Analysis of Typical Building Collapse and Rescue Characteristics after Earthquake

Summary

The collapse of buildings after the earthquake caused people to bury their pressure. Rapid search and rescue are one of the important ways to effectively reduce casualties. In this paper, by studying the collapse type of typical buildings after the earthquake, from the perspective of vertical and horizontal damage of buildings, a three-level classification system is proposed, and the stress and living space of each type of collapsed buildings are discussed. At the same time, a large number of documents and Wenchuan Earthquake rescue case data are used to analyze and summarize the technical characteristics of route selection, rescue channel establishment, and rescue of trapped persons during rescue operations for various types of buildings.

Keywords

Type earthquake building collapse rescue

introduction

Although the earthquake is a small probability event, its release of energy is huge. The destructive earthquake can cause the surface decoration, internal space, and even the building structure of the surface buildings (structures) to change, resulting in cracks, spalling, tilting, and even collapse. . In particular, the devastating earthquakes that occurred in cities, economically developed areas, or densely populated areas of populations not only pose a threat to the life and property of the people, but also cause serious damage to economic and social development.

According to the classification of the destruction level of buildings at the earthquake site (National Standard of the People's Republic of China, 2012 ), basically intact, slightly damaged, and some moderately damaged buildings, although with varying degrees of damage, the main structure was not destroyed, causing The damage is limited, and buildings that have severely damaged and destroyed grades are completely deprived of their functions, forming partial or overall tilt or collapse. The collapse of buildings after the earthquake was the main reason for the burial pressure of people, and there was also a certain relationship between the area of ​​damaged buildings and casualties (Wu Xinyan et al., 2014 ). More than 90% of the casualties in the Wenchuan earthquake were caused by the collapse of buildings, and thus they collapsed. Buildings are the focus and difficulty of search and rescue work. The process of rescue in different types of collapsed buildings is extremely complicated. There are also differences in the search and positioning of burying personnel, the formulation of rescue plans, and rescue methods and techniques. In particular, some deep burial pressures generally cover more than 6 hours. Even for more than 24 hours, this is a great test for the survival rate of buried personnel. Through the classification of buildings collapsed, the characteristics and laws of living space can be grasped, which can provide a basis for the identification of location of people's buried pressure. At the same time, through case studies, different types of rescue technical points can be summarized in a timely manner, which can effectively shorten rescue time and improve rescue efficiency.

1 Survey of domestic and foreign

1.1 Types of Building Collapse and Living Space

Foreign research on the classification of collapsed buildings after the earthquake was studied earlier. The Public Security and Emergency Preparedness Division of Canada has collapsed buildings into V -shaped, inclined-supported, and sandwiched ( OCIPEP , 2002 ); the U.S. Fire Protection Association has collapsed buildings into ramps , V -shaped, cantilevered, and pie-shaped. A type 1; international Search and rescue Advisory group (international Search and RescueAdvisory group) based on the survival of the building collapsed into shelving, cantilever type, pie-type, V-type and A-type.

China began research in the early 21st century by drawing lessons from foreign relevant achievements. Gu Jianhua ( 2003a ) divided buildings into inclined support type, cantilever type, V type, and sandwich type according to collapsed space , and then subdivided into floor leaning type and oblique type. Relying on the cantilever type, V -type, collapse type, turning type and compound type (Gu Jianhua, 2003b ); Guo Hongmei ( 2008 ) collapsed buildings into inclined support type, cantilever type, V type, sandwich type, flip type, and composite type; According to Zhao Guocun et al. ( 2010 ), according to the depth and location of the living space in the rubble, the buildings are divided into partial wall collapses, most collapsed walls, collapsed floors, cantilevered beams, and V -shaped collapses. The stacked collapse type; Weng Xuran ( 2015 ) divided the collapsed mode into complete collapsed, weak collapsed, and partially collapsed depending on the collapse of buildings and rescue methods; Dong Ning ( 2016 ) divided the collapsed approach into a sandwich type, V type and monoclinic type. Some scholars classified the collapse into 8 categories according to the factors that caused the collapse of the building : prone, cantilever, V , pancake, curtain fall, chain reaction, inward / outward and 90 degree; The characteristics of the rescue work included the collapse of the building into slanting, collapse, collapse and V- shaped collapse. Some scholars discussed the type of local living space of collapsed buildings: Chen Weifeng et al ( 2008 ) divided the collapsed space of buildings into inclined support type, cantilever type, V type and sandwich type; Pu Maomin ( 2008 ) buried deep pressure in Wenchuan Earthquake. The space is divided into an overall collapse irregular type, sandwich type, delta type and V shape; Zhang Guangjun ( 2009 ) divides the collapsed space into monoclinic, V- shaped , multi-layer sandwiched and irregular; Li Yigang et al. ( 2010 ) Divided the collapsed building space into V -shaped, cantilevered, inclined-supported, sandwiched, and composite types.

