Wall Failure Research Articles

Changes in the microstructure of the human aortic adventitia under biaxial loading investigated by multi-photon microscopy.

Among the three layers of the aortic wall, the media is primarily responsible for its mechanical properties, but the adventitia prevents the aorta from overstretching and rupturing. The role of the adventitia is therefore crucial with regard to aortic wall failure, and understanding the load-induced changes in tissue microstructure is of high importance. Specifically, the focus of this study is on the changes in collagen and elastin microstructure in response to macroscopic equibiaxial loading applied to the aortic adventitia. To observe these changes, multi-photon microscopy imaging and biaxial extension tests were performed simultaneously. In particular, microscopy images were recorded at 0.02 stretch intervals. The microstructural changes of collagen fiber bundles and elastin fibers were quantified with the parameters of orientation, dispersion, diameter, and waviness. The results showed that the adventitial collagen was divided from one into two fiber families under equibiaxial loading conditions. The almost diagonal orientation of the adventitial collagen fiber bundles remained unchanged, but the dispersion was substantially reduced. No clear orientation of the adventitial elastin fibers was observed at any stretch level. The waviness of the adventitial collagen fiber bundles decreased under stretch, but the adventitial elastin fibers showed no change. These original findings highlight differences between the medial and adventitial layers and provide insight into the stretching process of the aortic wall. STATEMENT OF SIGNIFICANCE: To provide accurate and reliable material models, it is essential to understand the mechanical behavior of the material and its microstructure. Such understanding can be enhanced with tracking of the microstructural changes caused by mechanical loading of the tissue. This study provides therefore a unique dataset of structural parameters of the human aortic adventitia obtained under equibiaxial loading. The structural parameters describe orientation, dispersion, diameter, and waviness of collagen fiber bundles and elastin fibers. Eventually, the microstructural changes in the human aortic adventitia are compared with the microstructural changes in the human aortic media from a previous study. This comparison reveals the cutting-edge findings on the differences in the response to the loading between these two human aortic layers.

The Impacts and Analysis of Individual and Social Risks of the Stochastic Emission of Benzene from Floating-Roof Tanks Using Response Surface Analysis and MPACT Model.

In the present study, the researchers used an integrated approach composed of response surface analysis (RSM) and MPACT model to predict fatality rates caused by benzene emitted from floating-roof tanks. RSM scenarios were configured in Expert Design (version 7.0) software using the central composite design (CCD) method and five variables of wind speed, relative humidity, atmospheric temperature, failure diameter, and emission height were considered. Continuous Pasquill-Gifford Gaussian model was used to estimate the results of the RSM scenarios. The response values were considered for exposure concentrations above 50ppm (slight damages), 150ppm (moderate damage), and 1000ppm (high damage). The analysis of individual and social risks for each scenario was done using the MPACT model in SAFETI program (version 8.22) by providing two variables of population characteristics and the frequency of tank wall failure. The results showed that atmospheric temperature, wind speed, failure diameter, and emission height have positive effects on the dispersion of the cloud of toxic benzene vapor with a concentration of 1000ppm. Intolerable individual risk distances were estimated to be lower for indoor environments than for outdoor. Maximum distances of intolerable individual risks for the worst-case scenarios were estimated up to 2500m from the emission point, which resulted from exposure to a concentration of 1000-ppm benzene. Results regarding the estimation of social risks showed that over 1600 fatalities should be expected under the worst-case scenarios. The three factors of high temperature, low wind speed, and low emission height play a major role in the occurrence of scenarios with the highest fatalities. High wind speed and high emission height were the most important factors in most scenarios with zero fatalities rate. Generally, the findings of this study show the necessity to provide an emergency response plan in the studied industry in both autumn and winter due to low wind speed. However, the coupling of the developed statistical models based on regional meteorological conditions with the MPACT model can help researchers to design an emergency response plan to deal with leakage incidents in petrochemical industries.

