Though many claim that Trump's Mexico-America wall is merely a "metaphor" for greater immigration vetting, he has said explicitly, multiple times, that he intends to build that wall. Many have been begrudgingly entertained by the back-and-forth over whether or not Mexico will pay for the wall, but it becomes more and more clear that Trump has every intention of making an actual wall to prevent illegal immigration. But very little has been said about the exact dimensions and resources needed for the wall. Imgur user Ali F. Rhuzkan uploaded a rather comprehensive summary of what such a wall would require.
In this summary, they begin by stating such a wall would need to go 5 feet underground - to prevent tunneling - and be at least 20 feet tall - to prevent climbing.
After describing how brick and mortar would be too intensive, and steel wire would be an easy to penetrate fence (And Trump has been quite particular about this being a "wall"), concrete is decided upon to be the most likely material for the wall.
Since the high heat of the desert areas would be a problem for the concrete curing process, most of the construction would need to be done off-site and delivered to the border. This method is a rather common system, according to this engineer:
"This design consists of I-shaped concrete columns spaced at 10 feet on center, with eight-inch-thick wall panels spanning in between them. In such a design, the only concrete that would need to be cast on site would be for the foundations. The columns would be anchored to the foundations, and the wall panels are slipped into place from above."
And here is the mathematics of the whole wall:
Foundation: 6 feet deep, 18 inch radius = 42.4 cubic feet
Column: 4 square feet area by 30 feet tall = 120 cubic feet
Wall panels: 25 feet tall by 10 feet long by 8 inches thick = 166.7 cubic feet
Total concrete per 10-foot segment = 329.1 cubic feet
1,954 miles = 10,300,00 feet = 1,030,000 segments (10-feet long each)
1,030,000 segments * 329.1 cubic feet per segment = 339,000,000 cubic feet = 12,555,000 cubic yards. (The cubic yard is the standard unit of measure of concrete volume in the United States.)
12.5 million cubic yards just in concrete.
For perspective, this amount is roughly equal to 3 TIMES that of the Hoover Dam (4,360,000 cubic yards of concrete).
This amount of concrete could be used to create a highway going from New York to Los Angles - going the long way AROUND THE EARTH.
The Panama Canal, an internationally funded and worked upon project, only required 5,000,000 cubic yards of concrete.
The only other construction project on this scale is that of the Three Gorges Dam in China, which comes in at 21 Million cubic yards of concrete - and that dam affected the earth's rotation.
However, it must be said that most of these other projects had noticeably positive effects upon their communities, either in energy production, trade efficiency, or ease of travel. We cannot be sure of the benefits of the wall until we have confirmation that climbing a little bit higher or digging a little bit lower are not possible.
