Hollow Brick

Japanese: 空心塼 - くうしんせん

…Bricks were widely used in the ruins of palaces in various countries during the Warring States period, for floor coverings and drainage ditches. During the Qin and Han dynasties, the basic shapes of bricks, such as square bricks, rectangular bricks, hollow-core bricks, mother-of-pearl bricks, wedge-shaped bricks, and painted bricks, were all in existence. Square bricks are square slabs, and often have patterns embossed on the surface. …

From [Brick Tomb]

…A tomb built using bricks when burying the dead. In China, during the Western Han Dynasty in the Central Plains, many tombs were built using hollow bricks (large bricks made by pasting clay slabs together into a box shape to form a board or pillar) instead of precious wood. From the mid-Western Han Dynasty onwards, the idea of creating a space underground similar to the living space above ground became popular, and the space of tombs expanded. …

*Some of the terminology explanations that mention "hollow core brick" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…戦国時代の列国の宮殿址では，塼が多用されており，床敷きや排水溝に用いられている。秦･漢時代になると方塼，長方塼，空心塼，子母塼，楔形塼，画像塼など塼の基本形が出そろう。方塼は正方形の板状を呈し，表面に文様を型押しする場合が多い。…