Who invented the bulldozer?

Bulldozer is a kind of road construction machinery with shovel in front of tractor, which is used to bulldoze and level the construction site. 65438+In the mid-1970s, some people in the United States used crude horse-drawn bulldozers to level the land. 1906 Holt, the inventor of American crawler tractor, developed the earliest gasoline internal combustion engine tractor. Holt once put a shovel on a tractor as a supporting device and became the earliest bulldozer in the world. 1909, Germany began to build a large-scale expressway network. Due to World War I, the project was not completed and opened to traffic until 192 1. Germany began to use bulldozers extensively in projects. After 1945, bulldozers are indispensable and important construction methods in the reconstruction work in Britain and continental Europe and many construction projects in the United States. At present, some countries are still experimenting with an underwater bulldozer that is monitored by TV and operated by robots. Tunnel Excavator In ancient Mesopotamia, tunnels were excavated, but underwater tunnels were not successfully excavated until the19th century. When digging a tunnel in soft soil, it is necessary to prevent collapse due to the infiltration of mud and water. 18 18, British engineer brunell designed an excavator to dig tunnels under the Thames. He observed a mollusk called the ship-drilling worm, and found that the worm supported the material around the hole with a round hard shell and continued to drill forward. Inspired by this, I made a box-shaped iron shell (called a shield) and used a jack to move forward in soft soil. The excavator is digging in the iron shell and lining the inner wall of the tunnel with bricks. From 1825 to 184 1, the world's first underwater tunnel from Hu Wei to the Rosser Sea was dug with a shield designed by brunell, with a length of about 1 100 meters. 1865, British bridge engineer Barlow invented a shield and registered a patent. This shield is cylindrical, and its diameter is smaller than that designed by brunell. Instead of laying the inner wall of the tunnel with bricks, it uses iron blocks. Barlow and engineer Greathead used this shield to dig the second tunnel under the Thames in one year. Greathead also improved the tunnel excavation technology by using compressed air to offset external water pressure. 1890, London built the world's first underground railway with this technology.