Shear failure of geometrically similar RC shear walls: Mesoscopic modellings and analysis

Reinforced concrete (RC) shear wall often exhibits a brittle failure pattern, which may present an obvious size effect. The objective of this study is to explore the size effect on RC shear walls with shear failure. The failure of RC shear walls having different structural sizes and aspect ratio of 1.0 was simulated by a two-dimensional mesoscopic simulated method. In 2D simulation, the concrete heterogeneities and concrete/steel interactions were explicitly considered. The mesoscopic simulation method was first verified with the available experiment observations, and was utilized to study the influences of axial load ratio and horizontal reinforcement ratio on the failure of RC shear walls having different structural sizes. The results indicate that: 1) the simulated RC shear walls present brittle failure patterns, exhibiting obvious size effect; 2) the increase of horizontal reinforcement ratio improves the shear bearing capacity of shear walls, while it would weaken or even suppress the size effect on nominal shear strength; and 3) the increasing axial load ratios improve the shear bearing capacity and lead to a stronger size effect. Moreover, a novel size effect law was proposed considering the quantitative effects from horizontal reinforcement ratios and axial load ratios for size effect.

Causes of Failure of Canal Wall down Mastoidectomy.

To identify the causes of failure of the canal wall down mastoidectomy and evaluate the causes for discharging mastoid cavity and to address the causes of failure of previous surgery to minimize the Revision surgery. This was a prospective and retrospective observational study conducted at a tertiary care hospital from May 2019 to December 2021. Total 20 Patients (11 male & 9 female) with age group (0-60 years) who previously underwent canal wall down mastoidectomy and presented with complaints of persistent ear discharge were included. All patients underwent otoscopic, oto-endoscopic and microscopic examination. Out of 20 cases,13 cases had residual/recurrent cholesteatoma, 11 cases had narrow meatoplasty and 9 cases had high facial ridge.Other causes for failure are graft defect, incomplete removal of anterior and posterior buttress. Recurrent/residual cholesteatoma and Narrow meatoplasty are most common cause for failure of previous surgery. Persistent granulation at un-exenterated area was the most common cause for suppuration. Regular follow up and cleaning of the debris from cavity enhances the epithelialization and healing of the cavity.

Modelling of CFRP-Strengthened RC Shear Walls with a Focus on End-Anchor Effects

This study first provides an overview of the development of a novel tube anchor system for the seismic strengthening or repair of reinforced concrete (RC) shear walls with carbon fibre-reinforced polymer (CFRP) sheets. The new anchor system can significantly improve the load transfer mechanism between the CFRP and supporting RC structural elements, resulting in ductile behaviour of the strengthened shear walls with increases of lateral load capacity and ductility by up to 2.6 and 8.3 times, respectively. The study then presents a new finite element modelling technique capable of capturing the complete cyclic response, i.e., from the elastic behaviour to the ultimate collapse of CFRP-strengthened RC shear walls with the newly developed tube anchor system. Two different modelling approaches are proposed to consider the effects of the tube anchor system. Additionally, other important CFRP- and RC-related mechanisms, including CFRP debonding effects, confinement enhancement, tension stiffening, compression softening, and strength and stiffness degradation under cyclic loads, are also considered in the model. By comparing the analytical and experimental results, it is demonstrated that the proposed modelling approach can accurately replicate the complex behaviour of CFRP-strengthened shear walls with a wide range of aspect ratios, from the ductile flexural behaviour of slender walls to the brittle shear failure of squat walls, without requiring detailed modelling of the anchor system.

Study on mechanical properties and wellbore stability of deep sandstone rock based on variable parameter M-C criterion

With the depletion of shallow oil and gas resources and the increase in fossil energy consumption, deep oil and gas resources have become the main driving force of economic development. However, the physical and chemical properties and rock mechanics characteristics of the deep sandstone stratum are remarkable, and there is little research on the rock failure law of the deep sandstone stratum. Therefore, a batch of sandstone with similar homogeneity was selected, and several triaxial mechanical experiments with variable confining pressure were conducted for such sandstone. The mechanical constitutive model of rock samples under different confining pressures, the macroscopic failure characteristics of rock samples, and the evolution law of wave velocity and internal energy of rock samples during mechanical loading were analyzed. According to the experimental results of triaxial mechanics, a calculation model of wellbore collapse pressure in deep sandstone formation was established based on the variable parameter Mohr–Coulomb criterion. The results show that the crack propagation process of rock samples under mechanical loading can be divided into four stages. The characteristic strength, peak strain, elastic modulus, and deformation modulus of rock samples were positively correlated with confining pressure and showed obvious nonlinearity in high confining pressure areas. The failure mode of the rock sample changed from brittle failure to plastic brittle failure with the increase in confining pressure. According to the characteristics of the stress-strain curve, the variation of acoustic wave velocity during triaxial mechanical loading can be divided into three different types. The variation trend of acoustic wave amplitude of rock samples is consistent with the stress-strain curve. With the loading of axial stress, the elastic energy curve was a concave function, the curve of dissipated energy started increasing at the cracking stress of rock samples. After destroying the rock sample, the decline slope of the dissipated energy curve decreased with the increase in confining pressure. Considering the limited failure of the borehole wall, an evaluation model of borehole wall stability in deep sandstone formation based on variable parameter M–C criterion was established. The equivalent density of borehole collapse pressure predicted using the M–C strength criterion method with variable parameters was smaller than that predicted with traditional methods. The research results provide a theoretical basis for safe and efficient drilling in a deep sandstone formation.