1.2 Relief technology for burying personnel

Buried personnel rescue is the core task of emergency rescue after the earthquake. At present, the development of the emergency rescue field and the frequent occurrence of large catastrophic earthquakes have prompted the construction of domestic earthquake professional rescue teams to grow in size, and rescue techniques have been continuously practiced and innovated. In recent years, some domestic research activities have also been carried out, mainly including rescue programs and strategies, rescue site organization and management, and rescue operations.

In respect of rescue plans and strategies, Ding Xiankong ( 2008 ) summed up the five basic processes for excavating and breaking , namely, demarcating the scope of excavation and breaking, opening up rescue tunnels, selecting equipment and equipment, digging life-saving tunnels, and digging for demolition. Etc.; Fan Maokui et al. ( 2009 ) divided the rescue of trapped people into five major areas, namely personnel positioning, psychological comfort, life supply, excavation channels, and security; Zhao Guocun et al. ( 2010 ) summarized the on-site search and rescue strategy, ie information collection and evaluation. Rescue of the surface of the rubble, search and rescue of personnel in key living spaces, and rescue and support in the rescue process; Song Shuyi ( 2015 ) proposed five levels of rescue programs , namely the selection of rescue passages and emergency evacuation routes, structural stability assessment and reinforcement , rescue equipment and methods of rescue, medical rescue and accident response; Dong Ning ( 2016 ) combined the depth of personnel trapped summed up the implementation of the rescue of several major aspects: First, rapid assessment, and second, shallow search and rescue, the third is Middle-level dog rescue, fourth, deep instrument positioning rescue, and fifth, reasonable support.

In the field organization and management of rescue operations, Yang Jianmin et al. ( 2004 ) proposed the rescue procedures, measures, and points for organization and command of the earthquake scene; Ma Zhanquan ( 2008 ) thought that the characteristics of the operations of the fire brigade in carrying out the earthquake rescue included the dispatch of the incoming police, the rapid arrival, and the arrival of command personnel. , organizing logistical support and coordinating rescue operations; Zhang Guangjun ( 2009 ) proposed four disposal procedures for an earthquake collapsed building accident , that is, the mobilization of personnel equipment, the establishment of an on-site temporary command post, information collection, alerting, and evacuation of personnel, sources of danger Control and elimination; He Weicheng ( 2014 ) divided the rescue operations into three major parts to manage, which mainly included the use of professional rescue knowledge and skills, the safety control at the rescue site, and various auxiliary support on the site.

In practical operation of the technical aspects of rescue, Bi Xingquan (2008) summarizes the clear burying matter, burrows dug wells, opening oxygen, psychological comfort and other four rescue techniques; Pumao Min (2008) discussed the rescue method within the living space of deep staff, That is, the layer-by-layer cleaning method, the digging channel method, and the comprehensive method; Ma Zhanquan ( 2008 ) proposed the rescue of the four steps, namely, transport air, reaming drilling joints, hole joints and tunneling excavation; Zhou Xueang et al ( 2009 ) introduced the current Six kinds of commonly used rescue techniques, namely hole digging, protection and fixation, mechanical lifting, life support, medical rescue, and psychological relief; Zheng Chunsheng ( 2010 ) proposed 10 practical technologies for the protection and rescue , namely search and rescue positioning, safety support, Digging, digging shoveling, shaft excavation, air cushion support, rubble removal, rope rescue, scientific feeding, and casualty removal; Wang Cuiliang ( 2011 ) proposed four major aspects of the rescue, including search and rescue positioning, safety support, and rubble. Removal, air-cushioned support; He Weicheng ( 2014 ) combed six rescue methods, including reaming, hole digging, protective fixing, and mechanical assistance. Help, life support, and psychological comfort; Song Gongru ( 2016 ) discusses the application of life exploration, telemedicine, robotics, industrial endoscopy, and remote sensing technology in rescue operations. At the same time, some scholars also explained the rescue technology through earthquake catastrophic rescue cases, especially the Beichuan county located in the XI-degree zone in the extreme earthquake zone during the Wenchuan earthquake. More than 90% of buildings and structures were severely destroyed or collapsed (Li Xiaojun et al., 2008 ). carry out case studies and summary provides a number of basic data, such as Deng Min-xian (2008) summed up the rescue process earthquake Qushanzhen kindergarten and Beichuan County Department of Transportation two bury personnel, emphasizing a method to open up the rescue channel and support protection, and Key technologies for rescue in seriously collapsed buildings; Wu Tiesheng ( 2010 ) summarized the rescue process of the Beichuan Middle School, Qushan Primary School, and Beichuan Middle School during the Wenchuan earthquake and discussed key technical links; Feng Zhize ( 2013 ) focused on damage and personnel distribution. structural safety assessment, rescue program development, and implementation of the rescue should pay attention to the problem, summed up earthquake relief in three cases, with emphasis on the technical characteristics of relief in the fully collapsed buildings or small spaces.

