Ground bearing capacity calculation is a comprehensive task that involves various fields such as structural mechanics, materials science, and design standards. I am an outsider to civil engineering and cannot provide more detailed explanations. I have a saying: technology originates from life, and ultimately, technology should serve life. Today, let's not discuss specific calculation formulas but instead talk about everyday scenarios to see if my observations and summaries are correct.
My home is located on the southern slope of Snow Peak Mountain in central Hunan, where the seasons are distinct. The terrain in Hunan is higher in the south and lower in the north. In winter, the wind blows from the north, and before global warming, it used to be described as a biting cold wind. When I was young, "seventh month, see the cattle boys walking on the field ridge" (a local dialect expression) marked the time when the weather began to turn cold, and we could wear coats in the mornings and evenings. The grass along the roadside would already be covered with dew, and by mid-autumn, the grass would begin to frost. There's a saying, "after autumn, the locusts are frozen like eggplants." By the lunar October, the north wind would howl, and rain or snow would fall-sometimes it was snowflakes (pure snow), sometimes sleet (snow mixed with rain), or freezing rain (rain that froze midair). Water would freeze in small pits or animal tracks along the road. Some pits were smaller than shoes, and could be broken by stepping on them with the tip or heel of the foot. But when the ice became thicker and could no longer be broken, even with a strong stomp, the ice would have been thick enough for skating on ponds. A folk method of judgment is that if children can walk on the ice but adults cannot break it, then adults can walk on it too.
Later, due to climate warming, since the 1990s, it has become impossible to skate on ponds because the ice is no longer thick enough. I used to think we had experienced enough cold, but after working and traveling to the northeast, I finally realized what true ice and snow are like-there, even cars can drive on frozen rivers. Whenever I get the chance, I go to frozen rivers or lakes, and the scene takes me back to my childhood. Below is a photo I took near my hotel in Changchun during a business trip in 2017. Can the locals recognize where this is?
Also, we often see bridge weight-bearing signs along highways. Some short bridges only show axle weight, while longer ones show both axle weight and total vehicle weight. On highways and elevated expressways, even the largest trucks can pass without trouble, but on city overpasses, trucks are often prohibited.
Next, let's compare the ground wear marks left by the test vehicle used by our company. The vehicle's wheel system consists of diagonal nylon wheels and diagonal drive wheels.
In the picture above, the nylon wheels are harder than polyurethane wheels and have a smaller width, so they cause more significant damage to the ground, showing noticeable crushing damage. But does this necessarily mean the ground bearing capacity is insufficient? In conclusion, do we get influenced by other interfering factors when evaluating bearing capacity?
Below are the definitions of strength and hardness from Baidu Encyclopedia for reference.
1.Different definitions: Strength refers to a material's ability to resist failure under external forces, including tensile strength, compressive strength, and flexural strength. It concerns whether the material can maintain integrity and avoid fracture or excessive deformation when under load. Hardness, on the other hand, is a material's ability to resist penetration by a hard object on its surface, such as Mohs hardness or Brinell hardness.
2.Different research objects: Strength studies the internal force distribution, structural organization, deformation, and failure characteristics of materials under external forces. It focuses on the reliability and stability of materials when bearing loads. Hardness primarily studies the material's surface change when a hard object applies force to it.
3.Different measurement methods: Strength is measured through static tests, tensile tests, and other methods using standard specimens. Hardness measurement methods vary depending on the type of hardness, including static pressure, scratch tests, rebound tests, and others, such as microhardness or high-temperature hardness tests.
Common points between strength and hardness:
1.Both are important indicators of a material's physical properties, reflecting its resistance to external forces. Strength typically describes the maximum stress a material can withstand before deforming or breaking, while hardness measures its ability to resist local plastic deformation (such as scratches or indentations).
2.Both strength and hardness impact the material's performance and service life in real-world applications. Materials with high strength are suitable for structural components that must withstand heavy loads or impacts, such as bridges, buildings, and aerospace equipment. Materials with high hardness are suited for wear-resistant and abrasion-resistant applications, such as cutting tools, bearings, and precision instruments.
3.Both strength and hardness are influenced by a material's internal microstructure. For example, the grain size, impurity content, and grain boundary structure in metal materials all affect their strength and hardness. By measuring strength and hardness, we can indirectly understand the material's internal structure and quality.
For example, ice and steel are both hard, but steel is stronger.
