Indonesian experts: Dense soil, light materials vital for sturdier buildings

Published 6 October 2009

In the wake of last Wednesday’s devastating earthquake in Indonesia, experts call for more care in choosing sites for new buildings and communities; key factor: the stability of the soil; “If you build the foundation 20 to 30 meters deep, then you need very dense soil,” an expert said

The huge earthquake that rocked Padang and surrounding areas in West Sumatra last Wednesday has raised questions of how buildings in Indonesia, on the ever-volatile Ring of Fire, should be made safer. University of Indonesia geophysicist Abdul Haris told the Jakarta Post that one of the most important factors to consider before constructing a building was the stability of the soil.

If you build the foundation 20 to 30 meters deep, then you need very dense soil,” he said.

He added the earth in and around Padang was quite unstable. “The earthquake itself was strong, and the waves propagated over a large area, thus amplifying the destruction level” (see also “Earthquake-resistant Building Structure Developed,” 24 September 2009 HSNW).

Yuskar Lase, an expert on quake-proof buildings, said the general rule in construction a quake-proof building was to get a symmetrical design and use lightweight materials. He cited the example of animal pens in Yogyakarta, which withstood the 2006 earthquake. “The pens didn’t collapse because they were made of wood, which is quite light,” he said.

Yuskar added the upper part of a building in particular should be made of lightweight materials. “For example, buildings that use corrugated aluminum roofs are far safer during earthquakes than buildings that use clay tiles,” he said. He added a quake-proof building must also have rigid components that hold the entire building tightly together. “The building must not use fragile materials,” he went on. “The materials should be able to handle high loads without deforming.”

In addition, he continued, the building should be ductile and use materials that could bend under heavy loads without breaking, that is, materials that could deform. The 7.6-magnitude Padang quake leveled single-story homes and taller buildings alike.

The Jakarta Post reports that concerns have been raised over building owners and managements that shirk the government’s regulations on quake-proof construction methods. The University of Indonesia’s Sjahril A. Rahim, an expert on quake-proof buildings, said the National Standards Agency (SNI) had long drawn up regulations on quake-proof construction. “These are the regulations on quake-proof buildings that builders of all public buildings throughout Indonesia must comply with,” he told the Post. “If a building is not constructed based on these regulations, the government should not issue a building permit. This only works in theory, so of course the actual implementation of it differs.”

Sjahril added the Public Works Ministry also had issued a manual on how to make earthquake-proof houses. “I think most people still don’t know about the manual,” he pointed out. “Most houses, especially in rural areas across Indonesia, are constructed with no compliance or adherence whatsoever to the manual.”