2 Earthquake-induced collapse of buildings

Literally understanding the collapse of a building should include the phenomenon of "falling" and "collapse". If one is missing, it does not conform to the actual situation at the site of the earthquake. Most of the existing classification studies focus their analysis on the vertical collapse of the building and classify it in combination with the collapsed living space structure, such as V -shaped, A -shaped and cake-shaped, but horizontally on the building. The phenomenon of dumping and tilting is of little concern. In order to reflect the characteristics of collapsed structures, to show the degree of damage to buildings, and to distinguish the use of rescue methods and techniques, this paper, in conjunction with the composition of living space, subdivided the types of buildings collapsed, and collapsed buildings into slanted and collapsed buildings. Type, and composite type.

2.1 inclined type

Buildings are flipped by angles, and their length and width change less, ie no collapse occurs. Buildings are fractured due to failure of one side of load-bearing members such as vertical wall columns and foundations. They cannot support. They will fall forward or backward, form a certain inclination angle, or even be tiled on the ground at 90 degrees. . Or because of the seismic force, the building forms left and right slopes or tensile deformations, and the length of the sides shifts, and there is a certain angle with the vertical line. Tilt type can be divided into left and right tilt type and front and rear tilt type, each type includes partial tilt and overall tilt. Tilted buildings can easily affect surrounding buildings and form a chain reaction.

2.2 collapse type

Vertical displacement changes occur in buildings, and there are fewer parallel dislocations. Due to the foundation failure, the failure of a floor or a partial support, or the failure of a local support, the building experiences a partial or overall parallel decline and collapse, which can be divided into partial collapse and complete collapse. Local collapse can be divided into inclined type, V type, cantilever type and sandwich type according to different living space . The more common categories of collapse are V- shaped, A- shaped, and pie. Usually multi-storey buildings are easy to form slumps, including multi-storey masonry buildings with large business spaces and multi-window openings. The high-rise buildings of the RC structure are completely collapsed and there may be partial or partial collapse.

2.3 Compound type

There are two kinds of damage to the building: slope and collapse. The two may appear at the same time, or one of the damages may be too great, causing another new damage. If the building is tilted forwards and backwards, when the tilt angle is too large, it may be broken near the middle and bottom position, or the bottom may be squeezed and collapsed. Tilting buildings are prone to collapse due to unbalanced forces on the bottom layer, which can be accompanied by a certain degree of torsion.

3 Rescue techniques for burial personnel in typical collapsed buildings

3.1 The living space of collapsed buildings

The process of burying pressure in the earthquake is complex and changeable. It is not only related to the time of the earthquake, seismic energy, and the structure of the building, but also related to the layout of the interior of the house, decoration, and the location of the items, and even related to the activity process and habits of the people. Complex external and internal factors have led to extremely difficult search and rescue of trapped people after the earthquake. The classification of collapsed buildings based on living space not only provides a reference for ambulance personnel for on-site rescue, but also formulates scientific and effective rescue plans and methods for different living space structural characteristics and burying pressure locations (see Table 1 ). The rescue time will fundamentally improve the efficiency of the rescue.

3.2 The choice of rescue route

The rescue route of the collapsed building should be given priority in the formulation of the plan, and strictly follow the principles of safety, reasonableness and feasibility (Song Shuyi, 2015 ), and fully consider issues such as time cost, distance cost, technical difficulty, and operational safety.

3.2.1 Relief route for inclined buildings

Due to the high integrity of the inclined building, the angle of inclination is not large, and the rescue route can be selected by both external and internal rescue. External rescues generally use ropes from building roofs to reach trapped places, and use ropes or ladders to reach trapped places from the roofs of neighboring buildings or in appropriate locations, and then rescue personnel through broken doors and windows. Heavy rescue crane jibs or excavator work buckets can also be used to rescue trapped persons. Internal rescue can be implemented in the buildings from the bottom of the building, external corridors, or roof skylights.

