Search Results (9)

Storied Rocks (Tumpituxwinap) is a term of reference used by the Numic speaking tribal elders whom we have worked with for over 60 years on an estimated 200 ethnographic studies. Key to this analysis are the protocols for approaching, interacting, and using the places where Storied Rocks have been located. Concomitant with these traditional protocols are ones established to resolve the curiosity of non-Natives about why they are in a particular place and what they mean. This analysis shares the cultural understandings of tribal representatives who participate in these ethnographic studies. Studies used in the analysis were funded by U.S. federal agencies, supported by federally recognized Native American tribal governments, and composed with the cultural understandings shared and made public by tribally appointed elders to clarify the conundrums that are Storied Rocks. Full article

The Heimaguan Tunnel in China serves as a case study to exemplify the variation laws related to surface settlement, deformation, and stress characteristics in a shallow-buried soft-rock tunnel, while emphasizing in the tunnel support requirements. The first stage of this study begins with monitoring the time-varying characteristics of surface settlement, vault subsidence, and the horizontal convergence of Grade V rock. In the second stage, Peck theory is used to calculate the distribution characteristics of surface settlement. The results of both stages are compared to create a vault settlement model, thus establishing the horizontal convergence based on exponential function, logarithmic function and hyperbolic function, and determining the optimal time of secondary lining construction. On this basis, the time-dependent variation laws and characteristics of vertical and horizontal displacement and principal stress of surrounding rock are studied. After this, using simulation and analysis, the proper support is recommended. The study reveals that the surface settlement, vault subsidence, and horizontal convergence of the shallow-buried soft-rock tunnel stabilize within 25–30 days. Peck theory closely aligns with predictions based on exponential functions, with only a 0.72% difference. The recommended time for secondary lining application is 26–27 days. Full article

The existing tunnel structure, the new underpass tunnel structure and the rock strata in the area of influence of the crossover tunnel are interacting systems that are affected by various factors, such as dynamic and static excavation loads and dynamic and static train loads. The existing theoretical models for the deformation prediction of existing tunnels lack the synergistic analysis of dynamic and static loads on both existing and new tunnels. Based on the theory of the current layer method and Peck’s empirical formula, this paper considers the stiffness of existing tunnels, the stiffness of new tunnels, the loads of excavation methods and the loads of existing tunnels. The results show that a theoretical model for the prediction of the deformation of double-lane highway tunnels underneath existing railroad tunnels with the coupling of the current layer method and Peck under multiple factors is constructed; a modified Peck settlement formula for the base plate of the existing tunnels is put forward; and, through numerical calculations and monitoring data for validation and optimization, it is proved that the theoretical model is applicable to the excavation of tunnels underneath mountainous areas mined by the blasting method. Full article

Underground engineering construction will inevitably change the stress state of surrounding strata, which will force a negative impact on the surrounding environment, even leading to the large deformation and damage of some adjacent structures. With a focus on the deformation of a typical soil–rock composite stratum site in the construction of Changchun Metro, relying on the shield construction of a parallel twin tunnel project between Northeast Normal University Station and Gong-Nong Square Station, which belongs to the Changchun Metro Line 1, the site deformation characteristics during the shield driving process of parallel twin tunnels were studied. Based on the data obtained from field monitoring and numerical simulation, ground settlement in shield driving was analyzed, the settlement trough was studied with the Peck formula, and the action of shield driving on the adjacent tunnel was discussed. Moreover, the influence range of shield driving was suggested, and the interaction between the twin tunnels with different axis spacings in shield driving was discussed. Some regular results obtained can provide support through data for similar projects in Changchun, China. Full article

