River pebbles pave the eight trigrams pattern

Quick answer：

The 'eight trigrams pattern' refers to the Ba Gua, a fundamental concept in Chinese philosophy and divination. It is a system of eight symbols, each representing a combination of three lines - unbroken (representing heaven) and broken (representing earth). River pebbles are often used in Chinese gardens to symbolize stability and the passage of time, and they can be arranged to form various patterns, including the Ba Gua. This practice reflects the Chinese cultural appreciation of natural elements and their philosophical significance.