Seismic performance of resilient recycled aggregate piloti-type structure employing ultra-high strength bars

A resilient recycled aggregate piloti-type brick masonry structure equipped with ultra-high strength bars (UHSB) in the pilotis and shear walls was proposed. Quasi-static test and finite element analysis based OpenSees were conducted to study its seismic performance. The main parameters include different steel bar categories, reinforcement configurations, storey stiffness ratios and shear wall distributed reinforcement ratios. The results revealed that both the recycled aggregate concrete (RAC) frame-shear wall structure at the first storey and the upper recycled brick masonry structure showed satisfactory deformation performance and stable load-carrying capacity. The frame-shear wall structure at the weak first storey is prone to suffer from shear failure of the shear wall under the relatively large drift due to the larger proportion of shear deformation. The plastic damage of the pilotis and shear wall reinforced with UHSB was obviously reduced. The arrangement of diagonal UHSB in the shear wall can significantly improve the shear resistance and prevent the premature shear failure of the shear wall, and further enhance the resilience and seismic performance of the bottom-storey structure. The proposed resilient frame-shear wall structure of bottom storey presented excellent repairable performance. The innovative piloti-type brick masonry structure with resilient bottom storey can give full play to the resilience and seismic performance of its bottom-storey frame-shear wall structure even with a relatively higher storey stiffness ratio.

Structural reliability and partial safety factor assessment of unreinforced masonry in vertical bending

ABSTRACT This paper focuses on a structural reliability-based assessment of clay brick unreinforced masonry (URM) walls subjected to uniformly distributed out-of-plane loads in one-way vertical bending. Stochastic models combining finite element analysis (FEA) and Monte Carlo simulations (MCS) are used to account for spatial variability of the flexural tensile bond strength when estimating the wall failure loads. The strength of URM walls is known to be influenced by the flexural tensile bond strength, which is subject to high spatial variability as batching, workmanship, and environmental exposure alter the strength of this bond. For this assessment, single skin walls have been considered with bond strength statistics seen in typical construction. The model error statistics available for similar walls are combined with the results of the spatial stochastic FEA and probabilistic load models to determine the reliability index corresponding to the Australian Standard for Masonry Structures AS 3700 design of members in vertical bending. It was found that existing levels of reliability exceed target reliabilities, and the capacity reduction factor can be increased from 0.60 to 0.65 for URM walls in one-way vertical bending while still providing an acceptable level of reliability. A sensitivity analysis showed this finding to be robust.

It all doesn't always have to go: abdominal wall reconstruction involving selective synthetic mesh explantation with biologic mesh salvage.

SummaryThe comparative performance of synthetic and biologic meshes in complex and contaminated abdominal wall repairs remains controversial. Though biologic meshes are generally favoured in contaminated fields, this practice is based on limited data. Standard dictum regarding infected mesh is to either explant it early or pursue aggressive conservation measures depending on mesh position and composition. Explantation is typically morbid, leaving the patient with recurrent hernias and few reconstructive options. We report a case in which a hernia repaired with synthetic mesh recurred and was reconstructed with underlay biologic mesh. Delayed wound hematoma occurred after initiating anticoagulation for late postoperative pulmonary embolism, which became chronically infected. After multiple failed attempts at medical and interventional salvage of the mesh infection, the patient underwent selective explantation of synthetic mesh with conservation of the underlying biological mesh. She recovered completely without recurrent abdominal wall failure at long-term follow-up. We suggest the "salvageable" characteristics of biologic meshes may allow conservation, rather than explantation, in select cases of infection.

