As an important outdoor cultural relic, the grotto temple is affected by the dry-wet cycles caused by rainfall, water seepage and other natural environment for a long time, As a result, the deterioration of physical and mechanical properties is induced, causing instability damage. In order to better protect grotto cultural relics, the sandstone of Dazu stone carving grottoes is selected as the research object. Experimental research on the strength deterioration characteristics of grotto sandstone under the action of dry-wet cycles is carried out through uniaxial compression test and Brazilian split test, and the influences of dry-wet cycles combined with immersion in solutions of different pH values are analysed. The results show that: (1) The uniaxial compressive and tensile strengths of sandstone after complete drying are improved compared to the natural state. (2) The mechanical properties of the sandstone deteriorate after several dry-wet cycles. With the increase of the number of cycles, the deterioration gradually increases. When the dry-wet cycle reaches a certain number, the impact on the strength of sandstone is weakened. (3) Different pH values also affect the degree of sandstone deterioration. The lower pH value will induce more serious deterioration of the sandstone mechanical properties. (4) After several dry-wet cycles using acidic solutions, the sandstone damage form changes compared to that in the natural state.

Grotto temples are important historical relics, and their protection and utilization are becoming increasingly important. However, under the effect of cooling and heating for a long time, the physical and mechanical properties of the grotto rock mass will change in a certain. In this paper, the sandstone of Dazu grottoes in Chongqing was taken as the research object, and the deterioration properties of the grotto sandstone were studied through the mass, longitudinal wave velocity test, CT scanning, X-ray diffraction (XRD), X-ray fluorescence (XRF) analysis. The experimental process involves multiple conditions such as different heating-cooling cycle times, different durations of high and low temperatures, and different cooling methods. These test conditions are designed to analyze the effects of different temperature changes on the quality, longitudinal wave velocity, fracture development, mineral element composition, and internal pores of grotto sandstone. The results show that: (1) The longitudinal wave velocity of sandstone decreased after multiple heating-cooling cycles. The degree of reduction was influenced by the number cycles and the cooling methods. (2) As water cooling method was used during the experiment, soluble salt minerals in sandstone would gradually lose, which leaded to an increase in pore size of the rock sample and the formation of cracks.

Current research on the thermodynamic characteristics of the energy pile group foundation under external load mainly focuses on the vertical load, however the study on impact of horizontal load is limited. To investigate the deformation characteristics of horizontally loaded energy pile groups under asymmetric heating or cooling conditions, a single pile within the 2×2 energy pile group was heated and cooled through the model tests, and a three-dimensional finite element model of the energy pile group was established. The measured data and numerical results were compared and validated, and parametric analysis was conducted to study the thermo-mechanical response of the pile during the operation of a single pile for the energy pile group. Results indicate that the findings of numerical model and model tests are generally consistent. The bending moment was mainly concentrated in the upper part of the pile, its peak bending moment and inflection point are located 0.23L₁ and 0.8L₁ below the soil surface, and the horizontal displacement of the pile also decreased with the increasing depth (L₁ is the effective buried depth of pile). The horizontal loading had a greater impact on the deformation characteristics of the pile, but the influence of temperature could not be ignored. As the temperature increased or decreased, the bending moment and displacement of the energy pile tended to increase. Compared with the only subjected to horizontal load, the increase in water temperature by 10 ℃ and 20 ℃ led to an increase in the M_max (peak bending moment) of the energy pile by about 23.36% and 25.46%, and an increase in the horizontal displacement of the pile top by about 20.59% and 21.93% when the horizontal load and temperature variation were applied simultaneously. The decrease in water temperature by 10 ℃ and 20 ℃ resulted in an increase of approximately 23.48% and 24.39% in the energy pile M_max (peak bending moment), and an increase of approximately 17.97% and 21.27% in the horizontal displacement of the pile top.

The rock mass of grotto temples, exposed year round, is influenced by natural factors, especially temperature fluctuations and water seepage, which change the rock ’s physical properties. This paper investigates the permeability characteristics of Dazu grotto sandstone(Chongqing) after multiple heating-cooling cycles. Permeability tests are conducted under various conditions, such as cycle frequency, high temperature exposure durations, and cooling methods. Results show that sandstone permeability increases with heating-cooling cycles, influenced by the number of cycles and cooling methods. High permeability pressure also reduces sandstone’s compressive strength compared to low permeability pressure.