3.2.2 Rescue route for collapsed buildings

The collapsed buildings are the top priority for relief. The surface and shallow layers have a low degree of buried pressure, and some parts of the body are exposed. The buried structure can be visually identified and the rescue route is relatively simple. The rescue route for the middle and deep layers of people is complicated, and combing Wenchuan Earthquake scene rescue cases, it is found that many vertical portraits are used longitudinally. Excavation, horizontal excavation, vertical well excavation, horizontal hole digging and other methods. Longitudinal excavation is suitable for serious or even complete collapse of buildings, low support gaps, deep burial of people, etc. The overall time-consuming, but relatively high safety, such as the Haiti earthquake in 2010 , the use of longitudinal excavation routes; horizontal excavation generally suitable for construction With multiple supports and multiple gaps, the rescue will take a short time, but it will easily damage the support and cause secondary collapse. The necessary support and reinforcement will be needed. Vertical and horizontal hole excavation and horizontal hole digging are mostly used for serious collapse of buildings. People are buried vertically and horizontally and are difficult to locate. The specific rescue route selection should be based on the collapse structure of the building and the location of the person burying pressure, as shown in Table 2 .

3.2.3 Rescue route for complex buildings

The composite building has two kinds of damages: tilting and collapse, and its structure is extremely unstable. Therefore, the horizontal excavation method is generally not used alone, and the vertical demolition and vertical well excavation are often used to enter the building. The earthquake Kitagawa mobile branch office five layers, resulting in seismic 1--2 layer laminated collapse, greatly inclined three or more layers. Open the channel longitudinally at a short distance and rescue it by means of lateral boring.

3.3 Rescue technical features

Rescue techniques for collapsed buildings mainly include demolition, cutting, support, ropes, jacking, handling, and traction. The entire process of the rescue program, that is, the selection of routes, the establishment of rescue channels, and the rescue of trapped persons, should be based on actual conditions. Choose the right operation.

3.3.1 Tilted buildings

Although slanted buildings do not collapse, the main body is inclined, the structure is damaged, and there is a risk of collapse. The safety assessment should be conducted by the structural experts, and the rescue should be carried out after supporting and protecting. Through a comprehensive analysis of building height, inclination angle, and force conditions, select suitable support points and support them with supports such as jacks, columns, and sleepers. You can also use trunks, door panels, coat racks, and collapsed houses. The wooden beams and columns and other portable equipment allow conditions to be supported by the crane boom. The methods of support mainly include temporary support, corner support, horizontal support, space support, T -support, and lateral support. It is generally adopted from the top of a building or adjacent buildings to carry out rescue operations, and to avoid increasing the degree of tilt and avoiding structural instability, it should be entered from the opposite direction of building inclination and support. After manual removal of the burying objects, according to the physical condition of the trapped persons, they may choose to send trapped persons to a safe area through a vertical lift or transfer system.

3.3.2 Collapsed buildings

For the collapsed buildings, a series of operations such as hole drilling, jacking, breaking and cutting, removal and transportation are commonly used to excavate the rescue tunnel and rescue the trapped persons. The safety can be ensured and the conditions permit. Equipment for rescue.

The main supporting point of the reclining type in the local collapse is the leaning wall, so the wall cannot be used as a working surface for any demolition work. Generally, the wall is drilled horizontally and inwardly from both sides leaning against the wall, or collapsed. The holes formed in the process are expanded and excavated. Before the excavation, the wood and lifting equipment are used for local support. After approaching trapped persons, manual tools or bare hands should be used . The key to the rescue of slanting buildings should be support and reinforcement. The function of the supporting columns should be emphasized, and the integrity of the supported components should be taken into account. It can also be supported by mechanical lifting. The V- shaped building has multiple supporting points in the force, and there are more triangular spaces ( middle and sides of the V character). When the burial pressure point is located inside the V character, the living space is located at the bottom of the V character. You can use a large lifting device to remove the upper whole block or composite component, then drill the rescue channel, and do not destroy the V word on both sides when drilling. Structure