Behavior of thread-fixed one-side bolts bolted T-stubs with arc-shaped flange to steel tube under tension

Tensile tests and Finite Element (FE) analysis were conducted on the Thread-fixed One-side Bolts (TOBs) bolted T-stub with arc-shaped flange to steel tube in this paper. Critical parameters were determined as the thickness of tube wall, the outer diameter of steel tube, the thickness of arc-shaped flange, and the center angle between bolts. Test results revealed that the connection would encounter three typical failure modes, which were: failure mode 1, thread shear failure with yielding of tube wall; failure mode 2, complete yielding failure of tube wall; failure mode 3, thread shear failure with yielding of T-stub arc-shaped flange. Developed FE models are verified and used to analyze the yield line pattern of tube wall, the hoop stress distribution of cross-section of tube wall, and the shear acting on bolt shank. Based on the experimental and numerical results, preliminary analytical models and design methods are proposed to estimate the tensile yield strength of specimens under different failure modes.

The matrix reloaded – Addressing structural integrity of the aortic wall in aneurysmal disease

Thoracic aortic aneurysms and dissections (TAADs) involve dilation of the aortic wall that can lead to tearing or rupture. Progressive extracellular matrix (ECM) degradation is common in TAAD, regardless of the underlying cause. TAAD treatments typically target cellular signaling pathways, rather than the ECM itself, due to the complex assembly process and long half-life of ECM proteins. Compounds that stabilize the ECM are proposed as an alternative TAAD therapy that addresses the underlying cause of aortic wall failure, namely compromised structural integrity. Compounds are discussed that revisit historical approaches to maintain and preserve structural integrity of biological tissues.

Model trees and stepwise regressions for accurate in-plane shear strength predictions of partially grouted masonry walls

The behaviour of partially grouted (PG) masonry shear walls is complex due to masonry's anisotropic nature and the nonlinear interactions among its constituents. Currently available code- and research-based shear strength equations provide highly variable results when predicting the in-plane shear strength of PG masonry walls. It is crucial to develop a greater understanding in this area, as sudden shear failures of masonry walls can lead to catastrophic losses of human life and property. This study presents the development of several new in-plane shear strength models for PG masonry walls using stepwise regression and model trees with data compiled from 292 experimentally tested walls. The models are found to significantly outperform existing code- and research-based shear strength equations. It was found that, of the variables studied, the most significant ones are the axial load, wall geometry, compressive strength of mortar, and area of interior vertical reinforcement.

Landslide mechanism and stability of an open-pit slope: The Manglai open-pit coal mine

A clear understanding of landslide mechanisms and stability analyses is of great significance for landslide monitoring, prediction, and control. A large-scale end wall landslide occurred and its area reached 47,752 m2 on August 7–20, 2020, in the Manglai open-pit coal mine, China. In this paper, the engineering geological survey, mechanical test, large-deformation finite element numerical method, limit equilibrium method and analytical formula are used to analyze how the groundwater level rise caused this end wall failure and landslide. The engineering geological conditions, hydrogeological conditions, landslide activity signs and physical and mechanical parameter calibration of the sliding mass are investigated in detail and tested. Three-dimensional and two-dimensional numerical models of slopes are established, and an analytical formula calculation method to calculate the factor of safety (FoS) is proposed when sliding cracks are located on the top and toe of a slope. The results indicate that the fault fracture zone, soft strata, continuous heavy rainfall, and groundwater were the main contributors to this landslide. The three-dimensional numerical calculation results are consistent with the deformation and failure process of the slope observed in the field, which shows a retrogressive progressive failure mode. The calculation results of SLOPE/W and the analytical formula are consistent; i.e., when the groundwater level rises to +950, the stability of the end wall reaches the critical stability state. With the passage of time, the creep of the sliding surface accelerates until the entire end wall landslide.

