EXPERIMENTAL STUDY ON PHYSICAL AND MECHANICAL PROPERTIES OF TRAVERTINE IN BOLIVIA

Travertine is a kind of macroporous secondary calcium carbonate, formed by Karst water. Travertine can create beautiful natural landscapes such as the Huanglong scenic spot in China, the Pamukkale in Turkey, and the Yellowstone Park Mammoth Hot Springs in the United States. While travertine is mainly distributed in the carbonate areas with frequent water flow, it is rarely used as foundation of buildings and its engineering characteristics are less studied. The project location is in Bolivia, South America, where a steel plant is to be built upon a Travertine land. The travertine in this area is formed by the lacustrine facies, grayish-white, visible honeycomb-like or spongy voids, with some of the voids filled with clay. The SPT N value of the travertine is 39 to 77, which has good mechanical properties in the natural state. But when the travertine is submerged in water, it collapses quickly. Rain in Bolivia lasts for four months annually, it is worried that rain can damage the travertine foundation. A study is thus conducted to test the properties of travertine in the construction site. It is found that the permeability of travertine is 1.7×10^-3cm·s^-1. The load test is divided into two groups, P1 and P2. The P1 test point is used to test the bearing capacity and collapsibility under the condition of immersion. P1 is soaked in water before the test, and the water head height was 30 cm for 5 days. The P2 test site is used to test the elastic modulus of the natural state and evaluate the collapsibility. In both tests, the first load is kept to 200 kPa and then the test pit is injected water evenly, with a constant head height of 30 cm. The results show that the deformation modulus of the travertine can reach 45.39 MPa in natural state and 36.85 MPa in immersion state; that the foundation bearing capacity is more than 280 kPa in immersion state; and that the depth of infiltration is 0.65 m after 3 hours of immersion. It is concluded that the stability of the travertine in water is poor and the construction in the dry season is recommended. The bearing capacity of travertine is sufficiently high in natural condition but reduced somewhat in case of immersion so that the base should be kept dry as far as possible. The permeability of travertine is small. If the foundation is waterproof in rainy seasons, it keeps a sufficient bearing capacity.