thank you for contributing to this thread. I provide below my analysis of what I think the function of the girdle stone was. Below I have a few bullet points and some simulations in Ansys at the end, let me know what you think.
1) The granite plugs weight around 7 tones and were held in the Grand Gallery before slid down the ascending passage .
2) When slid down, they would accelerate along the length of the ascending passage before reaching the junction where ascending and descending passage meet. Based on the length, weight, inclination and speed, I estimate the plugs would
accumulate at that point around 1,000,000J of energy. To put this in perspective, this is about as much energy as a car would have running at a speed of 90 miles per hour and hitting a wall. That is too much energy to handle for the junction. Most likely at that speed, a granite plug would take significant portion of the stone work there. The first plug would put stress, two others following the first would finish the job.
3) As I explained in this paper . I believe the granite plugs worked as an emergency stop in the pyramid. The granite plugs would slid down and block hydrogen gas passing through to the Queen's chamber. Someone would be relying on this portion of the system to work flawlessly in case emergency shutdown is needed. Possibility of the damage at that point would not be acceptable. Looking at all perfection in the pyramid it does not appear anything in this system is left to the chance. So, the builders needed to develop the intelligent way to control the speed of the granite plugs.
4) When plugs are slid down the ascending passage, the friction would work to slow those down. Though, I doubt much would be present. With moisture trapped in the pyramid, most likely, the surfaces would be covered with biofilm. The plugs would slid on the surface with least resistnace as fast as rock on ice.
5) Not many know, but granite material can be magnetic. What makes it magnetic not Sio2 (or Quartz) present in the granite but other minerals which make up about 40% of the granite. The red granite taken from the Abu Rawash area was analyzed in this paper . Four samples were taken from different deposits. The chart of minerals present in the paper shows significant content of the ferrite. What it means is the granite plugs which are made of the red granite when exposed to magnetic field would get magnetized. Also, the girdle stones are made of limestone. This material is not a good conductor but it depends on its composition and moisture content .
6) People are still writing PhD dissertations on certain aspects of the Lenz's force but basic idea is summarized on this page . The magnetic material passing through the coil made of conductive material, induces current in the coil which creates magnetic field opposing the magnetic field of the magnet. All this means that when the granite plug slides through the girdle stone there will force acting on the plug slowing it down.
7) I ran a few simulations in Ansys to demonstrate this (See animation here ). A granite plug slides down the ascending passage, passing through the girdle stone. Note the speed of the plug slows down as it gets close to the stone. Only one stone is simulated here but all others present in the ascending passage would have similar impact on the speed. One other thing to mention, the faster plug slides more force is acting on it trying to slow it down. The lesser is the speed, the lesser is the force. So, essentially this technique controls the speed of the granite plugs regardless of the condition of the surface floor (moisture, biofilm) which the builders of the pyramid for sure could not predict over the millennia the pyramid could be in use (which I have no doubt was the plan).
8) As Jon mentioned above, the girdle stones are made of different materials. The best effect on the speed would be achieved if the girdle stones are isolated from each other. A simple way to achieve that would be to sandwich girdle stones made of conductive limestone between layers of the non-conductive limestone (Tura limestone would be a good material for that). This may be one reason why builders used different limestone in that portion of the pyramid.
 Alen Alford "Pyramid of Secrets: The Architecture of the Great Pyramid Reconsidered in the Light of Creational
Mythology" Feb 24, 2003, ISBN-10: 0952799421
 Atef El-Taher "Rare Earth Elements in Egyptian Granite by Instrumental Neuron Activation Analysis" 2006
 Marzouk M. Bekhit, Saad A Khalil “Electrical Properties of Moist Limestone Samples
In The Frequency Range 1Hz-10 Hz From Abu Rawash Area” Australian Journal of Basic and Applied Sciences, 1 (4): 741-750,
Edited 2 time(s). Last edit at 17-May-18 00:03 by kborissov.