Pull-out tests on injected steel anchors in a masonry tuff wallet

Recent seismic events demonstrated that the high vulnerability of existing masonry buildings is often related to the out-of-plane failure of perimetral walls. Lack of a proper connection with adjacent walls or slabs may favorite a premature overturing failure (first mode) significantly compromising the performance of the entire building. Nowadays, several strengthening techniques are available on the market and they are effective in increasing the connection with adjacent walls. The use of mechanical anchors made with classic (steel) or innovative (composite) materials is an effective and widely used technique. They can be often installed operating from the exterior of the building, thus reducing the disruption of the intervention and the downtime related to installation process. Although many experimental and analytical studies demonstrating the effectiveness of the injected anchors are available in literature, several aspects still need to be investigated.This research paper deals with the experimental response of injected steel anchors extracted from a full-scale tuff-masonry wall. The wall was fabricated in a laboratory environment and six anchors were extracted varying the diameter of the bar, the location (center or side of the wall) and the axial pressure.A direct comparison of the results and of the observed failure mode is reported. The main outcomes and the variability of the strength of the anchors with the main studied variables are discussed.

Paredes de alvenaria de concreto parcialmente grauteadas submetidas a cargas de cisalhamento no plano: uma revisão crítica

abstract: Although structures have been built from masonry for many years, little is still known about the behaviour of a wall subject to in-plane shear. This is particularly true of partially grouted concrete masonry. The factors that are known to affect the strength of this type of masonry are discussed with the varying results and interpretations highlighted. There is consensus that increasing axial stress increases the shear strength and reduces the ductility of the masonry. However, whether reinforcement (both horizontal and vertical) contributes to strength remains an issue of debate, as is the effect of aspect ratio. Most codes and standards do not differentiate fully grouted from partially grouted masonry, often over predicting the shear strength of the latter. Wall versus panel failure is not considered. Much work needs to be done to improve our understanding of this material subject to in-plane shear.

NATURAL PROCESSES AS JUSTIFICATION FACTORS FOR DECISIONS ON PORT HYDRAULIC STRUCTURES

The effects of sea waves and currents on harbour hydraulic structures are analysed from published open source data and the characteristics of scour from waves, including tsunami waves, are considered. Local bottom scour threatening the general stability of gravity-type engineering structures can arise under the effect of storm waves and currents, jets from ship propulsion devices and tsunami waves near hydraulic engineering structures. The types of scour mechanisms from sea waves have been investigated, i.e., local, general, and overtopping scour. There is a lack of sufficient measurement data for general scour to verify the calculation methods. Generally, general scour does not damage a structure, although it can contribute to its destruction by other types of scour when they overlap. Therefore, existing studies mainly focus on the analysis of local scour. The relationship between local scour and ground liquefaction and their influence on the stability of marine hydraulic structures is established. Failure mechanisms of hydraulic structures due to erosion by tsunami waves are analyzed: leeward and seaward toe scour, crown armour failure, parapet wall failure, sliding failure. The tsunami wave scour enhancement parameter is given, which is the fraction by which the pore pressure gradient reduces the frictional forces resisting scour. Significant ground instability occurs when the scour amplification parameter Λ exceeds a value of 0.5 (Λ ≥ 0.5). The parameter Λ can be used to assess areas where instantaneous liquefaction may be responsible for scour and sediment movement and to further recalculate erosion depths obtained without considering liquefaction. Liquefaction from a tsunami wave may penetrate up to 28% of the maximum erosion depth due to shear forces. The liquefaction phenomenon may occur due to a sudden drop in the water level in the area of return flow concentration. Consequently, the liquefaction phenomenon must be considered in the stability and erosion analysis around the structure.

Model tests of geosynthetic-reinforced soil walls with marginal backfill subjected to rainfall

A series of model tests were conducted to investigate the performance of geosynthetic-reinforced soil (GRS) walls with marginal backfill subjected to rainfall infiltration. The effectiveness of improvement measures—such as decreasing reinforcement spacing and increasing sand cushion thickness—to prevent the GRS wall failure due to heavy rainfall was evaluated. The distribution and variation of the volumetric water content, porewater pressure, wall deformation, and reinforcement tensile strain were monitored during the test. The advancement of the wetting front and the drainage function of sand cushions were visually observed using the fluorescent dyeing technique. For the baseline case, the wall began to deform as rainfall proceeded, causing the potential failure surface to gradually move backward. When the potential failure surface moved beyond the reinforced zone, the pullout of the topmost reinforcement layers occurred, resulting in the collapse of the GRS wall in a compound failure mode. Decreases in reinforcement spacing and increases in sand cushion thickness effectively reduced wall deformation and enhanced wall stability. The placing of sand cushions between the reinforcement layers can also delay water infiltration and reduce the accumulation of porewater pressure inside the wall. Suggestions for designing rain-resistant GRS walls are also proposed based on the findings.

