In order to investigate the mechanical and deformation characteristics or action effects caused by vehicles and impacts on important parts of bridge or tunnel connecting sections under weak surrounding rocks especially grade Ⅳ or Ⅴ surrounding rocks

systematical indoor model tests have been carried out. The relationship among physical quantities and the similarity indexes have been worked out under the dimensional analysis method of the similarity theorem considering the characteristics of bridge and tunnel connecting projects. The model test methods such as test contents

working conditions

test equipments and instruments etc.

have been systematically analyzed and elaborated. Through analyzing the test phenomena and results

some conclusions are drawn as follows: the vehicle loads with impact actions during post operation stage cause harmful mechanical effects or structure damages on some key parts of bridge or tunnel

such as oversize displacement on bridge mid-span and lap joint tip or oversize settlement of tunnel bottom

or lower stability of surrounding rocks nearby tunnel entrance etc. Consequently

for bridge and tunnel connecting projects under Ⅳ or Ⅴ surrounding rocks

some key parts of bridge

tunnel lining and surrounding rocks nearby the entrance should be strengthened in order to avoid damages or diseases .