Wenchuan, Sichuan Province, China, Earthquake of 2008: Lifeline Performance

This chapter summarizes the report from the 2009 Technical Council on Lifeline Earthquake Engineering (TCLEE) Conference, held in Oakland on the subject of lifeline earthquake engineering in a multihazard environment. Starting with a sketch of the Wenchuan earthquake that caused widespread and extensive damage to critical infrastructure lifelines, the report discusses the following lifeline systems: electric power, communication, water and wastewater, highways and bridges, airports, railways, schools and building stock, and emergency response. This chapter describes how the report's chapters are organized, starting with an overview of the system's performance; a description of the system, its damage, emergency response, and recovery; conclusions and recommendations; and a synopsis of the emergency response lessons learnt.

The Wenchuan, China, Richter magnitude 7.9 earthquake was one of the most damaging in the last several hundred years in a country that has documented many devastating earthquakes during the past 700 years. The Chinese authorities have rated the Sichuan area as a somewhat low seismic hazard zone, and the design code for engineered structures suggested a design level of PGA = 0.10g. Landslides were prevalent wherever ground motions exceeded PGA = 0.35g or so. The surface faulting had a maximum vertical uplift of about 2 m with a length of about 30 m. Construction sites are divided into four classes according to the equivalent shear wave velocity for surface soil layers and the overlaying thickness at the site. The seismic effect coefficient of a building structure is determined based on the class of design earthquake, site class, and natural period of a structure.

The Wenchuan earthquake occurred in a mountainous region where landslides caused damage to roads and railway lines. Road damage was due to rockfalls, avalanches, landslides, debris flow, liquefaction with lateral spreading, quake lakes, surface rupture, and collocation effects. At the time of the earthquake, the only road between Dujiangyan and Yingxiu was Provincial Highway 213. The earthquake almost completely destroyed the existing highway, the Miaoziping Bridge on the new expressway partially collapsed, and the Longxi tunnel was damaged. Many rockfalls, landslides, mudslides, debris dams with flooding, and surface faults occurred on the road between Wenchuan and Qingchuan. With the type of upgrade strategy discussed in the chapter, keeping most roads, rails, tunnels, retaining walls, bridges, and other transportation facilities in service for smaller earthquakes and limiting the damage from very large earthquakes should be possible.

Generation, transmission, and distribution of electrical power in China uses systems that are similar to those used throughout the world. Power sources include thermal (nuclear, coal) and hydroelectric power. The Sichuan Province State Grid has estimated that the cost for repairs and replacements to the electric system as a result of the earthquake will be 31.3 billion RMB. Substantial damage to low-voltage distribution systems and to high-voltage substations was observed. The major city of Sichuan, Chengdu, retained electrical power, while many other zones nearby had power outages. Widespread damage to high-voltage substations occurred due to strong ground motion, and damage to transmission towers resulted from landslides. Many high-voltage transmission towers were partially or completely damaged in the earthquake.

This chapter overviews the existing water systems. Townships, village governments, or groups of homeowners operate the wells and spring water collection systems. In larger cities, such as Dujiangyan, where damage to buildings was sporadic, individual buried pipes were repaired, and new pipes were limited to evacuation zones with newly installed above-ground water pipes. One report described damage to water treatment plants with structural cracks in the building walls; however, the plants apparently remained in operation. In a major disaster with extensive destruction of homes, water system recovery includes two progressive steps: (1) providing water to central locations and temporary housing locations, such as disaster control centers and tent encampments, and (2) repairing and recovering the existing water systems.

Three factors negatively affected the performance of the telecommunication systems in the earthquake-devastated areas during the Wenchuan earthquake. The first was the increased call volume, which impaired the network. The second factor was the long duration of electric power outage in most remote areas. Third, telecommunication equipment buildings, switching offices, cell sites, equipment, and cellular towers were damaged. One of the major service providers in Sichuan suffered damage to more than 600 equipment buildings and 6,000 km of optical fiber cables. Massive landslides and rock falls and damaged bridges and buildings contributed to landline failures. A team of earthquake research engineers from the Institute of Engineering Mechanics (IEM) and many other universities in China performed a field investigation within two weeks of the earthquake. The data collected can help earthquake engineers mitigate future damage and save lives.

The Richter magnitude 7.9 Wenchuan earthquake of May 12, 2008, was one of the most costly and damaging earthquakes in recent memory. This chapter looks at damage to dams in the Sichuan region, including Zipingpu Dam near Duijanyan, Shapai Dam, and others damaged by the Wenchuan earthquake. The chapter offers lessons learned regarding the design, construction, operation, and maintenance of these structures, comparing Chinese dam design and safety practices with U.S. dam design and safety practices for earthen, concrete, and rockfill dams. The Wenchuan earthquake provided engineers who work on dam design and dam safety issues invaluable insight into the performance of both high- and low-head and earthen and concrete dams.

The collapse of schools and the fatalities of school children in the Wenchuan earthquake were devastating. Central Beichuan experienced major landslides and rock falls, blocking the only road accessible to the remote villages in the township of Hongkou. Dujiangyan, one of the major cities in the earthquake area, sustained heavy losses in property damage and human lives. Close to 95% of the buildings in Yingxiu town were destroyed. Access to the town was cut off due to collapsed bridges, tunnels, and landslides covering roads. Chengdu, however, did not experience any strong earthquake motion. Most of the residential buildings in Shifang, which are small URM-type buildings, were severely damaged or collapsed. Hejiaba is a very small village across the river from Nanba. The fault that runs under this village ruptured during the earthquake.

The Wenchuan earthquake was a once-in-a-lifetime disaster that affected a large area in the mountainous region of central China. The Chinese government was challenged with the need for immediate response, including search and rescue, restoration of lifelines, debris removal, and response plans to this mega event. Due to the earthquake's magnitude, the Chinese government was willing to accept assistance from the international community. The United Nations (UN) responded immediately by making a contribution through the Central Emergency Response Fund (CERF). To help stabilize society in the damaged areas, the Chinese government allowed the media to keep the lines of communication open about the disaster. The Chinese government is taking great steps toward the prevention of such monumental losses from potential future disasters.