The result is a change in force. When the burial pressure point is located outside the V- shape, it should support the reinforcement weak position, and then expand the hole horizontally to tap the rescue channel. It should be noted that the load-bearing wall should not be damaged when removing the components or breaking it. Cantilever type buildings are generally collapsed on the vertical wall floor and the main structure is basically intact. They can enter the interior of a building for rescue, or use heavy-duty mechanical jibs or work buckets to excavate and rescue near the burying pressure point. Mezzanine-type buildings generally collapsed and collapsed, and the rescue tunnels were mostly excavated by breaking the roof or sandwiching the upper and lower floors, and the sandwiches could be directly dismantled horizontally. However, due to the limited height of the sandwich, the operating environment is narrow, the mechanical operation is difficult to implement, and the support is bound to exist in the sandwich. If the support blocks trapped persons, a large number of lifting and support are required, and the barrier is manually disassembled. At the same time, it can make full use of the thermal expansion and shrinkage characteristics of solids (Fan Maokui et al., 2009 ), and perform alternate heat and cold treatment of steel and cement components to change their hardness and toughness and improve the effect of demolition.

In the complete collapse, the V- shape and the A- shape are different from the local collapse. The overall support needed is more than the local support. When the conditions permit, the cranes, excavators, and other heavy machinery should be used to coordinate, and the two types of structures are not Stability, the rescue process should leave a small number of people working in the upper part of the rubble, and should use small tools and manual mining methods. Compared to the V -type, the A -type collapsed components are listed in layers, and the layers are subjected to force to form a piled form temporarily. Therefore, the structure is more unstable, and pores are also easily formed. When drilling or drilling, these pores should be fully utilized, and the working surface should be small, and the operating range should be small. The type of cake collapsed collapsed, the structure was stable, and the ruins were relatively flat. It was easy to form a digging face. When the multi-layer collapses and the personnel are deeply buried, the demolition and removal work can be combined by the method of layer peeling. The removal methods mainly include manual handling, pipeline rolling, and pulling and dragging (Wang Cunliang, 2011 ). Layer removes one layer. If the collapse is a large and complete plate, column, strip, tube member, it can be removed using heavy machinery. When approaching a trapped person, the demolition must be removed from the rescue passage a few times. When the foundation sinks or the trapped person is at the bottom, the trapped person can be approached by tunneling.

3.3.3 Composite building

As complex buildings exist at the same time due to sloping and falling, they also need to be supported after excavation. Excavation uses punching or reaming methods. According to the position of the burying personnel, it is used for breaking and cutting at the top or bottom position. When using vertical well excavation or cross hole for vertical excavation, the channel route is “ L ” type, where structural stability should be selected at the inflection point, the inflection point angle should not be too small, and try to select the existing internal pores, if necessary, can form a porous Unicom.

4 conclusions

Earthquake disasters, especially destructive earthquakes, caused buildings to collapse, people were buried in varying degrees, and they were in a relatively stable living space. To grasp the characteristics of the living space of all types of collapsed buildings and carry out research on rescue techniques can greatly increase the efficiency of search and troubleshooting and the accuracy of rescue, and increase the survival rate of burying personnel. Based on previous studies on the type of buildings collapsed and types of living space, combined with the characteristics of the collapse of buildings in the Wenchuan earthquake, this paper proposes a three-level classification system for the collapse of typical buildings after the earthquake: First-grade classification is mainly based on the level of buildings and Vertical displacement, the collapse of the building is divided into tilted, collapsed, complex type; secondary classification is mainly based on the collapse direction of the building and the damaged area, the tilt type is divided into left and right tilt and front and rear tilt, slump type is divided into local collapse Falling and complete collapse; the three-level classification is mainly based on the characteristics of collapsed structures and living space structures, and draws on the popular classification theories at home and abroad to classify the secondary types into slanted, cantilevered, V -shaped, and A -shaped. , sandwich type, cake type and so on. In addition, in recent years, due to the severe earthquake disaster situation, the nation’s “people-oriented” new requirements for earthquake rescue and the research and development of new building materials, rescue technologies are facing from basic, comprehensive, inherent to fine, specialized, and motorized. change. In this regard, while summarizing the current rescue techniques, this article has carried out a review of the three-tier classification system of the stress distribution of the buildings, the distribution of the living space, the structural stability, and the survival rate of the people. The selection of rescue routes, the selection of operational surfaces, the establishment of rescue channels, and key technologies for rescue operations are discussed. In recent years, a large number of data show that the collapse type is the main type of collapse of buildings, and it is also the main cause of deep-seated pressure and casualties. Rescue techniques for collapsed buildings have become a breakthrough in improving the overall capabilities of emergency rescue. This article focuses on the detailed classification of collapsed buildings, and discusses specific rescue techniques. The next step is to conduct in-depth research on this content.

The information in this article comes from the Internet and was reorganized and edited by China Rescue Equipment Network.