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FUNDAMENTAL EXPERIMENT ON TEST-PIECE PREPARATION AND STRENGTH TEST METHOD OF THE KABETSUCHI
Abstract
Although the mud wall has been used in many buildings from old time, the material property is still unclear. The quality of "KABETSUCHI", which is the main material of the mud wall, depends on the place of production because it is nature material. The purpose of the experiment is to estimate exactly the quality about mixing, workability, shape of test piece, compactness, and strength test of the KABETSUCHI.
... Several studies have explored the mechanical properties of wall soils. [20][21][22][23][24][25][26][27][28][29] These studies revealed that the mechanical properties of walls soil vary based on the mixing materials, mixing ratio, and fabrication conditions, such as the length of mizuawase, the period after the materials are blended and kept wet. Therefore, obtaining the mechanical properties of wall soils simulating the original materials is necessary for precise damage prediction of the wall paintings. ...
... The physical properties, including the strength of the dried and hardened wall soil, are possibly affected by the mizuawase. 20,21 Additionally, the chemical properties of wall soils, such as their elemental composition, ignition loss, the potential of hydrogen (pH), and electrical conductivity, have been investigated in previous research. 23 It has been reported that pH and electrical conductivity increased over the mizuawase period. ...
... To confirm the validity of the mechanical properties of the upper-coat soil, the results in this study were compared with those from previous research. [20][21][22][23][24][25][26][27] The mechanical properties of wall soil depend on the material, composition, fabrication methods, and other factors, such as the measurement method. Therefore, a simple comparison of test results is difficult. ...
Safe and efficient conservation of cultural artifacts requires preventing artifacts deterioration and energy‐saving environmental control. To achieve this, predicting deterioration caused by environmental conditions is necessary. Predicting the mechanical damage caused by humidity fluctuations necessitates knowledge of the mechanical properties of cultural artifacts materials. Although the mechanical properties of several artifacts have been extensively studied, no investigations have focused on the soils underlying wall paintings. This study aims to clarify some mechanical properties of the upper‐ and middle‐coat soils serving as the substrates for Hiten wall paintings at Horyu‐ji Temple. Mock‐up materials were prepared, and splitting tensile and uniaxial compressive tests were performed. Simultaneously, specimens with various equilibrium humidities were tested to clarify their humidity dependency. The tensile and compressive strengths, Young's modulus, proportional limit, and Poisson's ratio of the upper‐coat soil were 0.103–0.239 MPa, 1.16–2.55 MPa, 0.115–0.209 GPa, and 1.10–2.49 MPa, and 0.152, respectively. Moreover, the humidity‐induced strains for the upper‐ and middle‐coat soils were measured, and the moisture expansion coefficients were approximately 1240 and 2337 μST/−, respectively. The results of this study provide vital data for the conservation of the wall paintings and contribute to a deeper understanding of wall soil properties.
Wall clay test specimens using different mixing ratios and materials were fabricated using Kumamoto (Yatsushiro, Taragi, Aso, and Amakusa), Saitama, and Kyoto’s new soil and some reused soil. To understand the mechanical properties of the mud wall, a compression test and a double shear test were conducted. Then, multiple regression analysis was performed using this data to calculate the estimation formula of compressive strength (σmax) and shear strength (τmax). First, the compression test of a 150×150×60 mm block and the double shear test of a 60×60×180 mm block were conducted, and the following items were confirmed. In the new soil of Yatsushiro,
･As the compression specimen size decreased in size to a 100×100×60 mm block, the σmax and its dispersion increased.
･The σmax of the second coating soil was higher than that of the first coating soil, but τmax slightly varied. In addition, the second coating soil displayed brittle fracture behavior, but the first coating soil had a relatively higher degree of toughness.
･The σmax of some reused soil was higher than that of new soil, but σmax and τmax did not increase even when these soils were mixed.
･Even when the straw content was increased from 5% to 8%, σmax and τmax remained approximately unchanged.
･In the matured period from 7 to 90 days, σmax and τmax increased by 1.2–1.3 times.
･Even when the quantity of sand in the second coating soil increased, σmax, Young's modulus, and shear stiffness decreased.
･When the specimens were classified into coarse-grained soil and fine grained soil, the σmax of the coarse-grained soil was higher than that of fine-grained soil. However, the τmax/σmax of the coarse-grained soil and the reused soil were 0.6–0.7, that of the fine-grained soil was 0.8–1.0, and their strength ratios were classified into two groups.
･The influence of soil appeared to be significant in the new Kyoto soil.
The following results were obtained using multiple regression analysis:
･The σmax of the first and second coating soil had the highest correlation with the clay mass percentage and the water content of the mud plaster (correlation coefficient R = −0.9). τmax had the highest correlation with the plasticity index and the air-dried water content of the wall clay (R = −0.85).
･It was possible to estimate σmax using the explanatory variables of (1) and (2), where (1) is the fine sand mass percentage and density and water content of mud plaster of first and second coating soil, and (2) is the coarse fraction mass percentage, plastic limit, and air-dried water content of first coating soil.
･τmax could be estimated by explanatory variables of mud plaster density, fine sand mass percentage, plasticity index, and air-dried water content of first coating soil, but it could be also estimated by the average of σmax, which is classified as coarse-grained or fine-grained soil.
However, these multiple regression equations have a relatively low degree of general versatility because the specimen shape, the type of material, and mixing ratio are limited. In the future, we will further increase the soil type and derive a multiple regression equation of high general versatility.
This paper is to report our experimental results on static horizontal resistance for Japanese traditional mud walls subjected to static lateral force. As the first step of this study, the wall width is limited to be IP (equals to 91cm). For a mud wall frame, the resistance force is assumed to be caused by the following four factors: 1) Compressive vertical pressure force between soil wall and beam/sill at all corners, 2) Compressive vertical pressure force between soil wall and embedded horizontal wooden batten 'Nuki', 3) Equivalent friction force between wall and beam-column frame, and 4) Moment resistance force at the joint of beam and column. The static collapse experiments have been carried out to verify the validity of the assurrmtion mentioned above, where many experimental patterns have been studied with or without the factors. By the investigation on the resistance force of mud walls due to each experimental pattern, the partial degree of each factor can be clearly understood. Such results clearly indicate the degree of the lateral force capacity due to each factor for mud shear walls.
木舞壁の壁土についての基礎実験 : IV-3 促進試験
- 浦 憲親
- ほか