About tunnels and shafts.
When you are doing something underground in the usual way, you have to defy gravity, because there is always a chance that something will fall on your head. When you are constructing a tunnel in soft soil, it can collapse; therefore, you have to provide support measures, which cost a lot of money. But if you are constructing a tunnel in hard rock, you have a different problem. You have to use explosives to excavate hard rock, which causes crack and fault zones above you. Therefore, you have to provide support (or better said, safe measures) in this situation, too.
In tunnels, the main threat comes from tunnel boundaries, but when you excavate the shaft from the surface, you have to elevate the excavated material. Even a small rock, falling from a higher level, can do a lot of damage. Safety measures define the speed and price of construction in this case.
We are currently using a whole spectrum of available technologies, from a man with a hack and shovel to giant steel worms called TBM (tunnel boring machines). In the first case, we have a one-man band, in the other, a huge team of specialized workers feeding the beast. But these are extremes; usually techniques somewhere in between are used, such as a heavy mechanization and limited numbers of workers.
All techniques require at least two steps to advance. The first step is to excavate and transport material out of the tunnel or shafts. This can be done at the tunnel or shaft face, which leaves a slice of a underground structure boundary unsupported. So, the next step must be to support this tiny slice. The second step is to install support measures on the small portion before carrying out the next step of the excavation. This is necessary because of safety and the danger of collapse, as explained in the section “About tunnels and shafts.”
There are, of course, deviations of this principle. TBM, for example, carries out both phases at the same time. Other concepts provide partial excavation and support, which allow work to be done at different places within underground structures. But all usual techniques provide an excavation of the underground structure in the advance direction only and require support of the boundaries because of stability or safety reasons. These are the main limiting factors to decreasing the costs of underground structures.
Costs of the underground constructions.
A double tube road tunnel can cost anywhere from 15,000 EUR/m (about $16,900 USD/m) and up to 100,000 EUR/m (about $112,680 USD/m). Why that much and why that kind of difference in cost?
Well, a road tunnel has to be excavated, and there is such a thing called temporary support, which ensures stability and safety during excavation. Usually it consists of concrete or shotcrete, reinforcement and anchors, and steel structures drilled into the ground. The amount of temporary support depends on geology. Then, we have to prevent water inflow, so we have to install hydro insulation. And there is a structure called final lining, which is usually a concrete tube, which ensures permanent stability of the underground structure. No wonder that costs a lot.
But why such a difference? Well, the lower price corresponds to a two-line double tube road tunnel, constructed in excellent geological conditions. If the same tunnel is constructed in bad geological conditions, the price can double because of additional temporary support. If you construct that tunnel as a three-lane tunnel in bad geological conditions, this should double the price again. And if you would like to construct even something bigger and are unlucky enough to construct it in bad geological conditions, the sky is the limit for the final price.
Deep mining and drilling.
There are gold mines in South Africa that are 3-4 km deep. There is a drill hole in Russia that is over 12 km long. And there are a lot of oil drill holes that are several km long. Those are deep penetrations to the earth’s core.
The only relatively fast way to reach the deep underground is to construct a drill hole. This is a small circular hole which must be drilled from the surface, no matter how deep it is. This is technically demanding, time-consuming, expensive, and doesn’t give adequate results if something goes wrong or the target is not there (no oil in the drill hole for example).
Geothermal energy is used for heating (in Iceland for example) and electrical energy production, but not on a large scale, which is a shame, because this is a clean and sustainable energy source. The principle of using geothermal energy is simple: there is a drill hole which serves as an injection drill hole, and another one which serves as a so-called production drill hole. In the first drill hole, we inject water at high pressure. This water goes through the ground to the production drill hole and heats up in the process. From the production drill hole, water (or steam) is pumped up and used to produce electricity in the surface.
In some places, the heat underground is much higher relatively close to the surface, and there are rock layers below and hard rock layers above. Those places are ideal for EGS (enhanced geothermal systems), in other words, power plants using geothermal energy.
Weak points of such power plants are high costs of drill holes and limited capacity of the production.
If you live underground, there is one thing which is necessary for quality of life and cannot be insured easily: daylight. Staying underground for several days or months under artificial light influence might heavily damage the health of settlers. So, is there a technique that will bring some daylight deep underground? Actually, there is. Daylight can be transferred, via cables, from a surface daylight collector to underground daylight transmitters. This is an expensive solution which has technical limitations, but it ensures at least some daylight (for example, one room where underground settlers can have their minimum amount of daylight).
Magnetic levitation is not a new thing. This is a technique which uses a magnetic field to defy the gravitational force and allows objects not to have physical contact with the surface. It is already in use, and some trains use this technique. The main advantage of this technique is that there is no friction, and theoretically, there are no limits in achieving high speed using magnetic levitation.
Space tram is a relatively old idea which refers to the initial speed used for a spaceship to reach orbit. As you go higher, the gravity force is weaker, and friction due to air is lower, so you need less energy to go higher. But of course, there are certain problems with this approach.
