fissures,and has endangered the daily production and life of local residents.Therefore,it is of great significance to explore the deformation and damage characteristics of the overburden buildings under the active ground fissures environment for disaster control and disaster prevention in the construction of buildings.On the basis of previous research results and combined with further field investigation,this paper analyzed the damage forms,characteristics and mechanism of Longyao ground fissures to buildings,generalized the damage mode of buildings across ground fissures in the area,summarized the main influencing factors of ground fissures to buildings,and combined with numerical simulation,explored the wall deformation when ground fissures obliquely crossed buildings.Failure response and crack resistance of superstructure under different foundation forms.The main conclusions are as follows:1.The surface extension length of Longyao ground fissure zone has extended to 35 km,which can be divided into three sections according to the outcrop and strike.Among them,the western segment is about 11.5 km in length,and the whole is nearly continuous in East-West direction,and has the characteristics of left-lateral strike-slip.The maximum width of ground fissures on the surface is about 20 cm,the maximum vertical offset is about 30 cm,and the maximum left-lateral strike-slip displacement is 10 cm.The middle section is divided into two ground fissures,the north one is about 1.2 km long,the north one is about 80 degrees long,the south one is about 11.8 km long,the direction is about 60 degrees north-east from nearly eastwest,the maximum width of ground fissures on the surface is about 15 cm,the maximum vertical offset is about 20 cm,and the maximum is about 20 cm.The left-lateral strike-slip displacement is up to 8 cm,and the east section is about 11.5 km in length,which is distributed intermittently along the north-east direction of 60 degrees,and has the movement characteristics of positive and right-lateral strike-slip.The maximum crack width of ground fissures is about 30 cm,the vertical dislocation is not obvious,and the maximum strike-slip displacement is up to 6 cm.On the section,the groove reveals that the ground fissures have the characteristics of "multi-branching and multi-stage" and have the attributes of synsedimentary fracture activity,which reflects that the fault activity,sedimentation and fracture activity have a unified tectonic background and are controlled by the unified tectonic stress field.2.The activity characteristics of Longyao ground fissures are obviously segmented.Generally speaking,the activity of the western segment is the strongest,followed by the middle segment and the eastern segment.Among them,the vertical dislocation rate is about 4.5 cm/a,the horizontal tension rate is about 1.2 cm/a,the left-lateral strike-slip rate is about 0.6 cm/a;the vertical dislocation rate is about 3.5 cm/a,the horizontal tension rate is about 0.9 cm/a and the left-lateral strike-slip rate is about 0.5 cm/a in the middle section;the activity of the eastern section is weak and intermittent,and only occasionally a series of beaded collapse pits can be seen,which makes it difficult to calculate its activity rate.In addition,the ground fissures have typical "three-direction" movement characteristics.Among them,the vertical displacement is the largest,the horizontal tension is the second,and the horizontal torsion is the weakest.The ratio of the three is about 1:0.26:0.15.3.Under the influence of the "three-way" movement of ground fissures,the wall of the superstructure spanning the fissures is mainly subjected to the combined force of "bending,shearing and torsion",which causes different forms of cracking and "warping" deformation of the building.4.The main influence factors of ground fissure active zone on building damage characteristics include: the mode and intensity of ground fissure activity,the influence range of ground fissure zone,the physical and mechanical properties of rock and soil in the zone,and the intersection relationship between buildings and ground fissures.Among them,the mode and intensity of ground fissures are the main factors causing the destruction of buildings;the influence scope of the fissure zone is an important factor for the destruction degree of buildings;the physical and mechanical properties of soil in the fissure zone are the factors that aggravate the destruction of buildings;the intersection relationship between the positions of ground fissures is a direct factor affecting the destruction form of buildings.5.The numerical simulation results show that when Longyao ground fissure passes through the building foundation,the deformation and failure of the wall begins at the intersection of the wall and the lower fissure,and propagates progressively upward in the form of inclined fissure,which tends to be opposite to the tendency of the fissure.Generally speaking,when local cracks pass through the house,there are obvious differences in the damage modes and scope of the front and rear walls of the house.Compared with the deformation and failure of the front wall,the back wall shows a certain lag.With the increase of the intersection angle between the direction of crack and the building,the lag effect gradually weakens.In addition,besides the obvious deformation and failure of the main wall(front and rear walls),the corresponding plastic strain zone appears at the toe of the side wall,and the plastic zone of the side wall decreases gradually with the increase of the direction of cracks and the angle of intersection between the building and the side wall.Compared with raft foundation,the damage of strip foundation is more serious,so it is more reasonable to use raft foundation for buildings across ground fissures.