This study focuses on investigating the surface settlement characteristics induced by the construction of a super-large-diameter shield tunnel in composite strata. By utilizing a combination of field monitoring and numerical simulation analysis, the surface settlement patterns encountered during the construction process in horizontally distributed typical soil–rock composite strata were summarized based on the 16.03 m super-large-diameter shield tunnel project in the southerly extension of He’ping Avenue in Wuhan. In addition, the collected data were used to enhance the Peck empirical formula. The results of the study show the following: (1) Significant non-uniform settlement occurs along the tunneling direction when the shield machine passes through soil–rock composite strata. The range of non-uniform settlement is approximately 3.1 times the tunnel diameter (D) in soil sections and 1.9 times the tunnel diameter (D) in rock sections. (2) The impact of composite strata on the maximum settlement is greater than its effect on the settlement trough width, with a larger impact within the soil sections compared to the rock sections. (3) The Peck correction formula, which takes into account the distance between the monitoring cross-section and the composite interface, provides more accurate predictions than the original Peck empirical formula. Full article

Aiming at the features of deformation caused by large diameter vertical two-layer pipe jacking in the soil-rock composite stratum, on-site monitoring and numerical analysis has been done based on an electric power tunnel project constructed with the pipe jacking method, in which the upper tunnel is located in the soil layer and the lower tunnel is partially located in the rock layer. The research shows that: (1) During upper pipe jacking construction, the maximum transverse and longitudinal ground settlements are about three times those of the lower pipe jacking construction, and the maximum horizontal lateral displacement is about 3.3 times the lower pipe jacking construction. (2) Total ground settlement increases rapidly with the reduction of vertical clear spacing of the upper and lower pipe, and the superimposed effect should be taken into consideration during the vertical arranged pipe-jacking construction. (3) The Peck formula, which is used to estimate lateral surface subsidence distribution, is modified to make it more applicable in the soil–rock composite stratum to calculate the ground settlement induced by the construction of pipe-jacking. Full article

When a pipe roof is used as a pre-support for the surrounding rock in a shallowly buried tunnel, accurate prediction of the support effectiveness of the pipe roof is important in order to ensure the rationality of the pipe roof structure design. Based on analysis of pipe roof pre-support effects, considering the construction time of pipe roof structures and the interaction mechanisms between the steel pipes of the pipe roof and the surrounding rock, we establish a calculation model of the surrounding rock pressure acting on each steel pipe of the pipe roof on the semi-circular pre-support boundary. Through comparison and analysis with the measured results, we demonstrate that the calculation model for surrounding rock pressure and the calculation model for stress and deformation of the pipe roof are reasonable. According to the deformation coordination conditions between the steel pipe of the pipe roof and the surrounding rock on the pre-support boundary and alongside the Peck formula, we establish a theoretical analysis method for pipe roof pre-support effectiveness based on the indexes of the ground loss rate, settlement trough width, and maximum ground surface settlement, thereby realizing a quantitative evaluation of pipe-roof pre-support effectiveness. At the same time, the effects of steel pipe diameter, circumferential spacing, and excavation footage length on the pre-support effectiveness of the pipe roof are analyzed. The conclusions can be used as a basis for the design and optimization of pipe roofs and as a guide for the application of pipe roofs. Full article

Preliminary test excavations at the Hensler Petroglyph Site in East Central Wisconsin, U.S.A. have disclosed the remains of aboriginal engravings below Aeolian sediments dated to ca. 15,000 years B.P. The stratified deposits lying adjacent to an engraved panel, containing 35 pecked images, have yielded animal-like cobbles, some covered with red ochre, apparently picked for some esoteric use. The site itself has unusual natural shapes in the rock formation, along with acoustical properties, lightning strikes, a magnetic anomaly, and geographic prominence. Collectively these factors are thought to have attracted the ancient rock artists to the site. Full article

Rock-pecked images from the northern Mongolian Altai attest to the presence of human communities within the high valleys of that region during the Late Pleistocene and Early Holocene. The material provides evidence that is hitherto largely missing from the archaeological record of that region. This paper reviews the rock art, its find sites and larger physical contexts and uses evidence from paleoenvironmental studies to propose dating and cultural significance. The material is compared with other sites said to have Paleolithic imagery from Mongolia and the adjoining Russian Altai. The body of presented material offers a major resource for the study of early hunter-gatherer communities at the interface of Central and North Asia. Full article