Cyclic behavior of hollow-core precast shear walls subjected to different axial loads

To avoid the brittle failure of low aspect ratio shear walls, a novel hollow-core precast shear wall (HCPSW) with boundary elements is proposed. HCPSW has good collapse resistance and higher out-of-plane lateral resistance compared to a solid shear wall with the same concrete consumption. In this study, the effects of the axial load ratio and horizontal reinforcement on the seismic behavior of HCPSW with low aspect ratios were investigated through eight tests of full-scale shear walls under vertical and lateral loads. The results show that the HCPSW with a low aspect ratio under an axial load ratio in the range of 0.2–0.6 formed the damage development process from the hollow core to other areas of the wall panel, thus avoiding the brittle failure of the overall shear failure. The proposed shear walls consume the seismic energy through concrete cracking along the hollow core. Therefore, the higher the axial load ratio, the higher the energy dissipation capacity because of a larger damage area in the hollow core. Increasing the diameter of the horizontal reinforcement effectively improved the bearing capacity of the specimen and reduced the residual deformation. A numerical model with high accuracy was established to simulate the seismic behavior of the HCPSW and perform parametric studies.

First Report With Medium-term Follow-up of Intestinal Transplantation for Advanced and Recurrent Nonresectable Pseudomyxoma Peritonei.

To report our experience with the combination of radical surgical excision and intestinal transplantation in patients with recurrent pseudomyxoma peritonei (PMP) not amenable to further cytoreductive surgery (CRS). CRS and heated intraoperative peritoneal chemotherapy are effective treatments for many patients with PMP. In patients with extensive small bowel involvement or nonresectable recurrence, disease progression results in small bowel obstruction, nutritional failure, and fistulation, with resulting abdominal wall failure. Between 2013 and 2022, patients with PMP who had a nutritional failure and were not suitable for further CRS underwent radical debulking and intestinal transplantation at our centre. Fifteen patients underwent radical exenteration of affected intra-abdominal organs and transplantation adapted according to the individual case. Eight patients had isolated small bowel transplantation and 7 patients underwent modified multivisceral transplantation. In addition, in 7 patients with significant abdominal wall tumor involvement, a full-thickness vascularized abdominal wall transplant was performed. Two of the 15 patients died within 90 days due to surgically related complications. Actuarial 1-year and 5-year patient survivals were 79% and 55%, respectively. The majority of the patients had significant improvement in quality of life after transplantation. Progression/recurrence of disease was detected in 91% of patients followed up for more than 6 months. Intestinal/multivisceral transplantation enables a more radical approach to the management of PMP than can be achieved with conventional surgical methods and is suitable for patients for whom there is no conventional surgical option. This complex surgical intervention requires the combined skills of both peritoneal malignancy and transplant teams.

Numerical Simulation of Deformation and Failure Process of Tunnel Surrounding Rock Based on Different Constitutive Models

Based on five different constitutive models, the progressive failure process of deep hard rock was simulated, and the plastic zone, shear strain increment high-value zone, horizontal displacement, and maximum principal stress distribution of surrounding rock were obtained. The calculation results show that the plastic zone of surrounding rock calculated by MCSS and HBSS models is mainly concentrated in the floor and vault of the cavern, and the sidewall is not damaged. There is no shear zone in the surrounding rock, and the magnitude of horizontal displacement is 10-4. In the L-CWFS model, the hysteresis cohesion of friction strengthening is weakened, and the initial friction angle is 0. The calculated plastic zone runs through the surrounding rock, and the whole section is destroyed. The order of magnitude of the horizontal displacement extremum is 10-3. The MC-HB model simulates the spalling failure of the side wall, and the strain localization of the side wall is not obvious, and no shear band is formed inside the surrounding rock deeply. The N-CWFS-TSS model simulates the buckling failure process of the straight wall plate crack. A shear band is formed at the bottom of the straight wall and penetrates into the interior of the surrounding rock. The strain localization is obvious and the order of magnitude of the shear strain increment is 10-2. The calculation results are consistent with the results of laboratory tests and field observations, and the failure mechanism of the compression-shear-tensile-shear composite in the progressive failure process of the surrounding rock is clarified.