First, you need a long, more or less straight ramp (100 km) to achieve a decent speed (up to several km/s). That kind of speed is possible to achieve in a vacuum only, so you need an isolated ramp (tunnels or pipes). Then, of course, there is air resistance, so it is much better to fire your ship at the highest level possible to decrease it. You will also need a huge amount of energy to boost your ship. All this makes that idea not impossible, but really difficult and expensive to achieve.
It is clear that rocket transport has its limitations, including the amount of cargo that could be transported and the price for cargo transportation. It’s just not the right path going forward. So, that concept of travel to the orbit might be a good alternative.
We should get rid of cars sooner or later, or cars will get rid of us, no matter what engines they use. It’s just that simple. There are close to one billion cars in the world and close to 100 million cars manufactured each year. That’s just a big waste of resources that are limited and can be used more wisely.
Is there a possible replacement for cars? Could there be a solution which gives us all the freedom and privacy that we are used to having in cars?
My favorite idea for future transport is to have no cars, just transport vehicles on demand, driven and directed by facilities in the ground below roads. The traveler would order a vehicle, set a starting point and destination, and when the vehicle shows up, they would use it and then leave it for somebody else to use. This vehicle should also be transported through the shafts in deep transport tunnels to travel to distant locations with higher speeds. Everything should be run by a system that is able to provide the quickest possible means of travel.
There is not a clear path in the future regarding transport, so the idea above is only one of many possible solutions. At the moment, the mainstream idea is electric cars. But this is just a selling trick, if you get electricity by using coal. It’s just the wrong way to go. The solution is to rapidly decrease the number of cars and organize transport differently.
The core idea of this concept is to use smooth techniques to achieve the same result as with current techniques. But smooth also means slow, which is not good. What would be a combination of techniques which delivers results? There are a lot of possible techniques and a lot of combinations.
If you have a small, 10 cm wide, 100 m long hole, it is not really difficult to crack the boundaries of the hole. You just have to apply pressure or vibration or make a local explosion in the hole. But there is a problem: the material will crack, and remains of any size will stay at the bottom of the hole. You can’t export that material easily.
A much better approach is to produce dust or small particles on boundaries that can be extracted from the hole with a ventilator or fan installed at the bottom (or with a small pump if your transfer media is water). There is not really a problem in excavation. The problem is how to transport material to the surface.
The main idea of this article is that even small daily advancement (1.5 cm a day of widening a vertical drill hole) is enough to achieve the same speed of construction of deep shafts as we have today. For horizontal tunnel construction, where the proposed concept of excavation is far too slow, the problem is solved differently, by applying the excavation on many places at the same time, which also matches the speed of current tunnel construction technologies.
So, in our drill hole, we need equipment that is able to mill the boundaries, and we need a fan or ventilator at the bottom for small particles on the ground. How should it look?
Well, I was thinking about a steel beam of about half of the drill hole diameter, where milling devices should be rotated at different levels to cut the material. Then there should be a fan at the bottom and a bag for dust at the drill hole top.
Any contribution which covers daylight collection, transfer, and use is highly welcomed.
A molehill is an extended underground house (or underground tower block, if you like). The design allows the construction of several flats and multiple apartments. The initial proposal is to build out of cob, because according to this concept, we need to somehow use dust from excavation. How to use cob is well described in the book The Cob Builder’s Handbook by Becky Bee. The cob construction should be upgraded to industrial level, of course.
However, cob is not the best material to use in this way. It is just too heavy, so we cannot build particularly high molehills with it. The ideal material is very light material, placed in circles, which can handle pressure from a horizontal direction. So, there are other options. One option could be steel towers, similar to electrical beam towers, with the addition of wire mesh and isolation to prevent soil from getting inside. The same can be done with wood, especially a light one.
For fast construction, an expanded polystyrene (EPS) can be used. If all material is available, then the construction of a relatively big molehill can be done really fast.
So, you don’t need underground tunnels to build large underground homes. This can also be a good option if you need a decent shelter for a large group of people.
It is well known that favorable conditions like the ideal temperature, light, and humidity can rapidly increase the growth of plants. In underground places, that can be achieved, which might even have economic potential, at least for exotic plants.
There is logic to having underground barns, too. You can protect the stock and maybe even control the exhaust of methane, which pollutes the environment.
I strongly believe that underground barns can provide enough light and food and can be as or more comfortable than those that are above ground. Even underground pastures are not out of the question.
Norwegians have some crazy ideas about how to overcome the problems with traveling faster in the fjords areas, including floating road tunnels. If there is a place for such ideas, then it is not too strange to suggest a combination of shafts and tunnels below fjords, and transport with directional elevators.
For transport, long shaft conventional elevators hanging on ropes are not feasible. But there is a solution called directional (sideways) elevators, which use magnetic levitation to move, as presented by ThyssenKrupp a couple of years ago. This allowed a change of direction (vertical, horizontal), and multiple elevators in a single shaft, which might rapidly increase the capacity of such transport.